A calculation method for laminar flame center and flame propagation radius

Abstract

The present invention discloses a method for calculating the center of a laminar flame and the flame propagation radius. A flame pattern image is taken under initial experimental conditions, and the image is superimposed with a group of flame pattern images taken after the ignition electrode is rotated by 90° under the same initial experimental conditions. The best flame superposition image is determined, and the initial center of the flame edge contour in the two superimposed flame contour images is calculated. The range of the flame edge contour affected by the ignition electrode is determined, and the flame contour affected by the ignition electrode in another flame contour image is replaced with the edge contour without the influence of the ignition electrode. The center coordinates of the flame in the two flame pattern images after the influence of the ignition electrode is removed and the flame radius at each angle are calculated. The present invention aims at the influence of the ignition electrode on the flame edge contour, and uses the edge contour with high correlation to replace the area affected by the ignition electrode, so as to obtain a better flame edge contour and reasonably calculate the flame center and the flame propagation radius.

Description

Technical Field

[0001] The invention relates to the technical field of laminar flame combustion, and in particular to a method for calculating a laminar flame center and a flame propagation radius. Background Art

[0002] Studying the laminar flame radius is the basis for studying the laminar flame combustion characteristics, and the laminar flame combustion characteristics are the basis for studying and describing the characteristics of premixed turbulent flames. Therefore, a more accurate laminar flame radius is also the cornerstone for further studying the characteristics of premixed turbulent flames. In recent years, in order to further study the laminar combustion characteristics, domestic and foreign scholars have begun to use spherical expansion flames based on a constant volume combustion test platform to measure the instantaneous radius of laminar flames at different times, so as to study the laws of laminar combustion characteristic parameters. However, due to the unevenness of laminar flame propagation, the processing technology of schlieren images and improving the measurement accuracy of flame radius are particularly important for the study of the regularity of laminar combustion rate, and are also crucial for the quantitative study of laminar flame combustion characteristics. Through a series of analyses of spherical expansion flame schlieren images based on constant volume combustion bomb research, many scholars have confirmed that the ignition electrode is one of the main reasons for the distortion of flame propagation in its direction.

[0003] In response to this problem, scholars have proposed a variety of optimization methods for flame radius measurement, such as the equivalent circle area method. However, this method has inevitable defects. For the equivalent circle area method, the area enclosed by the edge pixels of the flame front is equivalent to a circle. The position of each pixel cannot affect the calculation result of the flame radius alone. Only when the convex or concave area of ​​the local flame surface accounts for a certain proportion, the calculation result of the flame radius will be affected. However, due to the influence of the unevenness of laminar flame propagation, the equivalent circle area method cannot well characterize the radius changes in all directions, and there will be large errors when studying the laminar flame combustion characteristics. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method that can more accurately calculate the laminar flame center and the flame propagation radius, which can further eliminate the influence of the ignition electrode on the flame center and the flame propagation radius, thereby increasing the accuracy of laminar flame combustion characteristics research.

[0005] A method for calculating the center of a laminar flame and the flame propagation radius comprises the following steps:

[0006] Step 1: When the initial experimental conditions are selected, ignite the flame through the constant volume combustion bomb ignition electrode, take a flame pattern image, and obtain a flame pattern image at a certain moment;

[0007] Step 2: After rotating the ignition electrode by 90°, repeat the experiment to obtain a set of flame pattern images;

[0008] Step 3: pre-processing the flame pattern images obtained in step 1 and step 2 to obtain edge contours of the flame pattern images of each image;

[0009] Step 4: Determine the geometric center of the flame pattern image as the base point, and superimpose the flame pattern image obtained in step 1 with the flame pattern image obtained in step 2 at the base point in pairs;

[0010] Step 5: Process and analyze the obtained superimposed images respectively, determine the most ideal flame superimposed image based on the minimum percentage error of the length from the edge point on the midline to the origin, and extract the first flame outline image and the second flame outline image from the most ideal flame superimposed image;

[0011] Step 6: Determine the initial center of the flame edge contour in the first flame contour image and the second flame contour image respectively;

[0012] Step 7: Determine the range of the flame edge contour affected by the ignition electrode and calculate the relevant data;

[0013] Step 8: replace the flame outline of the first flame outline image affected by the ignition electrode with the edge outline of the second flame outline image without the influence of the ignition electrode; replace the flame outline of the second flame outline image affected by the ignition electrode with the edge outline of the first flame outline image without the influence of the ignition electrode; obtain two flame schlieren images of the flame after removing the influence of the ignition electrode;

[0014] Step 9: Calculate the center coordinates of the flame in two flame pattern images after removing the influence of the ignition electrode;

[0015] Step 10: Calculate the flame radius at each angle of the two flame schlieren images after removing the influence of the ignition electrode.

[0016] Furthermore, the step 2 is specifically as follows:

[0017] Step 21: While ensuring that the conditions of the constant volume incendiary bomb body remain unchanged, only the ignition electrode is rotated around the geometric center of the shooting plane, so that the position of the ignition electrode after rotation forms an angle of 90° with the position of the ignition electrode under the conditions of step 1;

[0018] Step 22: Perform the experiment again using the initial experimental conditions set in step 1, and take a flame pattern image under this condition;

[0019] Step 23: Select the flame schlieren picture obtained in step 22 at the same time as step 1;

[0020] Step 24: according to the shooting time of the flame pattern image obtained in step 23, obtain N flame pattern images with the same shooting interval before and after the shooting time, N = 1, 2, 3...;

[0021] Step 25: Summarize the flame pattern images obtained in step 23 and step 24, totaling 2*N+1 flame pattern images.

[0022] Furthermore, the geometric center of the flame pattern image is determined in step 4 as follows: according to the pixel size of the flame pattern image, the four endpoints at the upper, lower, left and right boundaries of the flame pattern image are obtained, and the intersection of the two diagonal lines formed by connecting the four endpoints is taken as the geometric center of the flame pattern image.

[0023] Furthermore, the step 5 is specifically as follows:

[0024] Step 51: Based on the two-dimensional coordinate system, define the flame region of the flame pattern image at 0°-180° as region 1, and define the flame region of the flame pattern image at 180°-360° as region 2;

[0025] Step 52: Take the midline of the angle formed by any two adjacent ignition electrodes in region 1 of each superimposed image, and the midline intersects the two edge contours in region 1 at pixel points A0 and B0, and intersects the two edge contours in region 2 at pixel points C0 and D0;

[0026] Step 53: Calculate the distances from the pixel points A0, B0 and the pixel points C0, D0 to the origin O respectively;

[0027] Step 54: Calculate the percentage error of the lengths of OA0 and OB0 in area 1 and the percentage error of the lengths of OC0 and OD0 in area 2 according to the percentage formula;

[0028] Step 55: Taking the center line as a reference, draw 10 straight lines in clockwise and counterclockwise directions through the origin O with a step length of 1 degree;

[0029] Step 56: Take the moment when the straight line intersects the two flame edge contours at the same time and record the pixel point A m , B m With C m , D m , m=-10,…,-1,1,…10;

[0030] Step 57: Based on the distance formula Calculate the length from the edge pixel point to the origin O at each angle in step 56, and then compare the percentage errors between the lengths;

[0031] Step 58: Calculate the arithmetic mean of the percentage errors of the lengths from the edge points to the origin at all angles obtained in step 54 and step 57; and take the flame superposition image with the smallest arithmetic mean as the most ideal flame superposition image.

[0032] Furthermore, the step 6 is specifically as follows:

[0033] Step 61: re-establishing an initial two-dimensional coordinate system for the first flame outline image and the second flame outline image based on the pixel origin of the flame schlieren image;

[0034] Step 62: obtaining the maximum and minimum pixel points E1 and E2 on the ordinate of the first flame outline image, and the maximum and minimum pixel points E3 and E4 on the abscissa, and then obtaining the endpoints F1 and F2 of the positive and negative electrodes of the ignition electrode;

[0035] Step 63: draw four straight lines tangent to the edge contour through the edge maximum point, the four straight lines intersect with the four endpoints of the matrix, and draw two diagonals of the matrix intersecting at the geometric center G; connect the endpoints F1 and F2 of the positive and negative electrodes of the ignition electrode, the midpoint of the line connecting the endpoints is the ignition electrode center H, and then draw a line connecting the two end points G and H, the midpoint M of the line is the initial flame center;

[0036] Step 64: Draw a straight line through the initial flame center M in a clockwise direction at a fixed angle. When the straight line intersects the flame edge contour at the same time, i With Y i When the coordinates of its midpoint are i =(X i +Y i ) / 2;

[0037] Calculate each correction radius measurement center Q i The average value of the coordinates of the initial flame center M and the initial circle center coordinates (x0, y0) is obtained:

[0038]

[0039] In the formula, n represents the number of straight lines drawn with a fixed angle as the step length;

[0040] Step 65: Based on the calculation formula used in step 64, the flame center coordinates (x1, y1) of the first flame outline image and the flame center coordinates (x2, y2) of the second flame outline image are obtained.

[0041] Furthermore, the step 7 is specifically as follows:

[0042] Step 71: Based on the flame center coordinates (x1, y1) of the first flame outline image, a two-dimensional coordinate system is established again with the flame center coordinates as the origin, and the coordinate system is divided into two regions: 0°-180° is region 3; 180°-360° is region 4;

[0043] Step 72: Calculate the distance from the edge point of the flame outline at each angle on the first flame outline image to the center of the circle, which is the flame radius at each angle, and calculate the radius mean of all flame radii;

[0044] Step 73: using the standard deviation formula, calculate the standard deviation of the flame radius at each angle, and take the angle corresponding to the flame radius within the range of the standard deviation greater than the threshold as the range of the flame edge contour affected by the ignition electrode;

[0045] Step 74: According to the pixel width of the ignition electrode itself and the range of the flame edge contour affected by the ignition electrode, the influence range θ1 of the ignition electrode on the flame edge contour in region three and the radius mean r1 within this interval are calculated according to the inverse trigonometric function formula, and the influence range θ2 of the ignition electrode on the flame edge contour in region four and the radius mean r2 within this interval are calculated; the inverse trigonometric function formula is as follows:

[0046]

[0047] In the formula, x i and i Represents the horizontal and vertical coordinates of the flame edge contour farthest from the ignition electrode within the influence range of the ignition electrode.

[0048] Furthermore, the step 8 is specifically as follows:

[0049] Step 81: For the first flame outline image, within the region 3, the ignition electrode affects the flame edge outline within the range θ1, and with the base point as the center of the circle, the edge outline of the second flame outline image within the same range θ1 without the influence of the ignition electrode is replaced;

[0050] Step 82: replacing the edge contour of the range θ2 affected by the ignition electrode in region 4 of the first flame contour image with the flame edge contour of the second flame contour image in the same direction without the influence of the ignition electrode, with the base point as the center of the circle, to obtain a flame streak image of the flame after the influence of the ignition electrode is removed from the first flame contour image;

[0051] Step 83: Using the methods of step 81 and step 82, the edge contour of the second flame contour image affected by the ignition electrode is replaced with the flame edge contour of the first flame contour image at the same angle without the influence of the ignition electrode, so as to obtain the flame pattern image of the flame after removing the influence of the ignition electrode from the second flame contour image.

[0052] The beneficial effects of the present invention are as follows: the present invention targets the influence of the ignition electrode on the flame edge contour, uses a high-correlation edge contour to replace the area affected by the ignition electrode, and obtains a better flame edge contour. It not only more reasonably calculates the flame center and the flame propagation radius, but also provides certain theoretical support for the changing laws of the development history of the flame radius of each part. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flame pattern picture.

[0054] Figure 2 Schematic diagram of the arrangement of ignition electrodes in a constant volume incendiary bomb.

[0055] Figure 3 This is a schematic diagram of the flame overlay image area - image processing process.

[0056] Figure 4 Schematic diagram of the initial flame center obtained for a single flame schlieren image. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] The method of determining the center of the laminar flame and the flame propagation radius of the present invention is carried out under the conditions of an initial pressure of 2 bar, an initial equivalence ratio of 1.0, an initial temperature of 348 K, and a dilution rate of 10%. The specific implementation steps are as follows:

[0059] Step 1: When all initial experimental conditions such as initial temperature and initial pressure are selected, ignite the flame through the constant volume combustion bomb ignition electrode, take a flame pattern image, and obtain a flame pattern image at a certain moment, such as Figure 1 shown.

[0060] Step 2: Repeat the experiment after rotating only the ignition electrode by 90° to obtain the flame pattern image. The specific process is as follows:

[0061] Step 21: While ensuring that the conditions of the constant volume incendiary bomb body remain unchanged, only rotate the ignition electrode around the geometric center of the shooting plane, so that the position of the ignition electrode after rotation forms a 90° angle with the position of the ignition electrode under the conditions of step 1. The arrangement of the ignition electrodes in the constant volume incendiary bomb is as follows: Figure 2 shown.

[0062] Step 22: Carry out the experiment again with the initial conditions set in step 1, and take pictures of the flame pattern under these conditions.

[0063] Step 23: Select the flame pattern image obtained in step 22 and the flame pattern image at the same time as step 1.

[0064] Step 24: In addition, according to the shooting time of the flame pattern image obtained in step 23, 5 flame pattern images with the same shooting intervals before and after this shooting time are obtained.

[0065] Step 25: Summarize the flame pattern images obtained in step 23 and step 24, totaling eleven flame pattern images.

[0066] Step 3: Preprocess the flame pattern images obtained in step 1 and step 2, and obtain the edge contours of the flame pattern images of each image based on Chopin's algorithm.

[0067] Step 4: Overlay the flame pattern images obtained and preprocess the overlay images. The specific process is as follows:

[0068] Step 41: According to the size of the flame pattern shadow image, the midpoint of the two diagonal lines of the flame pattern shadow image is obtained as the geometric center of the flame pattern shadow image.

[0069] Step 42: Define the geometric center described in step 41 as the base point of the superimposed flame pattern image.

[0070] Step 43: Superimpose the Schlieren images obtained in step 1 with the Schlieren images obtained in step 2 in pairs according to the base points described in step 42.

[0071] Step 44: A two-dimensional coordinate system is established with the base point as the origin O for the eleven superimposed images obtained in step 43.

[0072] Step 45: Based on the two-dimensional coordinate system obtained in step 44, the flame region of the flame pattern image at 0°-180° is defined as region 1, and the flame region of the flame pattern image at 180°-360° is defined as region 2.

[0073] Step 5: Process and analyze the superimposed images obtained in step 4 to obtain the most ideal flame superimposed image. The specific process is as follows:

[0074] Step 51: Take the midline of any two adjacent ignition electrodes in area 1 of each superimposed image. The midline intersects the two edge contours in area 1 at pixel points A0 and B0, and the two edge contours in area 2 at pixel points C0 and D0. Figure 3 shown.

[0075] Step 52: Based on the distance formula The distances from the pixel points A0, B0 and the pixel points C0, D0 obtained in step 51 to the origin O are calculated.

[0076] Step 53: Based on the data in step 52, the percentage error between OA0 and OB0 in area 1 and the percentage error between OC0 and OD0 in area 2 are calculated according to the percentage formula.

[0077] Step 54: If the percentage errors obtained in step 53 are all less than 5%, it means that the two flame edge contours of the superimposed images are highly similar at this angle.

[0078] Step 55: Using the center line obtained in step 54 as a reference, draw 10 straight lines through the origin to both sides with a step length of 1 degree.

[0079] Step 56: Based on the operation of step 55, take the moment when the straight line intersects the two flame edge contours at the same time and record the pixel point A i (i=-10,…,-1,1,…10), B i (i=-10,…,-1,1,…10) and C i (i=-10,…,-1,1,…10), D i (i=-10,…,-1,1,…10).

[0080] Step 57: According to the calculation method of step 54, the percentage error of the length from the edge point to the origin at each angle is calculated again;

[0081] Step 58: Calculate the arithmetic mean of the percentage errors of the lengths from the edge points to the origin at all angles obtained in steps 54 and 55.

[0082] Step 59: The flame superposition image with the smallest arithmetic mean is regarded as the most ideal flame superposition image, and the first flame outline image corresponding to the original image obtained in step 1 under this condition and the second flame outline image corresponding to the original image obtained in step 2 are extracted.

[0083] Step 6: Determine the initial center of the first flame outline image and the second flame outline image. The specific process is as follows:

[0084] Step 61: Re-establish the initial two-dimensional coordinate system for the first flame outline image and the second flame outline image based on the pixel origin of the flame pattern image, such as Figure 4 shown.

[0085] Step 62: Get the maximum and minimum pixel points E1 and E2 on the ordinate of the first flame outline image and the maximum and minimum pixel points E3 and E4 on the abscissa of the flame outline edge point, and then get the positive and negative endpoints F1 and F2 of the ignition electrode.

[0086] Step 63: Draw four straight lines tangent to the edge contour through the edge maximum point, and the four straight lines intersect with the four endpoints of the matrix. Draw the two diagonals of the matrix intersecting at the geometric center G; connect the endpoints F1 and F2 of the positive and negative electrodes of the ignition electrode, and the midpoint of the line connecting the endpoints is the ignition electrode center H. Then draw a line connecting the two endpoints G and H, and the midpoint M of the line is the initial flame center.

[0087] Step 64: Draw a straight line through the initial flame center M in a clockwise direction at a fixed angle. When the straight line intersects the flame edge contour at the same time, i (i=2,3,…n) and Y i (i=2,3,…n), take the coordinates of its midpoint Q i (i=2,3,…n)=(X i +Y i ) / 2; Calculate the measurement center Q of each correction radius i The average value of the coordinates and the initial flame center M coordinates gives the initial circle center coordinates

[0088] Step 65: Based on the calculation formula used in step 64, the flame center coordinates (x1, y1) of the first flame outline image are obtained.

[0089] Step 66: Compare the flame center coordinates obtained with the superposition base point. If the error is less than 5%, it indicates superposition and the superposition base point has a high degree of credibility.

[0090] Step 67: Calculate the flame center coordinates (x2, y2) of the second flame outline image using the above method, and determine the credibility of the flame center coordinates.

[0091] Step 7: Determine the range of the flame edge contour affected by the ignition electrode and calculate the relevant data. The specific process is as follows:

[0092] Step 71: Obtain the flame center coordinates (x1, y1) of the first flame outline image according to step 65, and establish a two-dimensional coordinate system again with the flame center coordinates as the origin according to the method of step 45, and then divide the coordinate system into two areas: 0°-180° is area three; 180°-360° is area four.

[0093] Step 72: Based on the distance formula obtained in step 52, calculate the distance from the edge point of the flame outline to the center of the circle at each angle of the first flame outline image, which is the flame radius at each angle, and calculate the average radius of all flame radii.

[0094] Step 73: Using the Standard Deviation Formula The standard deviation of the flame radius at each angle is calculated, and the angle corresponding to the flame radius within the range of the threshold standard deviation is taken as the range of the flame edge contour affected by the ignition electrode.

[0095] Step 74: According to the pixel width of the ignition electrode itself and the range of the flame edge contour affected by the ignition electrode obtained in step 73, according to the inverse trigonometric function formula The influence range θ1 of the ignition electrode on the flame edge contour in area three of the first flame contour image and the radius mean r1 within this interval are calculated.

[0096] Step 75: According to the method of step 74, the influence range θ2 of the ignition electrode on the flame edge contour in area 4 of the second flame contour image and the radius mean r2 within this range are obtained.

[0097] Step 8: Replace the edge contour of the second flame contour image that is not affected by the ignition electrode with the flame contour of the first flame contour image that is affected by the ignition electrode. The specific process is as follows:

[0098] Step 81: Based on the influence range θ1 of the ignition electrode on the flame edge contour in area three of the first flame contour image obtained in step 74, in the best flame overlay image selected in step 59, with the base point as the center of the circle, use the edge contour of the second flame contour image without the influence of the ignition electrode in the same θ1 range to replace the flame edge contour of the first flame contour image affected by the ignition electrode.

[0099] Step 82: Use the method of step 81 to replace the edge contour affected by the ignition electrode in area four of the first flame contour image with the flame edge contour in the same direction of the second flame contour image that is not affected by the ignition electrode, to obtain a flame pattern image of the flame after removing the influence of the ignition electrode from the first flame contour image.

[0100] Step 83: Using the method of step 81 and step 82, the edge contour of the second flame contour image affected by the ignition electrode is replaced in the same manner with the flame edge contour of the first flame contour image not affected by the ignition electrode, and the result is Figure 2 Flame schlieren image of the flame after removing the influence of the ignition electrode.

[0101] Step 9: Based on the two flame pattern images obtained in step 8 after removing the influence of the ignition electrode, the flame center coordinates (x3, y3) and (x4, y4) of the new images calculated in steps 65 and 67 are used.

[0102] Step 10: Using the method in step 52, obtain the flame radius at various angles of two flame pattern images of the flame after removing the influence of the ignition electrode.

Claims

1. A method for calculating the center of a laminar flame and the radius of flame propagation, characterized in that: The following steps are involved: Step 1: When the initial experimental conditions are selected, ignite the flame through the constant volume combustion bomb ignition electrode, take a flame pattern image, and obtain a flame pattern image at a certain moment; Step 2: After rotating the ignition electrode by 90°, repeat the experiment to obtain a set of flame pattern images; Step 3: pre-processing the flame pattern images obtained in step 1 and step 2 to obtain edge contours of the flame pattern images of each image; Step 4: Determine the geometric center of the flame pattern image as the base point, and superimpose the flame pattern image obtained in step 1 with the flame pattern image obtained in step 2 at the base point in pairs; Step 5: Process and analyze the obtained superimposed images respectively, determine the most ideal flame superimposed image based on the minimum percentage error of the length from the edge point on the midline to the origin, and extract the first flame outline image and the second flame outline image from the most ideal flame superimposed image; Step 6: Determine the initial center of the flame edge contour in the first flame contour image and the second flame contour image respectively; Step 7: Determine the range of the flame edge contour affected by the ignition electrode and calculate the relevant data; Step 8: replace the flame outline of the first flame outline image affected by the ignition electrode with the edge outline of the second flame outline image without the influence of the ignition electrode; replace the flame outline of the second flame outline image affected by the ignition electrode with the edge outline of the first flame outline image without the influence of the ignition electrode; obtain two flame schlieren images of the flame after removing the influence of the ignition electrode; Step 9: Calculate the center coordinates of the flame in two flame pattern images after removing the influence of the ignition electrode; Step 10: Calculate the flame radius at each angle of the two flame schlieren images after removing the influence of the ignition electrode; The step 7 is specifically as follows: Step 71: Based on the flame center coordinates (x1, y1) of the first flame outline image, a two-dimensional coordinate system is established again with the flame center coordinates as the origin, and the coordinate system is divided into two regions: 0°-180° is region 3; 180°-360° is region 4; Step 72: Calculate the distance from the edge point of the flame outline at each angle on the first flame outline image to the center of the circle, which is the flame radius at each angle, and calculate the radius mean of all flame radii; Step 73: using the standard deviation formula, calculate the standard deviation of the flame radius at each angle, and take the angle corresponding to the flame radius within the range of the standard deviation greater than the threshold as the range of the flame edge contour affected by the ignition electrode; Step 74: According to the pixel width of the ignition electrode itself and the range of the flame edge contour affected by the ignition electrode, the influence range θ1 of the ignition electrode on the flame edge contour in region three and the radius mean r1 within this range are calculated according to the inverse trigonometric function formula, and the influence range θ2 of the ignition electrode on the flame edge contour in region four and the radius mean r2 within this range are calculated; the trigonometric function formula is as follows: In the formula, x i and i Indicates the horizontal and vertical coordinates of the flame edge contour farthest from the ignition electrode within the influence range of the ignition electrode; The step 8 is specifically as follows: Step 81: For the first flame outline image, within the region 3, the ignition electrode affects the flame edge outline within the range θ1, and with the base point as the center of the circle, the edge outline of the second flame outline image within the same range θ1 without the influence of the ignition electrode is replaced; Step 82: replacing the edge contour of the range θ2 affected by the ignition electrode in region 4 of the first flame contour image with the flame edge contour of the second flame contour image in the same direction without the influence of the ignition electrode, with the base point as the center of the circle, to obtain a flame streak image of the flame after the influence of the ignition electrode is removed from the first flame contour image; Step 83: Using the methods of step 81 and step 82, the edge contour of the second flame contour image affected by the ignition electrode is replaced with the flame edge contour of the first flame contour image at the same angle without the influence of the ignition electrode, so as to obtain the flame pattern image of the flame after removing the influence of the ignition electrode from the second flame contour image.

2. The method for calculating the laminar flame center and flame propagation radius according to claim 1, characterized in that: The step 2 is specifically as follows: Step 21: While ensuring that the conditions of the constant volume incendiary bomb body remain unchanged, only the ignition electrode is rotated around the geometric center of the shooting plane, so that the position of the ignition electrode after rotation forms an angle of 90° with the position of the ignition electrode under the conditions of step 1; Step 22: Perform the experiment again using the initial experimental conditions set in step 1, and take a flame pattern image under this condition; Step 23: Select the flame schlieren picture obtained in step 22 at the same time as step 1; Step 24: according to the shooting time of the flame pattern image obtained in step 23, obtain N flame pattern images with the same shooting interval before and after the shooting time, N = 1, 2, 3...; Step 25: Summarize the flame pattern images obtained in step 23 and step 24, totaling 2*N+1 flame pattern images.

3. The method for calculating the laminar flame center and flame propagation radius according to claim 1, characterized in that: The geometric center of the flame pattern image is determined in step 4 as follows: according to the pixel size of the flame pattern image, the four endpoints at the upper, lower, left and right boundaries of the flame pattern image are obtained, and the intersection of the two diagonal lines formed by connecting the four endpoints is taken as the geometric center of the flame pattern image.

4. The method for calculating the laminar flame center and flame propagation radius according to claim 1, characterized in that: The step 5 is specifically as follows: Step 51: Based on the two-dimensional coordinate system, define the flame region of the flame pattern image at 0°-180° as region 1, and define the flame region of the flame pattern image at 180°-360° as region 2; Step 52: Take the midline of the angle formed by any adjacent ignition electrodes in region 1 of each superimposed image, the midline intersecting the two edge contours in region 1 at pixel points A0 and B0, and the two edge contours in region 2 at pixel points C0 and D0; Step 53: Calculate the distances from the pixel points A0, B0 and the pixel points C0, D0 to the origin O respectively; Step 54: Calculate the percentage error of the lengths of OA0 and OB0 in area 1 and the percentage error of the lengths of OC0 and OD0 in area 2 according to the percentage formula; Step 55: Taking the center line as a reference, draw 10 straight lines in clockwise and counterclockwise directions through the origin O with a step length of 1 degree; Step 56: Take the moment when the straight line intersects the two flame edge contours at the same time and record the pixel point A m , B m With C m , D m , m=-10,…,-1,1,…10; Step 57: Calculate the percentage error of the length from the edge pixel point to the origin O at each angle in step 56; Step 58: Calculate the arithmetic mean of the percentage errors of the lengths from the edge points to the origin at all angles obtained in step 54 and step 57; and take the flame superposition image with the smallest arithmetic mean as the most ideal flame superposition image.

5. The method for calculating the laminar flame center and flame propagation radius according to claim 1, characterized in that: The step 6 is specifically as follows: Step 61: re-establishing an initial two-dimensional coordinate system for the first flame outline image and the second flame outline image based on the pixel origin of the flame schlieren image; Step 62: obtaining the maximum and minimum pixel points E1 and E2 on the ordinate of the first flame outline image, and the maximum and minimum pixel points E3 and E4 on the abscissa, and then obtaining the endpoints F1 and F2 of the positive and negative electrodes of the ignition electrode; Step 63: draw four straight lines tangent to the edge contour through the edge maximum point, the four straight lines intersect with the four endpoints of the matrix, and draw two diagonals of the matrix intersecting at the geometric center G; connect the endpoints F1 and F2 of the positive and negative electrodes of the ignition electrode, the midpoint of the line connecting the endpoints is the ignition electrode center H, and then draw a line connecting the two end points G and H, the midpoint M of the line is the initial flame center; Step 64: Draw a straight line through the initial flame center M in a clockwise direction at a fixed angle. When the straight line intersects the flame edge contour at the same time, i With Y i When the coordinates of its midpoint are i =(X i +Y i ) / 2; Calculate each correction radius measurement center Q i The average value of the coordinates of the initial flame center M and the initial circle center coordinates (x0, y0) is obtained: In the formula, n represents the number of straight lines drawn with a fixed angle as the step length; Step 65: Based on the calculation formula used in step 64, the flame center coordinates (x1, y1) of the first flame outline image and the flame center coordinates (x2, y2) of the second flame outline image are obtained.

Images