A compensation method for missing points in the contour of a laminar flame image

Abstract

The present invention relates to the technical field of laminar combustion, and specifically discloses a method for compensating missing points in the contour of a laminar flame picture. The edge contour points of the flame at different moments, as well as the flame center and the flame radius at each angle, are obtained by processing the experimentally obtained flame schlieren pictures. A two-dimensional coordinate system is established with the flame center as the origin. The influence range of the ignition electrode is preliminarily determined, and the red data points near the area affected by the ignition electrode are fitted to fill the vacancies. The vacancies in the area of the red data points within the area not affected by the ignition electrode are filled. The unreliable data points in the summary flame radius change trend graph are removed. After filling the data points excluding the ignition electrode and the missing data points in the flame picture contour, the edge data points on the flame edge contour map are correspondingly filled to obtain the flame picture in an ideal state. The present invention can more precisely define the influence range of the ignition electrode on the flame contour and can more precisely eliminate the influence of the ignition electrode and the flame thickness on the flame contour.

Description

Technical Field

[0001] The present invention relates to the technical field of laminar combustion, and particularly to a method for compensating missing points in the contour of a laminar flame picture. Background Art

[0002] Studying the compensation for missing contour points of laminar flame pictures is the basis for improving the accuracy of flame radius. The study of flame radius is also the basis for studying laminar combustion characteristics and numerical calculations of fuel combustion, and further has a beneficial impact on subsequent research and description of the characteristics of premixed turbulent flames. Since the study of laminar flame radius plays an important role in subsequent improvement of the fuel combustion condition and combustion efficiency of internal combustion engines, the research on compensating missing points in the contour of laminar flame pictures provides strong data support for subsequent in-depth study of laminar combustion characteristics. With the development of visualization technology, the overall demand for constant volume combustion experimental systems and the demand for the processing accuracy of laminar flame pictures are increasing day by day.

[0003] In recent years, through the analysis of a large number of flame propagation pictures under different working conditions by many scholars, it has been confirmed that the ignition electrode is the most influential factor on laminar flame propagation in its direction. At the same time, due to the imperfect flame contour edge detection technology, some edge contour points cannot be effectively identified due to the influence of the flame thickness in the flame propagation picture. So far, although some scholars have proposed some rough optimization schemes to remove the ignition electrode to reduce its influence, so far, the proposed schemes have not been able to compensate for the missing points in the flame picture contour from the perspective of the missing points in the flame picture contour, using relevant picture processing methods to eliminate the influence of the ignition electrode and flame thickness on the flame contour and the adaptability problem of flame contour changes under different working conditions. In order to reduce the influence of the ignition electrode on the flame boundary contour and reduce the calculation error of the flame radius, this method is proposed. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a method for compensating missing points in the contour of a laminar flame picture, so as to more effectively eliminate the influence of the ignition electrode and flame thickness on the flame edge contour and the influence of the missing points in the flame picture contour on the flame radius, thereby providing theoretical and algorithm support for obtaining a more accurate flame radius; and it is beneficial to obtain higher-precision laminar flame combustion characteristics based on subsequent data analysis of the laminar flame radius, and further provide data support for the research of turbulent flame characteristics. The technical solution is as follows:

[0005] A method for compensating missing points in the contour of a laminar flame picture includes the following steps:

[0006] Step 1: Preprocess the flame schlieren picture obtained from an experiment under a certain initial condition to obtain flame contour maps at different times;

[0007] Step 2: According to the flame contour map, obtain the flame edge contour points at different moments, as well as the flame center (x0, y0) and the flame radius R at each angle at the corresponding moment. i ;

[0008] Step 3: Take the flame center (x0, y0) as the origin, and take the negative half-axis angle of the abscissa as 0°, and establish a two-dimensional coordinate system.

[0009] Step 4: Draw a two-dimensional trend graph of the flame radius changing with the angle, mark the flame radius data points at the angles that have a greater impact on the change of the flame radius in the entire interval in red, and initially determine its influence range as the ignition electrode.

[0010] Step 5: Conduct preliminary processing on the trend graph of the flame radius changing with the angle.

[0011] Step 6: Fit the red data points near the area affected by the ignition electrode and fill in the vacancies.

[0012] Step 7: Operate on the trend graph of the flame radius changing with the angle at the remaining moments according to the method in Step 6, and summarize the results to obtain a summarized trend graph of the flame radius change in which all the vacancies in the area affected by the ignition electrode are filled.

[0013] Step 8: Fill in the vacancies in the area of the red data points in the area not affected by the ignition electrode.

[0014] Step 9: Remove the unreliable data points in the summarized trend graph of the flame radius change.

[0015] Step 10: Remove the unreliable data points removed in Step 9 from the summarized trend graph of the flame radius change that has been filled.

[0016] Step 11: After filling in the data points excluding the ignition electrode and the data points with missing flame picture contours, according to the existing flame center and the compensated flame radius at each angle, perform corresponding filling on the edge data points on the flame edge contour map.

[0017] Step 12: According to the obtained complete flame edge contour picture, determine that the complete flame edge contour picture is the flame picture in the ideal state.

[0018] Further, the specific content of initially determining the influence range of the ignition electrode in Step 4 includes:

[0019] Step 41: According to the flame radius R i , calculate the standard deviation σ0 of the flame radius at each angle in the entire interval relative to the mean value of the flame radius in the entire interval through the following standard deviation formula.

[0020]

[0021] In the formula, x i is the flame radius at the i-th angle; μ is the average value of the flame radius in the whole interval; n is the maximum number of digits of the number of flame radii in the interval; N is the number of samples of the flame radius in the whole interval;

[0022] Step 42: Starting from 0° to 360°, calculate the standard deviation σ of the flame radius at each angle relative to the mean value of the flame radii at all other angles i , i = 1, 2, 3, … n;

[0023] Step 43: Based on the obtained standard deviation σ i , compare the influence of the flame radius at each angle on the change of the flame radius in the whole interval; if σ i < σ0, it indicates that the flame radius at this angle has a greater influence on the change of the flame radius in the whole interval;

[0024] Step 44: Summarize the flame radii at each angle at a certain moment, and draw a two-dimensional trend chart of the flame radius changing with the angle;

[0025] Step 45: Summarize the flame radii that satisfy the condition of σ i < σ0 under 0° - 360°, and mark the summarized flame radius data points as red in the above-mentioned trend chart of the flame radius changing with the angle;

[0026] Step 46: Initially determine that the range of the red flame radius data points near the ignition electrode is the influence range of the ignition electrode on the flame profile.

[0027] Furthermore, the specific content of step 5 is as follows:

[0028] Step 51: Based on the trend chart of the flame radius changing with the angle marked with red data, divide the trend chart into four regions: 0° - 90° is the first region, 90° - 180° is the second region, 180° - 270° is the third region, and 270° - 360° is the fourth region;

[0029] Step 52: Identify the region of the red data points near 90° in the trend chart of the flame radius changing with the angle as the region where the upper half of the picture is affected by the ignition electrode, and identify the region of the red data points near 270° in the trend chart of the flame radius changing with the angle as the region where the lower half of the picture is affected by the ignition electrode.

[0030] Furthermore, the specific content of step 6 is as follows:

[0031] Step 61: Based on the division of the red data points on the flame radius change trend graph in Step 52, extract the m red data points closest to 90° within the area of the upper half picture affected by the ignition electrode, where m = 1, 2, 3, …;

[0032] Step 62: Use the polyfit function based on MATLAB software to perform polynomial fitting on the m red data points to obtain the corresponding polynomial equation;

[0033] Step 63: Extract the vacant angles without data points within the area of the m red data points;

[0034] Step 64: According to the polynomial equation obtained in Step 62, use the polyval function of MATLAB software to obtain the function values of the polynomial at the vacant angles without data points within the area of the red data points;

[0035] Step 65: Add the function values at the vacant angles obtained in Step 64 to the flame radius data to ensure that there are corresponding data points at all angles within the area of the red data points;

[0036] Step 66: Use the above method to fill in the data points for the vacant angles without data points within the area of the n red data points closest to 270° in the area of the lower half picture affected by the ignition electrode, and supplement the data points to the flame radius change trend graph with respect to the angle.

[0037] Furthermore, the specific content of Step 7 is as follows:

[0038] Step 71: On the basis of the method in Step 6, fill in the vacancies in the area affected by the ignition electrode in the flame radius change trend graph obtained at each moment in the same way;

[0039] Step 72: Summarize the flame radius change trend graphs obtained at each moment in Step 71 to obtain a summarized flame radius change trend graph in which all the vacancies in the area affected by the ignition electrode are filled.

[0040] Furthermore, the specific content of Step 8 is as follows:

[0041] Step 81: According to the division in Step 51, perform fitting on the red data points near the intersection of Region 1 and Region 4, that is, near 0° or 360°, according to the method in Step 6;

[0042] Step 82: Calculate the function values for the vacancies without data points within the area of the red data points of the original curve according to the polynomial fitting function, and fill the obtained data points into the original flame radius change trend graph;

[0043] Step 83: Fill in the vacant data points in the red data point area near the intersection of the second and third regions, i.e., within the range of 180°, according to the method in Step 82;

[0044] Step 84: Compensate the vacant data points within the range of the red data points near 0° and 180° in the trend graph of the flame radius changing with the angle at other times according to the above method;

[0045] Step 85: Add all the data points obtained in the above steps to the compensated summary trend graph of the flame radius change.

[0046] Furthermore, the specific content of Step 9 is as follows:

[0047] Step 91: According to the summary trend graph of the flame radius change obtained in Step 7, obtain the continuous vacant angle range closest to the ignition electrode within the red data point area of the upper half picture affected by the ignition electrode at each moment;

[0048] Step 92: Define the range of the vacant angle in the summary trend graph of the flame radius change at each moment in the area of the upper half picture affected by the ignition electrode as the gap spacing k i , i = 1, 2, 3,... n;

[0049] Step 93: For the summary trend graph of the flame radius change with all the vacant angle data points filled in obtained in Step 72, cut the compensated summary trend graph of the flame radius change at the same position at each moment according to the maximum gap spacing k max obtained in the area of the upper half picture affected by the ignition electrode in Step 92, to obtain the summary trend graph of the flame radius change after cutting with the maximum gap distance;

[0050] Step 94: According to the method in Step 93, and according to the other gap spacings k i obtained in the area of the upper half picture affected by the ignition electrode in Step 92, cut the filled summary trend graph of the flame radius change at the same position to obtain the summary trend graph of the flame radius change after cutting with the minimum gap distance;

[0051] Step 95: Calculate the overall standard deviation σ n of the summary trend graphs of the flame radius change after cutting with each gap distance obtained in Step 93 and Step 94 according to the standard deviation formula used in Step 41;

[0052] Step 96: According to the overall standard deviation σ n of the summary trend graphs of the flame radius change after cutting with each gap distance obtained in Step 95, select the optimal cutting gap spacing k a with the minimum overall standard deviation as the target cutting angle;

[0053] Step 97: Similarly, select the optimal excision gap distance k of the region of the lower half image affected by the ignition electrode. b ;

[0054] Step 98: Define that all data points existing within the optimal excision gap distance are untrusted data points.

[0055] Step 99: According to the optimal excision gap distances selected in Step 96 and Step 97, excise the untrusted data points in the regions of the upper half image and the lower half image affected by the ignition electrode in the aggregated flame radius change trend graph.

[0056] The beneficial effects of the present invention are as follows:

[0057] (1) The present invention can more precisely define the influence range of the ignition electrode on the flame contour.

[0058] (2) The present invention provides a method for eliminating the influence of the ignition electrode on the flame contour, which can more precisely eliminate the influence of the ignition electrode on the flame contour.

[0059] (3) The present invention proposes an optimization method for the flame radius. The method is simple and has good adaptability. It can adapt to schlieren images under different working conditions and is closer to the theoretical flame propagation situation.

[0060] (4) The optimized flame radius at each angle of the present invention provides better data support for subsequent laminar combustion characteristics research and turbulent combustion research. Brief Description of the Drawings

[0061] Figure 1 It is a graph of the change trend of the flame radius at each angle at different times.

[0062] Figure 2 It is a graph of the change trend of the flame radius at each angle at different times after calculating the red data points.

[0063] Figure 3 It is a graph of the change trend of the flame radius at each angle at different times after compensating for the missing contour.

[0064] Figure 4 It is a graph of the change trend of the flame radius after optimizing the influence of the ignition electrode and the influence of the missing contour points. Detailed Embodiment

[0065] The following further describes the present invention in detail with reference to the drawings and specific embodiments. The present invention discloses a method for compensating for missing contour points in laminar flame images, including the following steps:

[0066] Step 1: Preprocess the flame schlieren image obtained from an experiment under a certain initial condition to obtain the flame contour images at different times.

[0067] Step 2: According to the existing method for processing schlieren images of flames, obtain the flame edge contour points at different moments, as well as the flame center (x0, y0) and the flame radius R at each angle at the corresponding moment. i 。

[0068] Step 3: Taking the flame center obtained in Step 2 as the origin, and taking the negative semi-axis of the abscissa as 0°, establish a two-dimensional coordinate system.

[0069] Step 4: Initially determine the influence range of the ignition electrode:

[0070] Step 41: According to the flame radius data obtained in Step 2, use the standard deviation formula to obtain the standard deviation σ0 of the flame radius at each angle in the entire interval relative to the mean value of the flame radius in the entire interval.

[0071] Step 42: Using the calculation method in Step 41, starting from 0° to 360°, calculate the standard deviation σ of the flame radius at each angle relative to the mean value of the flame radii at all other angles. i (i = 1, 2, 3, … n).

[0072] Step 43: Based on the standard deviation σ obtained in Step 42, compare the influence of the flame radius at each angle on the change of the flame radius in the entire interval. i On this basis, compare the influence of the flame radius at each angle on the change of the flame radius in the entire interval.

[0073] Step 44: According to the method in Step 43, observe the influence of the flame radius at each angle on the change of the flame radius in the entire interval. If σ i < σ0, it indicates that the flame radius at this angle has a greater influence on the change of the flame radius in the entire interval.

[0074] Step 45: Summarize the flame radii at each angle obtained in Step 2 at a certain moment, and draw a two-dimensional trend diagram of the flame radius changing with the angle; the trend diagrams of the flame radii at each angle at different moments are as Figure 1 shown.

[0075] Step 46: Summarize the flame radii that satisfy the condition of σ i < σ0 under 0° - 360°.

[0076] Step 47: Mark the data points of the flame radii that meet the conditions as red in the trend diagram of the flame radius changing with the angle obtained in Step 45.

[0077] Step 48: Initially determine that the range of the red flame radius data points near the ignition electrode is the influence range of the ignition electrode on the flame contour.

[0078] The change trend diagram of the flame radius at each angle at different times after calculating the red data points is as follows Figure 2 shown

[0079] Step 5: Conduct preliminary processing on the change trend diagram of the flame radius with respect to the angle;

[0080] Step 51: Based on the change trend diagram of the flame radius obtained in Step 47, divide the trend diagram into four regions: 0° - 90° is the first region, 90° - 180° is the second region, 180° - 270° is the third region, and 270° - 360° is the fourth region;

[0081] Step 52: According to the definition in Step 48, identify the region of the red data points near 90° in the change trend diagram of the flame radius with respect to the angle as the region in the upper half picture affected by the ignition electrode, and identify the region of the red data points near 270° in the change trend diagram of the flame radius with respect to the angle as the region in the lower half picture affected by the ignition electrode.

[0082] Step 6: Fit the red data points near the region affected by the ignition electrode and fill in the vacancies;

[0083] Step 61: Based on the division of the red data points on the change trend diagram of the flame radius in Step 52, extract the m (m = 1, 2, 3,...) red data points closest to 90° in the region in the upper half picture affected by the ignition electrode;

[0084] Step 62: Use the polyfit function based on the MATLAB software to perform polynomial fitting on the m data points obtained in Step 61 to obtain the corresponding polynomial equation;

[0085] Step 63: Extract the vacant angles where there are no data points in the region of the red data points obtained in Step 61;

[0086] Step 64: According to the polynomial equation obtained in Step 62, use the polyval function of the MATLAB software to obtain the function values of the polynomial at the vacant angles where there are no data points in the region of the red data points;

[0087] Step 65: Add the function values corresponding to the vacant angles obtained in Step 64 to the flame radius data to ensure that there are corresponding data points at all angles in the region of the red data points;

[0088] Step 66: Use the above method to fill in the data points for the vacant angles where there are no data points in the region of the n red data points closest to 270° in the region in the lower half picture affected by the ignition electrode, and supplement the data points to the change trend diagram of the flame radius with respect to the angle.

[0089] Step 7: Operate on the flame radius vs. angle trend graphs for the remaining moments according to the method in Step 6, and summarize the results;

[0090] Step 71: On the basis of the method in Step 6, under the conditions of this experiment, fill the vacancies in the regions affected by the ignition electrode in the flame radius vs. angle trend graphs obtained at each moment in the same way;

[0091] Step 72: Summarize the flame radius change trend graphs obtained at each moment in Step 71 to obtain a summarized flame radius change trend graph in which all the vacancies in the regions affected by the ignition electrode are filled.

[0092] The flame radius change trend graphs at different moments after compensating for the missing profiles are as Figure 3 shown.

[0093] Step 8: Fill in the vacancies in the red data point regions within the regions not affected by the ignition electrode;

[0094] Step 81: According to the division in Step 51, fit the red data points near the intersection of Region 1 and Region 4, i.e., near 0° or 360°, according to the method in Step 6;

[0095] Step 82: Calculate the function values for the vacancies without data points in the red data point regions of the original curve according to the polynomial fitting function and fill the obtained data points into the original flame radius change trend graph;

[0096] Step 83: According to the method in Step 82, fill the vacancy data points in the red data point regions near the intersection of Region 2 and Region 3, i.e., near 180°;

[0097] Step 84: According to the above method, compensate for the vacancy data points within the range of the red data points near 0° and 180° in the flame radius vs. angle trend graphs for the remaining moments;

[0098] Step 85: Add all the data points obtained in the above steps to the compensated summarized flame radius change trend graph.

[0099] Step 9: Process the unreliable data points in the summarized flame radius change trend graph:

[0100] Step 91: According to the summarized flame radius change trend graph obtained in Step 7, obtain the continuous vacancy angle range closest to the ignition electrode in the red data point regions in the upper half of the picture affected by the ignition electrode at each moment;

[0101] Step 92: Define the range of the vacancy angles in the upper half of the picture affected by the ignition electrode in the summarized flame radius change trend graph at each moment as the gap spacing k i(i = 1, 2, 3, … n);

[0102] Step 93: For the summarized flame radius change trend graph in which the vacant angle data points obtained in Step 72 are all filled, according to the maximum gap distance k obtained in the ignition electrode affected area of the upper half picture in Step 92 max , cut the summarized flame radius change trend graph after filling the vacant angle data points at the same position at each moment to obtain the summarized flame radius change trend graph after cutting the maximum gap distance;

[0103] Step 94: According to the method in Step 93, according to the remaining gap distances k obtained in the ignition electrode affected area of the upper half picture in Step 92 i , cut the filled summarized flame radius change trend graph at the same position to obtain the summarized flame radius change trend graph after cutting the minimum gap distance;

[0104] Step 95: According to the standard deviation formula used in Step 41, calculate the overall standard deviation σ of the summarized flame radius change trend graphs after cutting at each gap distance obtained in Step 93 and Step 94 n ;

[0105] Step 96: According to the overall standard deviation σ after cutting at each gap distance obtained in Step 95 n , take the optimal cutting gap distance k under the minimum overall standard deviation a as the target cutting angle;

[0106] Step 97: Use the above steps to select the optimal cutting gap distance k in the ignition electrode affected area of the lower half picture b ;

[0107] Step 98: Define that all data points existing within the optimal cutting gap distance are untrustworthy data points;

[0108] Step 99: According to the optimal cutting gap distances selected in Step 96 and Step 97, cut the untrustworthy data points in the ignition electrode affected area of the upper half picture and the ignition electrode affected area of the lower half picture of the summarized flame radius change trend graph.

[0109] Step 10: Remove the untrustworthy data points cut in Step 9 from the filled summarized flame radius change trend graph.

[0110] Step 11: After filling the data points excluding the ignition electrode and the data points with missing flame picture contours, according to the existing flame center and the flame radius at each compensated angle, fill the corresponding edge data points on the flame edge contour graph.

[0111] Step 12: Based on the supplemented and complete flame edge contour picture obtained in Step 11, it can be determined that the supplemented and complete flame edge contour picture is the flame picture in the ideal state.

[0112] The changing trend diagram of the flame radius after optimizing the influence of the ignition electrode and the influence of the missing contour points is as Figure 4 shown.

Claims

1. A compensation method for missing points in the contour of a laminar flame image, characterized in that, It includes the following steps: Step 1: Preprocess the flame schlieren images obtained from experiments under a certain initial condition to obtain the flame contour maps at different times; Step 2: According to the flame contour diagram, obtain the flame edge contour points at different moments, as well as the flame center (x0, y0) and the flame radius R at each angle at the corresponding moment i ; Step 3: Taking the center of the flame (x0, y0) as the origin, and taking the angle of the negative half-axis of the abscissa as 0°, establish a two-dimensional coordinate system; Step 4: Plot a two-dimensional trend graph of the flame radius varying with the angle, and calculate the standard deviation σ of the flame radius at each angle within the entire interval with respect to the mean value of the flame radii at all other angles i Mark the data points of the flame radius with a standard deviation σ less than the standard deviation σ0 of the flame radius with respect to the mean value of the flame radius within the entire interval in red, and preliminarily determine its influence range as the ignition electrode Step 5: Conduct preliminary processing on the trend graph of the flame radius changing with the angle; Step 6: Fit and fill the vacant positions of the red data points near the area affected by the ignition electrode; Step 7: Operate on the trend graph of the flame radius changing with the angle at the remaining times according to the method in Step 6, and summarize the results to obtain a summarized trend graph of the flame radius change in which all the vacant positions within the area affected by the ignition electrode are filled; Step 8: Fill in the vacant positions in the area of the red data points within the area not affected by the ignition electrode; Step 9: Remove the untrustworthy data points in the summarized trend graph of the flame radius change; Step 10: Remove the untrustworthy data points removed in Step 9 from the summarized trend graph of the flame radius change that has been filled; Step 11: After filling in the data points excluding the ignition electrode and the data points with missing flame picture contours, according to the existing center of the flame and the flame radius at each compensated angle, perform corresponding filling on the edge data points on the flame edge contour graph; Step 12: According to the obtained complete flame edge contour picture, recognize the complete flame edge contour picture as the flame picture in the ideal state; The specific content of Step 4 for preliminarily determining the influence range of the ignition electrode includes: Step 41: According to the flame radius R i , calculate the standard deviation σ0 of the flame radius at each angle in the entire range relative to the mean value of the flame radius in the entire range through the following formula; where x i is the flame radius at the i-th angle; μ is the average value of the flame radius over the entire interval; n is the maximum number of digits of the number of flame radii within the interval; Step 42: Starting from 0° and ending at 360°, calculate the standard deviation σ of the flame radius at each angle relative to the mean value of the flame radii at all other angles i , where i = 1, 2, 3, … n; Step 43: Based on the obtained standard deviation σ i , compare the influence of the flame radius at each angle on the change of the flame radius within the entire range; if σ i < σ0, it indicates that the flame radius at this angle has a greater influence on the change of the flame radius within the entire range; Step 44: Summarize the flame radii at each angle at a certain moment, and draw a two-dimensional trend graph of the flame radius changing with the angle; Step 45: Aggregate the flame radii that satisfy the condition of σ i < σ0 at 0° - 360°, and mark the aggregated flame radius data points as red in the above-mentioned trend graph of the flame radius varying with the angle;​​ Step 46: Preliminarily recognize the range of the red flame radius data points near the ignition electrode as the influence range of the ignition electrode on the flame contour; The specific content of Step 5 is as follows: Step 51: On the basis of the trend graph of the flame radius changing with the angle marked with red data, divide the trend graph into four regions: 0° - 90° is one region, 90° - 180° is the second region, 180° - 270° is the third region, and 270° - 360° is the fourth region; Step 52: Recognize the region of the red data points near 90° in the trend graph of the flame radius changing with the angle as the region in the upper half picture affected by the ignition electrode, and recognize the region of the red data points near 270° in the trend graph of the flame radius changing with the angle as the region in the lower half picture affected by the ignition electrode; The specific content of Step 9 is as follows: Step 91: According to the summarized trend graph of the flame radius change obtained in Step 7, obtain the continuous vacant position angle range closest to the ignition electrode within the region of the red data points in the area affected by the ignition electrode in the upper half picture at each moment; Step 92: Define that the range of the vacancy angle of the area affected by the ignition electrode in the upper half picture of the summary flame radius change trend graph at each moment is the gap spacing k i , i = 1, 2, 3, … n; Step 93: For the summarized flame radius change trend diagram in which the vacant position angle data points obtained in Step 72 are all filled, according to the maximum gap spacing k obtained in the area affected by the ignition electrode in the upper half of the picture in Step 92 max , cut the summarized flame radius change trend diagram after filling the vacant position angle data points at the same position at each moment to obtain the summarized flame radius change trend diagram after cutting the maximum gap distance; Step 94: According to the method in Step 93, and based on the remaining gap spacing k obtained in the area of the upper half picture affected by the ignition electrode in Step 92, i excise the filled summary flame radius change trend graph at the same position to obtain the summary flame radius change trend graph after excising the minimum gap distance; Step 95: Calculate the overall standard deviation σ of the summarized flame radius change trend chart after removing each gap distance obtained in Steps 93 and 94 according to the standard deviation formula used in Step 41 n for calculation; Step 96: Cut the overall standard deviation σ obtained in Step 95 according to the respective gap distances n , and take the optimal cutting gap spacing k under the minimum overall standard deviation a as the target cutting angle; Step 97: Similarly, select the optimal cutting gap spacing k of the area of the lower half picture affected by the ignition electrode b ; Step 98: Define that all the data points existing within the optimal excision gap spacing are untrustworthy data points; Step 99: According to the optimal excision gap spacing selected in Step 96 and Step 97, remove the untrustworthy data points in the area affected by the ignition electrode in the upper half picture and the area affected by the ignition electrode in the lower half picture of the summarized trend graph of the flame radius change.

2. The compensation method for the missing points of the laminar flame picture contour according to claim 1, characterized in that, The specific content of Step 6 is as follows: Step 61: Based on the division of the red data points on the graph of the variation trend of the flame radius with the angle in Step 52, extract the m red data points closest to 90° within the region of the upper half picture affected by the ignition electrode, where m = 1, 2, 3, …; Step 62: Use the polyfit function based on the MATLAB software to perform polynomial fitting on the m red data points; Obtain the corresponding polynomial equation; Step 63: Extract the vacant angles where there are no data points within the region of the m red data points; Step 64: According to the polynomial equation obtained in Step 62, use the polyval function of the MATLAB software to obtain the function values of the polynomial at the vacant angles where there are no data points within the region of the red data points; Step 65: Add the function values at the vacant angles obtained in Step 64 to the flame radius data to ensure that there are corresponding data points at all angles within the region of the red data points; Step 66: Use the above method to fill in the data points for the vacant angles where there are no data points within the region of the n red data points closest to 270° within the region of the lower half picture affected by the ignition electrode, and supplement the data points to the graph of the variation trend of the flame radius with the angle.

3. The compensation method for the missing points of the laminar flame picture contour according to claim 2, characterized in that, The specific content of Step 8 is as follows: Step 81: Based on the division in Step 51, perform fitting on the red data points near the intersection of Region 1 and Region 4, i.e., near 0° or 360°, according to the method in Step 6; Step 82: Calculate the function values for the vacant positions where there are no data points within the region of the red data points of the original curve according to the polynomial fitting function, and fill the obtained data points into the original graph of the variation trend of the flame radius with the angle; Step 83: According to the method in Step 82, fill in the vacant data points within the region of the red data points near 180°, i.e., at the intersection of Region 2 and Region 3; Step 84: According to the above method, compensate for the vacant data points within the range of the red data points near 0° and 180° in the graph of the variation trend of the flame radius with the angle at other moments; Step 85: Add all the data points obtained in the above steps to the compensated summary graph of the variation trend of the flame radius.

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