A method for determining the range of the unreliable radius of a flame

Abstract

The present invention discloses a method for determining the unreliable radius range of a flame. The schlieren image of the flame propagation radius to be calculated is preprocessed to obtain the flame edge contour map; then the measurement center of the flame propagation radius is determined, and then the ratio between the size of the captured image and the corresponding pixel value in the schlieren image is calculated; the unreliable radius range affected by the ignition electrode is determined, and finally, by comparing the radius difference with the accuracy error standard of the radius difference change diagram, the angular range corresponding to the part of the radius difference exceeding the accuracy error standard of the radius difference change diagram is the unreliable radius range of the corresponding area. The present invention can analyze the influence degree of the ignition electrode on each part, so as to determine the unreliable range of the flame radius; it is not only convenient for calculating the flame radius more reasonably, but also can distinguish the influence of the ignition electrode on the four regions, providing certain theoretical support for the change law of the development process of the flame radius of each part.

Description

Technical Field

[0001] The invention relates to the technical field of laminar combustion, in particular to a method for determining an untrustworthy radius range of a flame. Background Art

[0002] Studying the laminar combustion characteristics is a necessary process to understand the fuel combustion process, improve combustion efficiency and develop efficient and clean combustion control strategies. It is the basis for describing the characteristics of turbulent flames. In recent years, in order to further study the laminar combustion characteristics, some scholars have begun to use constant volume combustion bombs to obtain the instantaneous radius of laminar flames at different times, so as to study the laws of laminar combustion characteristic parameters. However, there is uneven propagation of laminar combustion flames, so the degree of optimization of the laminar combustion flame radius calculation method directly affects the accuracy of laminar combustion characteristic parameters, which is particularly important for the study of the regularity of laminar combustion rate. There are many factors that lead to uneven flame propagation, mainly floating, deformation, floating and deformation. Based on the various deformation conditions of the spherical expansion flame schlieren diagram studied by constant volume combustion bombs, scholars have analyzed and confirmed that the existence of the ignition electrode is one of the main reasons for the distortion of the flame propagation radius in this direction. An optimization method for measuring the flame radius is also proposed, but this type of measurement method does not take into account the weight of the influence of the ignition electrode on each part, nor does it take into account the adaptability of the radius accuracy error to the laminar combustion flame propagation speed. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a method that can analyze the influence of the ignition electrode on each part, so as to determine the unreliable range of the flame radius. Not only can the flame radius be calculated more reasonably, but also the influence of the ignition electrode on the four areas can be distinguished, and a certain theoretical support is provided for the change law of the development process of the flame radius of each part. The technical solution is as follows:

[0004] A method for determining a flame untrustworthy radius range comprises the following steps:

[0005] Step 1: Preprocess the Schlieren image of the flame propagation radius to be calculated to obtain the flame edge contour image;

[0006] Step 2: Determine the measurement center of the flame spread radius

[0007] Step 21: Preliminarily establish a two-dimensional coordinate system and divide the flame edge contour map into regions:

[0008] An initial two-dimensional coordinate system is established for the flame edge contour map, and the ordinate is determined by connecting the two ends of the ignition electrode. A pixel point A farthest from the ordinate is determined on the flame front surface on both sides of the ordinate. 1 and B 1 ; 1 or B1 The vertical line drawn by the pixel point to the ordinate determines the abscissa;

[0009] Determine that the two-dimensional coordinate system is divided into four regions: 0°-90° is region one; 90°-180° is region two, 180°-270° is region three, and 270°-360° is region four;

[0010] Step 22: Define the pixel points farthest from the upper end of the ignition electrode in area 1 and area 2, and the pixel points farthest from the lower end of the ignition electrode in area 3 and area 4, that is, the pixel points least affected by the ignition electrode, with the horizontal coordinate as X. bi , the vertical coordinate is Y bi ; i=1,2,3,4, representing four regions respectively;

[0011] Step 23: Calculate the flame propagation radius measurement center: Assume that the flame propagation radius measurement center is Q, then the coordinates of Q are (s, t) = ((X b1 +X b2 +X b3 +X b4 ) / 4, (Y b1 +Y b2 +Y b3 +Y b4 ) / 4);

[0012] Step 3: Calculate the calibration ratio k, which is the ratio between the size of the captured image and the corresponding pixel value in the Schlieren image;

[0013] Step 4: Determine the untrustworthy radius of the ignition electrode influence:

[0014] Step 41: Define the flame propagation radius R of the pixels farthest from the two ends of the ignition electrode in the four regions bi ;

[0015] Step 42: Calculate the radius difference in the four areas respectively: with an angle step of 1°, determine the radius extraction value R in each area iθ ; R bi As the benchmark, we get R iθ -R bi or R bi -R iθ , draw the radius difference change diagram of each area;

[0016] Step 43: Determine the radius accuracy error a%, and calculate the accuracy error standard of the radius difference change diagram: that is, calculate R bi *a% or -R bi *a%;

[0017] Step 44: Place R iθ -R bi or Rbi -R iθ and (+ / -)R bi *a% compared, exceeding (+ / -)R bi *The angle range corresponding to the partial radius difference of a% is the untrustworthy radius range of the corresponding area.

[0018] Furthermore, the horizontal coordinate and vertical coordinate of the pixel point in step 22 are specifically: b1 is the horizontal coordinate of the pixel point in a region that is least affected by the ignition electrode, X b2 is the horizontal coordinate of the pixel point in the second region that is least affected by the ignition electrode, X b3 is the horizontal coordinate of the pixel least affected by the ignition electrode in the three regions, X b4 Y is the horizontal coordinate of the pixel least affected by the ignition electrode in the four regions; b1 Y is the vertical coordinate of the pixel point in a region that is least affected by the ignition electrode. b2 Y is the ordinate of the pixel least affected by the ignition electrode in the second region. b3 Y is the ordinate of the pixel least affected by the ignition electrode in the three regions. b4 It is the vertical coordinate of the pixel point least affected by the ignition electrode in the four areas.

[0019] Furthermore, the determination of the radius extraction value in each area is specifically as follows: all the radius extraction values ​​in the four areas with an angle step of 1° are respectively: one area is R 1θ , θ corresponds to 1°, 2°, 3°......90°; the second area is R 2θ , θ corresponds to 91°, 92°, 93°......180°; the three regions are R 3θ , θ corresponds to 181°, 182°, 183°......270°; the four regions are R 4θ , θ corresponds to 271°, 272°, 273°......360°;

[0020] If there are discrete points, the radius of the edge contour points near them is selected for extraction.

[0021] The beneficial effects of the present invention are as follows: the present invention can analyze the influence of the ignition electrode on each part, thereby determining the unreliable range of the flame radius; it is not only convenient for more reasonable calculation of the flame radius, but also can distinguish the influence of the ignition electrode on the four areas, and provides certain theoretical support for the changing law of the development process of the flame radius of each part. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The edge contour image is obtained after processing the Schlieren image of the flame propagation radius.

[0023] Figure 2 Schematic diagram of the two-dimensional coordinate system in the flame edge contour diagram.

[0024] Figure 3 Schematic diagram of the area division for the flame edge contour map.

[0025] Figure 4 Schematic diagram for calculating the calibration ratio.

[0026] Figure 5 This is a radius difference change diagram for a region.

[0027] Figure 6 This is a graph showing the radius difference between the two regions.

[0028] Figure 7 This is a graph showing the radius difference changes in the three regions.

[0029] Figure 8 This is a graph showing the radius difference changes in the four regions.

[0030] Fig. 9 This is a graph showing the radius difference variation in each area.

[0031] Fig.10 It is the untrustworthy radius range of each area in the flame edge contour map. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] The present invention provides a new method for determining the untrustworthy radius range, which can determine the untrustworthy radius range of various flame radius unevenness situations, and then calculate a more reasonable flame propagation radius.

[0034] The main steps include:

[0035] Step 1: Process the Schlieren image of the flame propagation radius to be calculated to obtain the edge contour map (such as Figure 1 as shown).

[0036] Step 2: Determine the measurement center of the flame spread radius

[0037] Step 21: Figure 2 As shown, a two-dimensional coordinate system is initially established in the flame edge contour diagram: the line connecting the two ends of the ignition electrode is used as the ordinate direction, and the pixel point A perpendicular to the two ends of the ignition electrode on the flame front surface is 1 and B 1 , guarantee A 1 or B 1 The horizontal coordinates of these two pixels are the smallest or largest. 1 or B 1The direction of the vertical line drawn by these two pixel points to the ordinate is the direction of the abscissa.

[0038] Step 22: Divide the flame edge contour image in step 21 into regions, such as Figure 3 : Based on the ignition electrode, it is divided into four areas: 0°-90° is area one; 90°-180° is area two, 180°-270° is area three, and 270°-360° is area four.

[0039] Step 23: Define the horizontal coordinates (X bi (i=1,2,3,4)i represents the area) and the ordinate (Y bi (i=1,2,3,4)i represents the area, such as Figure 3 As shown in Figure 2). Because the edge contour image obtained by processing the flame pattern image is the original contour point, there is a case where the original contour point is discrete. If the horizontal coordinate and vertical coordinate of the pixel point farthest from the two ends of the ignition electrode in the four regions are discrete, the horizontal coordinate and vertical coordinate of the pixel point near it are selected. That is, X b1 is the horizontal coordinate of the pixel point in a region that is least affected by the ignition electrode, X b2 is the horizontal coordinate of the pixel point in the second region that is least affected by the ignition electrode, X b3 is the horizontal coordinate of the pixel least affected by the ignition electrode in the three regions, X b4 Y is the horizontal coordinate of the pixel least affected by the ignition electrode in the four regions; b1 Y is the vertical coordinate of the pixel point in a region that is least affected by the ignition electrode. b2 Y is the ordinate of the pixel least affected by the ignition electrode in the second region. b3 Y is the ordinate of the pixel least affected by the ignition electrode in the three regions. b4 It is the vertical coordinate of the pixel point least affected by the ignition electrode in the four areas.

[0040] Step 24: Get the flame propagation radius measurement center: Assume that the flame propagation radius measurement center is Q, and the coordinates of Q are (s, t), then the coordinates of Q are (s, t) = ((X b1 +X b2 +X b3 +X b4 ) / 4, (Y b1 +Y b2 +Y b3 +Y b4 ) / 4).

[0041] Step 3: If Figure 4 , calculate the calibration ratio k, which is the ratio between the size of the captured image and the corresponding pixel value in the Schlieren image. The calculation formula for the calibration ratio k is: k=s / s0 , s is the diameter AB of the ruler; s 0 is the diameter of the ruler image in the Schlieren image 1 B 1 .

[0042] Step 4: Determine the untrustworthy radius of the ignition electrode influence:

[0043] Step 41: Define the flame propagation radius (R bi (i=1,2,3,4) i represents the region). That is, R b1 is the flame propagation radius of the smallest pixel point affected by the ignition electrode in a region, R b2 is the flame propagation radius of the minimum pixel point affected by the ignition electrode in the two regions, R b3 is the flame propagation radius of the pixel least affected by the ignition electrode in the three regions, R b4 is the flame propagation radius of the minimum pixel point affected by the ignition electrode in the four areas.

[0044] Step 42: Calculate the radius differences in the four areas respectively:

[0045] Step 421: define the radius extraction values ​​in four regions: all the radius extraction values ​​R in a region with an angle step of 1° 1θ (θ=1°, 2°, 3°......90°), extract the value R of all radii in the second area with an angle step of 1° 2θ (θ=1°, 2°, 3°......90°), extract the value R of all radii in the three regions with an angle step of 1° 3θ (θ=1°, 2°, 3°......90°), extract the value R of all radii in the four regions with an angle step of 1° 4θ (θ=1°,2°,3°......90°).

[0046] Step 422: Calculate R of a region 1θ -R b1 or R b1 -R 1θ (θ=1°,2°,3°......90°): Take R b1 As the benchmark (the radius extraction value with the least influence from the ignition electrode and the smallest deformation is used as the reference, if there is a discrete point, the radius extraction value of the edge contour point near it is selected), R 1θ -R b1 or R b1 -R 1θ (θ=1°, 2°, 3°......90°), draw a radius difference change graph for an area, the specific results are as follows Figure 5 .

[0047] Step 423: Calculate R of the second region 2θ -R b2 or R b2 -R 2θ (θ=91°, 92°, 93°...180°): Take R b2 As the benchmark, we get R 2θ (θ=91°, 92°, 93°......180°), draw a graph showing the radius difference between the two regions. The specific results are as follows Figure 6 .

[0048] Step 424: Calculate R of three regions 3θ -R b3 or R b3 -R 3θ (θ=181°, 182°, 183°...270°): Take R b3 As the benchmark, we get R 3θ (θ=181°, 182°, 183°......270°), draw a graph of the radius difference changes in the three areas, the specific results are as follows Figure 7 .

[0049] Step 425: Calculate R of the four regions 4θ -R b4 or R b4 -R 4θ (θ=271°, 272°, 273°...360°): Take R b4 As the benchmark, we get R 4θ (θ=271°, 272°, 273°......360°), draw a graph of the radius difference changes in the four areas, the specific results are as follows Figure 8 .

[0050] Step 43: Determine the radius accuracy error. A radius accuracy error of 5% can meet the requirements of characteristic parameters such as laminar combustion speed, that is, the radius accuracy error is determined to be 5%.

[0051] Step 44: Calculate the accuracy error standard of the radius difference change diagram: that is, calculate R bi or -R bi (i=1, 2, 3, 4)*5%.

[0052] Step 45: Eliminate the untrustworthy radius of the flame:

[0053] Step 451: R 1θ -R b1 or R b1 -R 1θ(θ=1°, 2°, 3°......90°) and (+ / -)R b1 *5% for comparison, exceeding (+ / -)R b1 *The angle range corresponding to the 5% partial radius difference is the untrustworthy radius range of an area;

[0054] Step 452: R 2θ -R b2 or R b2 -R 2θ (θ=91°, 92°, 93°......180°) and (+ / -)R b2 *5% for comparison, exceeding (+ / -)R b2 *The angle range corresponding to the 5% partial radius difference is the untrustworthy radius range of the two areas;

[0055] Step 453: R 3θ -R b3 or R b3 -R 3θ (θ=181°, 182°, 183°......270°) and (+ / -)R b3 *5% for comparison, exceeding (+ / -)R b3 *The angle range corresponding to the 5% partial radius difference is the untrustworthy radius range of the three areas;

[0056] Step 454: R 4θ -R b4 or R b4 -R 4θ (θ=271°, 272°, 273°......360°) and (+ / -)R b4 *5% for comparison, exceeding (+ / -)R b4 *The angle range corresponding to the 5% partial radius difference is the untrustworthy radius range of the four areas.

[0057] Specific results such as Fig. 9 , as shown in 10, the untrusted radius range is determined as:

[0058] 46°≤α≤90°,90°≤β≤137°,212°≤ԏ≤270°,270°≤Ƴ≤314°. α is the untrusted radius range of the first area, β is the untrusted radius range of the second area, ԏ is the untrusted radius range of the third area, and Ƴ is the untrusted radius range of the fourth area.

[0059] The flame radius corresponding to the angle outside the untrustworthy radius range can be calculated according to the calibration ratio of step 3, that is, the final flame propagation radius extraction value is obtained.

Claims

1. A method for determining the range of the untrustworthy radius of a flame, characterized in that, it includes the following steps: Step 1: Preprocess the schlieren image of the flame propagation radius to be calculated to obtain the flame edge contour map; Step 2: Determine the measurement center of the flame propagation radius; Step 21: Initially establish a two-dimensional coordinate system and divide the area of the flame edge contour map: Establish an initial two-dimensional coordinate system for the flame edge contour map, determine the ordinate with the line connecting the two ends of the ignition electrode, and respectively determine a pixel point A that is farthest from the ordinate on the flame front surfaces on both the left and right sides of the ordinate. 1 and B 1 ; Use the vertical line made by pixel point A 1 or B 1 to the ordinate to determine the abscissa. Determine that the four areas divided by the two-dimensional coordinate system are: 0°-90° is one area; 90°-180° is the second area, 180°-270° is the third area, and 270°-360° is the fourth area; Step 22: Define respectively the pixel points in Region 1 and Region 2 that are farthest from the upper end of the ignition electrode, and the pixel points in Region 3 and Region 4 that are farthest from the lower end of the ignition electrode, that is, the pixel points least affected by the ignition electrode, with the abscissa being X bi , and the ordinate being Y bi ; i = 1, 2, 3, 4, respectively representing the four regions; Step 23: Calculate the center of the flame propagation radius measurement: Let the center of the flame propagation radius measurement be Q, and the coordinates of Q be (s, t) = ((X b1 + X b2 + X b3 + X b4 ) / 4, (Y b1 + Y b2 + Y b3 + Y b4 ) / 4); Step 3: Calculate the calibration ratio k, that is, the ratio between the size of the captured image and the corresponding pixel value in the schlieren image; Step 4: Determine the range of the untrustworthy radius affected by the ignition electrode: Step 41: Define the flame propagation radius R of the pixel points farthest from both ends of the ignition electrode in four regions bi ; Step 42: Calculate the radius differences in the four regions respectively: With an angular step of 1°, determine the radius extraction value R in each region iθ ; Taking R bi as the reference, obtain R iθ -R bi or R bi -R iθ , and draw the change diagram of the radius differences in each region; Step 43: Determine the radius precision error a%, and calculate the precision error standard of the radius difference change diagram: that is, calculate R bi *a% or -R bi *a%; Step 44: Compare R iθ -R bi or R bi -R iθ with (+ / -)R bi *a%, and the angular range corresponding to the partial radius difference exceeding (+ / -)R bi *a% is the untrusted radius range of the corresponding area; In step 22, the abscissa and ordinate of the pixel point are specifically: X b1 is the abscissa of the pixel point with the least influence of the ignition electrode in area one, X b2 is the abscissa of the pixel point with the least influence of the ignition electrode in area two, X b3 is the abscissa of the pixel point with the least influence of the ignition electrode in area three, X b4 is the abscissa of the pixel point with the least influence of the ignition electrode in area four; Y b1 is the ordinate of the pixel point with the least influence of the ignition electrode in area one, Y b2 is the ordinate of the pixel point with the least influence of the ignition electrode in area two, Y b3 is the ordinate of the pixel point with the least influence of the ignition electrode in area three, Y b4 is the ordinate of the pixel point with the least influence of the ignition electrode in area four.

2. The method for determining the range of the untrustworthy radius of a flame according to claim 1, characterized in that, the specific method for determining the radius extraction value in each area is: All the radius extraction values at an angular step of 1° in the four regions are as follows: for the first region, it is R 1θ , where θ corresponds to 1°, 2°, 3°......90°; for the second region, it is R 2θ , where θ corresponds to 91°, 92°, 93°......180°; for the third region, it is R 3θ , where θ corresponds to 181°, 182°, 183°......270°; for the fourth region, it is R 4θ , where θ corresponds to 271°, 272°, 273°......360°; If there are discrete points, select the radius extraction value of the edge contour points near them.

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