Method and device for calculating refractive index distribution of corona discharge channel

Abstract

The application provides a method, device and equipment for calculating the refractive index distribution of a corona discharge channel and a storage medium, and the method comprises the following steps: obtaining a schlieren image of corona discharge, determining a light deflection angle correction curve corresponding to a target discharge channel; determining an original deflection angle corresponding to each pixel point in the schlieren image of corona discharge; performing interpolation processing on the original deflection angle corresponding to each pixel point, determining the axis of the target discharge channel according to the deflection angle data points, and determining an axial symmetry coordinate system of the schlieren image of corona discharge; determining the corresponding relationship between the deflection angle data points and the refractive index based on a preset Abel integral formula and the axial symmetry coordinate system, and solving the singular points of the Abel integral formula by approximation; and calculating the radial distribution data of the refractive index of the target discharge channel according to the singular points obtained by approximation and the corresponding relationship between the deflection angle data points and the refractive index. The application can increase the amount of reference information provided by the corona discharge detection technology to meet the quantitative analysis requirements of corona discharge.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of corona detection, in particular to a method and device for calculating the refractive index distribution of a corona discharge channel, equipment and a storage medium. BACKGROUND

[0002] Corona discharge is a kind of discharge phenomenon widely existing on power transmission lines. The audible noise caused by corona discharge and its disturbance to the public are one of the main factors restricting the design and construction of power transmission lines. The image acquisition and analysis technology of corona discharge is the technical basis for researchers to analyze the characteristics of corona discharge, study the mechanism of audible noise caused by corona discharge, and develop relevant noise control schemes. The existing image acquisition and analysis technology of corona discharge is mainly related to ultraviolet imaging technology.

[0003] Corona discharge has the characteristics of small size, weak light emission and ultraviolet light emission band. The basic principle of the existing technology is to develop an imaging technology capable of collecting light in the wavelength range of 200nm-400nm based on the light emission band of corona discharge. This kind of technology is not suitable for quantitative analysis of air density changes and audible noise levels caused by corona discharge in principle. The images collected can only provide qualitative reference for the study of corona discharge, and the reference information is limited, which cannot meet the quantitative analysis requirements of corona discharge. SUMMARY

[0004] The present application aims to provide a method and device for calculating the refractive index distribution of a corona discharge channel, equipment and a storage medium to solve the above technical problems, so as to increase the amount of reference information provided by the corona discharge detection technology and meet the quantitative analysis requirements of corona discharge.

[0005] In order to solve the above technical problems, the present application provides a method for calculating the refractive index distribution of a corona discharge channel, comprising:

[0006] Obtaining a schlieren image of corona discharge based on a pre-built linear schlieren light path, and determining a light deflection angle correction curve corresponding to a target discharge channel according to the schlieren image of corona discharge;

[0007] Determining the original deflection angle corresponding to each pixel point in the schlieren image of corona discharge based on the light deflection angle correction curve and the gray value of each pixel point in the schlieren image of corona discharge;

[0008] Performing interpolation processing on the original deflection angle corresponding to each pixel point by using a preset data interpolation method to obtain deflection angle data points after interpolation processing, determining the axis of the target discharge channel according to the deflection angle data points, and determining an axisymmetric coordinate system of the schlieren image of corona discharge based on the axis;

[0009] Determine the corresponding relationship between the deflection angle data points and the refractive index based on the preset Abel integral formula and the axisymmetric coordinate system, and use the improved Gauss-Legendre method to approximate and solve the singular points of the Abel integral formula;

[0010] According to the singular points obtained by approximation and solving and the corresponding relationship between the deflection angle data points and the refractive index, the refractive index radial distribution data of the target discharge channel is calculated.

[0011] Further, the method comprises the following steps of:

[0012] The quantitative relationship between the light deflection amount and the gray scale change amount of each pixel point in the corona discharge schlieren image is determined by using the correction schlieren method.

[0013] The light deflection angle correction curve corresponding to the target discharge channel is determined based on the quantitative relationship between the light deflection amount and the gray scale change amount.

[0014] Further, the preset data interpolation method is a bicubic interpolation method.

[0015] Further, the approximation and solving of the singular points of the Abel integral formula is performed by using a linear fitting method.

[0016] The application further provides a device for calculating the refractive index distribution of a corona discharge channel, which comprises:

[0017] A curve correction module is configured to obtain a corona discharge schlieren image based on a pre-built straight-line schlieren light path, and determine a light deflection angle correction curve corresponding to a target discharge channel according to the corona discharge schlieren image.

[0018] A deflection angle determination module is configured to determine the original deflection angle corresponding to each pixel point in the corona discharge schlieren image based on the light deflection angle correction curve and the gray scale value of each pixel point in the corona discharge schlieren image.

[0019] An axis determination module is configured to perform interpolation processing on the original deflection angle corresponding to each pixel point by using a preset data interpolation method, obtain deflection angle data points after interpolation processing, determine the axis of the target discharge channel according to the deflection angle data points, and determine the axisymmetric coordinate system of the corona discharge schlieren image based on the axis.

[0020] A singular point solving module is configured to determine the corresponding relationship between the deflection angle data points and the refractive index based on the preset Abel integral formula and the axisymmetric coordinate system, and use the improved Gauss-Legendre method to approximate and solve the singular points of the Abel integral formula.

[0021] A distribution calculation module is configured to calculate the refractive index radial distribution data of the target discharge channel according to the corresponding relationship between the inflection point after approximation solving and the deflection angle data point and the refractive index.

[0022] The application further provides a terminal device comprising a processor and a memory storing a computer program, and the processor implements the calculation method of the refractive index distribution of the corona discharge channel when executing the computer program.

[0023] The application further provides a non-transitory computer-readable storage medium storing a computer program, and the computer program implements the calculation method of the refractive index distribution of the corona discharge channel when executed by a processor.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] The application provides a calculation method, device and equipment of the refractive index distribution of a corona discharge channel and a storage medium, and the method comprises the following steps: acquiring a corona discharge schlieren image, determining a light deflection angle correction curve corresponding to a target discharge channel, determining original deflection angles corresponding to each pixel point in the corona discharge schlieren image, performing interpolation processing on the original deflection angles corresponding to the pixel points, determining an axis of the target discharge channel according to deflection angle data points, and determining an axial symmetry coordinate system of the corona discharge schlieren image, determining a corresponding relationship between the deflection angle data points and the refractive index based on a preset Abel integral formula and the axial symmetry coordinate system, performing approximation solving on an inflection point of the Abel integral formula, and calculating refractive index radial distribution data of the target discharge channel according to the inflection point after approximation solving and the corresponding relationship between the deflection angle data points and the refractive index. The application can increase the amount of reference information provided by the corona discharge detection technology to meet the quantitative analysis requirements of the corona discharge. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 FIG. 1 is a flowchart of the calculation method of the refractive index distribution of the corona discharge channel provided by the application;

[0027] Figure 2 FIG. 2 is a schematic diagram of a straight-line schlieren light path arrangement provided by the application;

[0028] Figure 3 FIG. 3 is a schematic diagram of the equivalent relationship of the gray scale change caused by the knife edge displacement and the light offset provided by the application;

[0029] Figure 4 FIG. 4 is a schematic diagram of a deflection angle correction curve provided by the application;

[0030] Figure 5 FIG. 5 is a schematic diagram of the comparison before and after the deflection angle interpolation processing provided by the application;

[0031] Figure 6 is a schematic diagram of a linear approximation calculation method of singular points provided by the present application;

[0032] Figure 7 is a schematic diagram of a deflection angle simulation distribution and sampling points provided by the present application;

[0033] Figure 8 is a schematic diagram of a refractive index difference simulation distribution and reconstruction results provided by the present application;

[0034] Figure 9 is a schematic diagram of refractive index difference reconstruction error under different sampling points provided by the present application;

[0035] Figure 10 is a schematic diagram of a corona discharge schlieren image of a needle end provided by the present application;

[0036] Figure 11 is a schematic diagram of refractive index field reconstruction results of a, b, and c positions in a corona discharge channel provided by the present application;

[0037] Figure 12 is a schematic diagram of a structure of a computing device of a corona discharge channel refractive index distribution provided by the present application. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0039] Please refer to Figure 1 The embodiments of the present application provide a computing method of a corona discharge channel refractive index distribution, which can include the following steps:

[0040] S1, obtaining a corona discharge schlieren image based on a pre-built linear schlieren light path, and determining a light deflection angle correction curve corresponding to a target discharge channel according to the corona discharge schlieren image;

[0041] S2, determining an original deflection angle corresponding to each pixel point in the corona discharge schlieren image based on the light deflection angle correction curve and a gray value of each pixel point in the corona discharge schlieren image;

[0042] S3, the original deflection angle corresponding to each pixel point is processed by using a preset data interpolation method to obtain a deflection angle data point after interpolation processing, the axis of the target discharge channel is determined according to the deflection angle data point, and the axisymmetric coordinate system of the corona discharge schlieren image is determined based on the axis;

[0043] S4, the corresponding relationship between the deflection angle data point and the refractive index is determined based on a preset Abel integral formula and the axisymmetric coordinate system, and an improved Gauss-Legendre method is used to approximate and solve singular points of the Abel integral formula;

[0044] S5, the refractive index radial distribution data of the target discharge channel are calculated according to the singular points after approximation and solving and the corresponding relationship between the deflection angle data point and the refractive index.

[0045] In the embodiment of the application, further, the light deflection angle correction curve corresponding to the target discharge channel is determined according to the corona discharge schlieren image, comprising:

[0046] The quantitative relationship between the light deflection amount and the gray scale change amount of each pixel point in the corona discharge schlieren image is determined by using a correction schlieren method;

[0047] The light deflection angle correction curve corresponding to the target discharge channel is determined based on the quantitative relationship between the light deflection amount and the gray scale change amount.

[0048] In the embodiment of the application, further, the preset data interpolation method is a bicubic interpolation method.

[0049] In the embodiment of the application, further, the singular points of the Abel integral formula are approximated and solved by using a linear fitting method.

[0050] Based on the above scheme, in order to better understand the calculation method of the refractive index distribution of the corona discharge channel provided by the embodiment of the application, the following is described in detail:

[0051] It should be noted that, in order to solve the technical problem of quantitatively analyzing the corona discharge characteristics according to the image, the embodiment of the application starts from the principle of air density change caused by corona discharge, uses a transmission light path to quantitatively collect the deflection angle of the corona discharge channel, develops a matching image interpolation and singular point approximation method to process the deflection angle scattered points, and obtains the refractive index distribution of the corona discharge channel. The refractive index distribution can be used to further quantitatively analyze the pressure distribution, density distribution and temperature distribution of the corona discharge channel.

[0052] (1) Establishing a corona discharge channel deflection angle system and a correction curve

[0053] The linear schlieren light path is built to measure the corona discharge channel. The probe light emitted by the light source of the schlieren system is deflected when passing through the discharge channel. The deflected probe light is offset up and down at the focal point of the lens, and the gray scale change at the discharge channel is shown in the image. The knife edge placed at the focal point of the lens converts the gray scale information of the discharge area into deflection angle data. Figure 2 .

[0054] Figure 2 The spherical light emitted by the LED in (b) is integrated into parallel probe light by the cemented lens to pass through the discharge channel. Assuming that the light intensity entering and exiting the discharge channel is I0 and I, respectively, the relationship between the two is known by the Lambert-Beer law:

[0055] I = I0·exp(-βd) (1)

[0056] In the formula, β is the attenuation coefficient, and d is the thickness of the discharge channel, in mm. The change of light intensity at the knife edge has two parts: 1. The discharge channel causes the exiting light intensity to decay exponentially, and the gray scale of the image at the knife edge will change; 2. The parallel probe light is deflected after passing through the discharge channel with a refractive index of n, thereby causing the light intensity (gray scale) at the knife edge to change, wherein the gray scale change caused by the deflection of the probe light is:

[0057] ΔI = ±(α·f2) (2)

[0058] In the formula, α is the deflection angle of the exiting light, in rad; f2 is the focal length of the cemented lens, in mm; and ΔI is the light intensity change, in cd. The present application uses a correction lens for quantitative schlieren system, and the light attenuation coefficient β of the discharge channel can be ignored; at the same time, the thickness d of the corona discharge channel (the corona diameter is about 1 mm) is much smaller than the optical path (2 m) of the schlieren system, and the exiting light I = I0 can be approximated, so the gray scale change (light intensity change) of the discharge channel measured by the schlieren system can be regarded as the change of the light offset amount corresponding to the light deflection angle α. The light offset amount caused by the light deflection angle α is equivalent to the displacement ΔI of the knife edge, and the light deflection angle α is calculated, Figure 3 which is the equivalent relationship of the image gray scale change caused by the light offset and the knife edge displacement in the schlieren system.

[0059] Figure 3 (b) moves the knife edge of the schlieren system by ΔI to make the light intensity change ΔI equivalent to the light intensity change caused by the light deflection, as shown in (a) of Figure 3 . The change of light intensity ΔI is shown as the gray scale change ΔG of the schlieren image in the schlieren image taken by the high-speed camera. Finally, according to the quantitative displacement ΔI of the knife edge, the relationship between the gray scale ΔG and the displacement ΔI can be obtained, as shown in formula (3):

[0060] Δl=f(ΔG) (3)

[0061] In the formula, Δl is the knife edge displacement, in mm. Substituting equation (3) into equation (2), we can obtain the light deflection angle caused by the discharge channel as follows:

[0062] α=Δl / f2 (4)

[0063] The key step in quantitatively calculating the optical deflection angle is to obtain the relationship between the gray change ΔG in the discharge region and the knife edge displacement Δl, i.e., the functional relationship Δl=f(ΔG) shown in equation (3). There are two methods to determine this functional relationship. The first method is as follows: Figure 3 As shown, one method involves manually adjusting the blade displacement to obtain the corresponding grayscale change (quantitative schlieren method). Another method involves placing an object with a known refractive index in the optical path and directly obtaining the quantitative relationship between the light offset and the grayscale change through the image (corrected schlieren method). This invention uses a plano-concave lens with a diameter of 25mm and a focal length of 1000mm to generate a corrected schlieren image, and simultaneously uses the method of manually adjusting the blade to obtain a quantitative curve. The resulting corrected curve is shown in the figure. Figure 4 .

[0064] Figure 4 The center dot curve is the calibration curve generated by the calibration lens, and the box curve is the quantitative curve obtained by manually adjusting the knife edge. The calculation process for the data points in the calibration curve is as follows:

[0065] 1) Find the center point (r0, G) of the plano-concave lens image. B Extract one row of pixels (r) i G i ), where r i It is pixel coordinates, G i It refers to pixel grayscale.

[0066] 2) Gray level G of each pixel i Subtract background grayscale G B The grayscale change ΔG is obtained.

[0067] 3) Establish a coordinate system r0 with the point where the pixel gray level is the same as the background gray level as the 0 point, and obtain the radial coordinate r corresponding to each pixel. i -r0, substituting into equation (5), we can calculate the deflection angle α of each pixel. i .

[0068]

[0069] In the formula, f t It is the focal length of the plano-concave lens, with a value of f. t =1000mm. According to... Figure 4The difference between the dotted curve (corrected lens) and the square box curve (manual quantification) in the figure is obvious when the gray scale is less than 80, and the curve generated by the corrected lens is smoother and has more sampling points, while the curve generated by manual quantification has fewer sampling points and is not smooth when the gray scale is less than 80, indicating that the corrected lens used in the embodiment of the application has more advantages than the traditional manual quantification.

[0070] (2) An interpolation method for the deflection angle data of the corona discharge channel is established.

[0071] The gas temperature of the corona discharge channel is low, there is no obvious thermal expansion phenomenon, and the size of the discharge channel is very small. Since the heat exchange with the outside is not obvious, the corona discharge channel has the characteristics of fewer sampling points and more regular point distribution. Figure 5 The deflection angle data interpolation method of the corona discharge channel is illustrated by taking the image in the figure as an example. Figure 5 is a comparison diagram of the original deflection angle scatter points and the deflection angle obtained after image preprocessing.

[0072] Figure 5 The square scatter points in the figure are the original deflection angle scatter points of the discharge channel. It can be seen that the axial position (deflection angle of 0) of the discharge channel cannot be directly found by the original deflection angle data points. The scatter points only show the approximate outline of the channel. The cross scatter points, the dot scatter points and the solid line are the results obtained by using bilinear interpolation, bicubic interpolation and curve fitting method respectively. As can be seen from the figure, due to the small number of original deflection angle sampling points, the bilinear interpolation appears to be not smooth. The fitting curve method may cause the deflection angle to be not monotonic, resulting in a small refractive index calculation result. The bicubic interpolation can directly determine the axial center of the discharge channel on the basis of ensuring the monotonicity and smoothness of the deflection angle. Therefore, the bicubic interpolation is used for preprocessing of the corona discharge channel.

[0073] (3) An improved Gaussian-Legendre method for approaching the deflection angle singular point is established.

[0074] The discrete deflection angle data scatter points a obtained from the striae image are the line integrals of the probe light along the x-axis direction of the discharge channel. Assuming that the discharge channel is axisymmetric, the corresponding relationship between the deflection angle data points and the refractive index can be described by using the Abel integral, as shown in formula (6):

[0075]

[0076] In the formula, R represents the boundary radius of the discharge channel, unit: mm; r represents the radial distance, unit: mm; and the inverse Abel equation corresponding to formula (6) is:

[0077]

[0078] In the formula, γ0 is the background refractive index of the measured space, γ(r) is the radial distribution of the refractive index, and α(x) is the measured deflection angle data. Each integral point of the discharge channel radial coordinate r in formula (7) is a singular point, and the solution of formula (7) must use a numerical calculation method, and the improved Guass-Legendre calculation method is proposed for the solution of formula (7).

[0079] The integral limit of the independent variable in formula (7) is r~R, and there is 1 / (x 2 -r 2 )0.5=∞ (singular point) at each calculation point x=r in the radial direction, and the analytic solution cannot be calculated at the singular point position of x=r, and the position of the singular point cannot be directly used in the numerical integration method with trapezoidal, rectangular and Simpson forms. Therefore, the integral interval [r, R] is reconstructed by using linear transformation, as shown in formula (8).

[0080]

[0081] By formula (8), the integral interval x∈[r, R] can be transformed into t∈[-1, 1], and the definite integral substitution integration method can be obtained:

[0082]

[0083] In this paper, the discrete form of formula (9) is further constructed by using the Guass-Legendre formula:

[0084]

[0085] In the formula, A k is the quadrature coefficient, and A k =(R-r) / 2. According to formula (9) and (10), the function value f(r) at the singular point [r, r] of the discrete interval [r, R] is set to 0 by the quadrature coefficient A k =(r-r) / 2, and the algorithm can approximate the singular point by increasing the number N of discrete intervals. The linear fitting method is used to construct the discrete region near the singular point in the application, so as to improve the calculation accuracy at the singular point. Figure 5 The deflection angle scattered points obtained after bicubic interpolation are used to illustrate the approximation method of the singular point, Figure 6 is Figure 5 the deflection angle scattered points obtained after bicubic interpolation.

[0086] Figure 6 The data scattered points shown in the formula are from the schlieren image, and the radial coordinates and deflection angles of the scattered points are known. The straight line equation α(r)=kr+b can be constructed between two adjacent points, Figure 6 Taking the points r0 and r 10 in the formula as an example, the straight line equation is:

[0087]

[0088] According to the straight line equation, the deflection angle a(r0+dr) of the point r0+dr near the singular point r0 can be directly obtained. When the point r0+dr is used to replace the point r0 in the calculation of formula (9), the problem of infinite value caused by 1 / (y 2 -r 2 ) 0.5 =∞ can be avoided. The equation of the replacement point r0+dr is known, so the calculation accuracy can be artificially controlled by changing the value of dr.

[0089] (4) Reconstruction of the refractive index distribution of the corona discharge channel:

[0090] Based on the above scheme, the three-dimensional refractive index distribution of the corona discharge channel is reconstructed according to the following steps:

[0091] 1) Build a straight-line schlieren light path, and obtain the correction curve of the deflection angle by adjusting the knife edge or the correction lens;

[0092] 2) Use bicubic interpolation to interpolate the original deflection angle scattered points to determine the axis of the discharge channel;

[0093] 3) Use the improved Gauss-Legendre method to approximate the singular point of the Abel integral formula of the refractive index;

[0094] 4) According to the axial symmetry of the discharge channel, the radial distribution of the refractive index of the corona discharge channel is calculated using formula (7).

[0095] The following specific implementation cases are described:

[0096] (1) Accuracy experiment of the refractive index reconstruction method:

[0097] The improved Gauss-Legendre algorithm is used to solve the Abel inverse transform equation to reconstruct the refractive index field of the corona discharge channel. The simplest method to verify the algorithm is to use the equation to construct a simulated discharge channel deflection angle and refractive index distribution, obtain the deflection angle scattered points by resampling, and finally reconstruct the refractive index distribution curve using the improved Gauss-Legendre algorithm. The accuracy of the algorithm is obtained by comparing with the original curve. The temperature distribution and current distribution of the gas discharge channel under atmospheric pressure are close to the Gaussian distribution. Therefore, the Gaussian function is used to construct the simulated refractive index and deflection angle distribution to verify the following steps:

[0098] 1) Take the standard deviation as 0.1618 (shape parameter) and the mean value as 0 (position parameter), and use the following formula (12) to construct the simulated discharge channel refractive index distribution function.

[0099]

[0100] where subscript moni represents the simulated discharge channel refractive index function, σ moni , μ moni are shape parameter and position parameter respectively, n0 is the background refractive index of air, r is the radial coordinate.

[0101] 2) The simulated discharge channel deflection angle distribution can be obtained by substituting equation (12) into equation (6) to calculate the Abel inverse transform.

[0102] 3) The simulated discharge channel deflection angle distribution is resampled, and the number of sampling points is specified by human.

[0103] 4) The improved Gauss-Legendre algorithm is used to calculate the scattered deflection angle points obtained by sampling to obtain the reconstructed refractive index distribution.

[0104] 5) The reconstructed refractive index distribution curve is compared with the original refractive index distribution curve to verify the accuracy of the algorithm.

[0105] Figure 7 is the simulated deflection angle distribution obtained by substituting equation (12) into equation (6) and the discrete sampling points of the distribution, where the radial coordinate is a normalized value.

[0106] In this example, 61 points are sampled for the simulated deflection angle with a step size of 0.01, 7 points are sampled with a step size of 0.1, and finally one sampling point is added in the range of 0-0.1 in the radial direction based on the 0.1 step size. The three sampling point numbers are used to reconstruct the refractive index distribution. The refractive index reconstruction results obtained by calculating the three sampling point numbers and the original simulated refractive index distribution curve are shown in Figure 8 .

[0107] Figure 8 The solid line, circle, square and triangle in the figure are the simulated refractive index distribution curve and the refractive index difference reconstruction results under the three sampling point conditions. Figure 8 It can be seen from the figure that when 61 sampling points are used, the reconstructed refractive index difference scattered points are in good agreement with the original curve, when 7 sampling points are used, the refractive index difference at the axial position is small and the refractive index difference at the radial position of 0.1 is large, and when 8 sampling points are used, the reconstruction effect is obviously improved compared with 7 sampling points. The relative error of the reconstructed refractive index difference and the original curve is shown in Figure 9 to quantitatively analyze the accuracy of the algorithm and its influencing factors.

[0108] Figure 9 is an error diagram of the refractive index difference under different sampling point numbers, where the circle, square and triangle are the reconstruction errors when 61, 7 and 8 sampling points are set respectively. Figure 9It can be seen from the table that the relative error of the reconstructed refractive index difference is within 1% when 61 sampling points are set, and the maximum error (about 0.7%) appears at the axis of the simulated discharge channel, and the error at the axis is obviously (about 25%) when 7 sampling points are set, and the error decreases with the increase of the radial distance, which is because the first derivative (the gradient of the deflection angle) of the deflection angle with respect to the radial distance in the Abel inverse transform equation is used as the input, so the area with a larger gradient of the deflection angle in the original deflection angle curve is more likely to have a reconstruction error, and the reconstruction error at the axis is reduced to within 5% when 8 sampling points are used for the refractive index difference reconstruction, and the reconstruction error is less than 1% when the radial coordinate is greater than 0.04.

[0109] By Figure 8 、 Figure 9 and the corresponding analysis, it can be seen that the improved Gauss Legendre algorithm proposed in the embodiment of the application has a good refractive index difference reconstruction effect under the condition that the deflection angle sampling points are sufficient, and the reconstruction accuracy of the area with a larger gradient of the deflection angle is very sensitive to the number of sampling points, and the spatial resolution of the schlieren image is improved at the hardware level or the original schlieren image is processed by using the interpolation technology, so that the accuracy of the refractive index reconstruction can be improved.

[0110] (2) Refractive index reconstruction experiment of a corona discharge channel

[0111] As Figure 10 is a schlieren image of the needle end of a needle-plate interfacial discharge structure.

[0112] Figure 10 The a, b and c positions of the corona channel from the needle to the plate are marked in the table, and the refractive index field reconstruction results corresponding to the three positions of the corona discharge channel in the table are obtained by using the refractive index distribution reconstruction method proposed in the embodiment. Figure 10 The refractive index field reconstruction results corresponding to the three positions of the corona discharge channel in the table are shown in the following table. Figure 11 As shown in the table.

[0113] By Figure 11 It can be seen from the reconstruction results of the refractive index distribution in the table that the method of the embodiment can obtain a relatively smooth and continuous refractive index distribution, and because the gas density of the discharge channel is less than that of air, the refractive index difference is less than 0.

[0114] Compared with the prior art, the embodiment of the application has the following beneficial effects:

[0115] Compared with the existing ultraviolet camera method which can only determine whether there is a corona and cannot quantitatively calculate the corona characteristic parameters, the refractive index distribution reconstruction technology of the corona discharge provided in the embodiment of the application solves the technical problem of quantitatively analyzing the refractive index parameters in the corona discharge channel, and lays a foundation for further analyzing the density and pressure of the corona, wherein the deflection angle data interpolation and singularity approximation method contained therein overcomes the difficulty of small size of the corona discharge channel, image processing and quantitative calculation, and breaks through the technical bottleneck of quantitative analysis of the characteristics of the corona discharge channel.

[0116] It should be noted that, for the above method or process embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the embodiments of the present application are not limited by the order of the described actions, because according to the embodiments of the present application, certain steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all optional embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0117] Please refer to Figure 12 The embodiment of the present application also provides a refractive index distribution calculation device of a corona discharge channel, comprising:

[0118] A curve correction module 1 is configured to obtain a corona discharge schlieren image based on a pre-built straight-line type schlieren light path, and determine a light deflection angle correction curve corresponding to a target discharge channel according to the corona discharge schlieren image.

[0119] A deflection angle determination module 2 is configured to determine an original deflection angle corresponding to each pixel point in the corona discharge schlieren image based on the light deflection angle correction curve and the gray value of each pixel point in the corona discharge schlieren image.

[0120] An axis determination module 3 is configured to perform interpolation processing on the original deflection angle corresponding to each pixel point by using a preset data interpolation method to obtain deflection angle data points after interpolation processing, determine an axis of the target discharge channel according to the deflection angle data points, and determine an axisymmetric coordinate system of the corona discharge schlieren image based on the axis.

[0121] A singularity solving module 4 is configured to determine a corresponding relationship between the deflection angle data points and the refractive index based on a preset Abel integral formula and the axisymmetric coordinate system, and perform approximation solving on the singularity of the Abel integral formula by using an improved Gauss-Legendre method.

[0122] A distribution calculation module 5 is configured to calculate the radial distribution data of the refractive index of the target discharge channel according to the singularity after approximation solving and the corresponding relationship between the deflection angle data points and the refractive index.

[0123] In the embodiment of the present application, further, the curve correction module 1 is specifically used for:

[0124] The quantitative relationship between the light deflection and the gray scale variation of each pixel point in the corona discharge schlieren image is determined by using a correction schlieren method.

[0125] The light deflection angle correction curve corresponding to the target discharge channel is determined based on the quantitative relationship between the light deflection and the gray scale variation.

[0126] In the embodiment of the present application, further, the preset data interpolation method is a bicubic interpolation method.

[0127] In the embodiment of the present application, further, the singular point of the Abel integral formula is solved by using a linear fitting method.

[0128] It can be understood that the above-mentioned device embodiment is corresponding to the method embodiment of the present application, and the device for calculating the refractive index distribution of the corona discharge channel provided by the embodiment of the present application can realize the method for calculating the refractive index distribution of the corona discharge channel provided by any one of the method embodiments of the present application.

[0129] The present application also provides a non-transitory computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement any one of the methods for calculating the refractive index distribution of the corona discharge channel.

[0130] It should be noted that the device embodiments described above are only schematic, wherein the units described as separate components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., they can be located in one place, or distributed on multiple network units. Part or all of the modules can be selected according to actual needs to achieve the purpose of the present embodiment. In addition, the connection relationship between the modules in the device embodiment provided by the present application indicates that there is a communication connection between them, which can be realized as one or more communication buses or signal lines. Those skilled in the art can understand and implement it without creative labor.

[0131] Those skilled in the art can clearly understand that, in order to facilitate and be brief, the specific working process of the above-mentioned device can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0132] The terminal device can be a desktop computer, a notebook computer, a palm computer, a cloud server and other computing devices. The terminal device can include, but is not limited to, a processor, a memory.

[0133] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor or the like, and is a control center of the terminal device, which connects all parts of the terminal device through various interfaces and lines.

[0134] The memory can be used to store the computer program, and the processor realizes various functions of the terminal device by running or executing the computer program stored in the memory and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application program required by a function, etc.; and the data storage area can store data created according to the use of the mobile phone, etc. In addition, the memory can include a high-speed random access memory, and can also include a nonvolatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other volatile solid-state memory device.

[0135] The storage medium is a computer readable storage medium, and the computer program is stored in the computer readable storage medium. When the computer program is executed by a processor, steps of each method embodiment described above can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0136] The above is the preferred embodiment of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the present application.

Claims

1. A method of calculating the refractive index profile of a corona discharge channel, characterized by, The method comprises the following steps: Based on the pre-built linear schlieren light path, a corona discharge schlieren image is obtained, and a light deflection angle correction curve corresponding to a target discharge channel is determined according to the corona discharge schlieren image; Based on the light deflection angle correction curve and the gray value of each pixel point in the corona discharge schlieren image, the original deflection angle corresponding to each pixel point in the corona discharge schlieren image is determined; The original deflection angle corresponding to each pixel point is processed by using a preset data interpolation method to obtain deflection angle data points after interpolation processing, the axis of the target discharge channel is determined according to the deflection angle data points, and an axisymmetric coordinate system of the corona discharge schlieren image is determined based on the axis; Based on a preset Abel integral formula and the axisymmetric coordinate system, a corresponding relationship between the deflection angle data points and the refractive index is determined, and an improved Gauss-Legendre method is used to approximate and solve singular points of the Abel integral formula; According to the approximated singular points and the corresponding relationship between the deflection angle data points and the refractive index, the refractive index radial distribution data of the target discharge channel is calculated; The corresponding relationship is represented as: ； wherein α(x) is the measured deflection angle data, R represents the boundary radius of the discharge channel, γ(r) is the refractive index radial distribution, r represents the radial distance, x represents the radial coordinate of the calculation point, γ 0 is the background refractive index of the measured space; The refractive index radial distribution data is calculated by using the following discharge channel refractive index distribution function: ； wherein represents a simulated discharge channel refractive index function, σ moni is a shape parameter, μ moni is a position parameter, n 0 is the background refractive index of air.

2. The method of claim 1, wherein the method is characterized by: The light deflection angle correction curve corresponding to the target discharge channel is determined according to the corona discharge schlieren image, which comprises the following steps: The quantitative relationship between the light deflection and the gray value change of each pixel point in the corona discharge schlieren image is determined by using a correction schlieren method; Based on the quantitative relationship between the light deflection and the gray value change, the light deflection angle correction curve corresponding to the target discharge channel is determined.

3. The method of claim 1, wherein the method further comprises: The preset data interpolation method is a bicubic interpolation method.

4. The method of claim 1, wherein the method is characterized by: The singular points of the Abel integral formula are approximated and solved by using a linear fitting method.

5. An apparatus for calculating the refractive index profile of a corona discharge channel, characterized by The method comprises the following steps: A curve correction module is used to obtain a corona discharge schlieren image based on a pre-built linear schlieren light path, and a light deflection angle correction curve corresponding to a target discharge channel is determined according to the corona discharge schlieren image; A deflection angle determination module is used to determine the original deflection angle corresponding to each pixel point in the corona discharge schlieren image based on the light deflection angle correction curve and the gray value of each pixel point in the corona discharge schlieren image; An axis determination module is used to process the original deflection angle corresponding to each pixel point by using a preset data interpolation method to obtain deflection angle data points after interpolation processing, determine the axis of the target discharge channel according to the deflection angle data points, and determine an axisymmetric coordinate system of the corona discharge schlieren image based on the axis; A singular point solving module is used to determine a corresponding relationship between the deflection angle data points and the refractive index based on a preset Abel integral formula and the axisymmetric coordinate system, and an improved Gauss-Legendre method is used to approximate and solve singular points of the Abel integral formula; A distribution calculation module is used to calculate the refractive index radial distribution data of the target discharge channel according to the approximated singular points and the corresponding relationship between the deflection angle data points and the refractive index; The corresponding relationship is represented as: ； wherein α(x) is the measured deflection angle data, R represents the boundary radius of the discharge channel, γ(r) is the refractive index radial distribution, r represents the radial distance, x represents the radial coordinate of the calculation point, γ 0 is the background refractive index of the measured space; The refractive index radial distribution data is calculated by using a discharge channel refractive index distribution function as follows: ； wherein represents the simulated discharge channel refractive index function, σ moni is a shape parameter, μ moni is a position parameter, n 0 is the background refractive index of air.

6. The device for calculating the refractive index profile of a corona discharge channel according to claim 5, characterized in that The curve correction module is specifically configured to: Determine the quantitative relationship between the light deflection and the gray scale variation of each pixel point in the corona discharge schlieren image by using a correction schlieren method. Determine the light deflection angle correction curve corresponding to the target discharge channel based on the quantitative relationship between the light deflection and the gray scale variation.

7. The device for calculating the refractive index profile of a corona discharge channel according to claim 5, characterized in that The preset data interpolation method is a bicubic interpolation method.

8. The device for calculating the refractive index profile of a corona discharge channel according to claim 5, characterized in that, The singular point of the Abel integral formula is approximated and solved by using a linear fitting method.

9. A terminal device comprising a processor and a memory having a computer program stored therein, characterized in that, The processor executes the computer program to implement the calculation method of the corona discharge channel refractive index distribution in any one of claims 1 to 4.

10. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the calculation method of the corona discharge channel refractive index distribution in any one of claims 1 to 4.

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