Method for designing lightning shielding by using diverter strips on aircraft, system, device, and medium

Abstract

Disclosed are a method for designing lightning shielding by using diverter strips on an aircraft, a system, a device, and a medium. The method comprises: determining boundary conditions of a simulation space; according to the boundary conditions of the simulation space, performing numerical calculation on an electric field in the simulation space; according to the calculation result of the electric field and in combination with fractal theory, determining a probability of the direction of lightning leader development, and, according to the probability of the direction of lightning leader development, randomly selecting a subsequent development position of a lightning downward-moving stepped leader; determining, on the basis of testing and simulation results of a corona discharge characteristic at the tip of a metal electrode having a small radius of curvature, whether an initial corona at an end portion of a diverter strip has been initiated, and determining whether an initial corona at an end portion of a diverter strip has been initiated; determining whether the lightning downward-moving stepped leader can, after attaching to an insulating plate, run through a gap along the surface and reach an adjacent diverter strip; repeating the process above, and performing multiple simulations to solve the probability of lightning protection of diverter strips and establish a relationship between the probability of lightning protection of diverter strips and the distance between the diverter strips at different thicknesses of and using different materials for the insulating plate.

Description

A method, system, device and medium for designing lightning shielding of aircraft guide strips Technical Field

[0001] The present invention belongs to the technical field of engineering lightning protection, and in particular relates to a design method, system, equipment and medium for lightning shielding of an aircraft guide strip. Background Art

[0002] Lightning is a high-energy atmospheric discharge characterized by high voltage amplitude, high current intensity, and strong destructive power. The voltage at the attachment point of a direct lightning strike is on the order of 108V, and the average lightning current can reach 3×104A. Lightning activity within the Earth's atmosphere is frequent, with up to 45,000 thunderstorms per day. Aircraft operating in the atmosphere are inevitably exposed to harsh lightning environments. Direct lightning effects, a typical form of lightning damage, are particularly susceptible to damaging sharp components such as aircraft antennas and radomes. This not only hinders the normal operation of air transport systems but also poses a severe challenge to the electromagnetic compatibility of military flight equipment such as solid rockets and missiles.

[0003] Modern high-speed aircraft commonly use composite skins as a surface material to replace traditional metal shells, striving for lightweight and heat-resistant performance. However, due to the non-conductivity of composite materials, when a lightning leader attaches to the surface, the high structural voltage at the attachment point can easily break through the skin, causing structural damage or internal system ablation, resulting in property damage and casualties. Modern aircraft often use strips of metal guide strips laid on the composite surface of the aircraft to drain and discharge lightning. Analyzing the attachment behavior of lightning leaders to the aircraft during the final jump phase and predicting the distribution of attachment points on the surface of the aircraft equipped with guide strips, thereby implementing targeted lightning shielding designs for the aircraft, has become the key to the safe operation of modern aircraft.

[0004] For aircraft made of composite materials, guide bar protection technology is a key method for protecting against direct lightning strikes. Guide bar protection involves attaching a certain number of metal guide structures to the aircraft's skin. When lightning approaches the aircraft's surface, the metal guide bars distort the spatial electric field, attracting the lightning leader, thereby discharging the lightning current or lowering the flashover threshold, significantly reducing damage to the aircraft from direct lightning strikes. Guide bar protection technology has been widely used in lightning-vulnerable components such as fairings and wings. However, current research on the principles of guide bar protection, particularly the quantitative design of guide bar spacing, is insufficient. Existing design methods determine guide bar placement based on an empirical relationship between the voltage drop between the guide bar and the leader head. This fails to reflect vulnerable areas and makes it difficult to quantitatively assess overall lightning shielding effectiveness. Given the random, fractal nature of lightning leader development, the distribution of its attachment points on the aircraft surface is also random, hindering the determination of the optimal guide bar placement. To this end, it is necessary to theoretically analyze the attachment characteristics of lightning leaders in the terminal jump stage, study the distribution law of their attachment points on the aircraft skin under specific geometry and specific guide strip arrangements, and improve the aircraft's direct lightning protection performance.

[0005] Furthermore, while some researchers have proposed engineering solutions for optimizing guide bar layout and lightning shielding performance, they haven't established a link between protection probability and external factors, hindering design redundancy. Excessively large guide bar spacing, while beneficial for aircraft lightweighting and economy, can compromise protection performance. Conversely, excessive spacing can lead to redundant protection and impact aircraft energy consumption. Existing standards such as SAE ARP5412 and SAE ARP5416 recommend the use of a pilot attachment test method for guide bar design, but these methods require long test cycles, are costly, and lack universal applicability. Therefore, research is needed to characterize the probability distribution of lightning attachment points during the final jump phase of an aircraft, develop a design method for lightning shielding using aircraft guide bars, and guide lightning protection design for aircraft.

[0006] Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a method and system for controlling the side plates of overflow brick lead-out amount. The method adjusts the width of the glass substrate lead plate and the actual overflow coefficient so that the thickness of the side plates during the glass substrate forming process can meet the requirements; thereby solving the problem of lead plate fluctuation caused by the thin thickness of the side plates during the glass substrate forming process after the lead-out amount is increased.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The purpose of the present invention is to provide a lightning shielding design method, system, equipment and medium for aircraft guide strips to solve the problems existing in the prior art. The present invention can simulate the attachment of direct lightning strikes to a given composite guide strip structure, consider the oncoming leader initiation mechanism and the surface flashover mechanism, calculate the probability distribution of lightning attachment, and provide the lightning protection probability of the aircraft guide strip.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A lightning shielding design method for an aircraft guide strip, comprising:

[0012] Step 1: Set up a typical conductor plate-insulator plate-guide bar structure simulation scenario, initialize the simulation space size based on the typical conductor plate-insulator plate-guide bar structure, discretize the simulation space and guide bar structure, and determine the simulation space boundary conditions;

[0013] Step 2: Based on the boundary conditions of the simulation space, the electric field in the simulation space is numerically calculated using the finite difference method combined with the super-relaxation iteration method. Based on the electric field calculation results and combined with fractal theory, the directional probability of the lightning leader's development is determined, and the subsequent development position of the lightning leader in the downward cascade is randomly selected according to the directional probability;

[0014] Step 3: Based on the experimental and simulation results of the corona discharge characteristics of the tip of the metal electrode with a small curvature radius, determine whether the initial corona at the end of the guide bar has started. If not, the lightning downward step leader in step 2 continues to develop one step, and continue to determine whether the initial corona at the end of the guide bar has started. If the initial corona has started, then based on the streamer theory and combined with the spatial electric field calculation results, calculate whether the oncoming streamer discharge on the axis of the end of the guide bar has started. If the oncoming streamer discharge has started, determine the development process of the oncoming streamer according to the fractal theory and directional probability described in step 2. If not, the lightning downward step leader in step 2 continues to develop one step, and continue to determine whether the oncoming streamer discharge on the axis of the end of the guide bar has started.

[0015] Step 4: If the downward-step leader of the lightning strike contacts the oncoming streamer discharge, the guide strips provide direct lightning protection. If the downward-step leader of the lightning strike develops to the insulating plate, there is a possibility of surface flashover from the attachment position to the adjacent guide strips. Based on the leader development model, a surface flashover criterion for impact on the insulating plate surface is established to determine whether the downward-step leader can penetrate the surface gap to the adjacent guide strips after attaching to the insulating plate.

[0016] Step 5: Based on the Monte Carlo method, repeat steps 1 to 4 multiple times to calculate the lightning protection probability of the guide strips and establish the relationship between the lightning protection probability of the guide strips and the guide strip spacing under different insulation board thicknesses and materials.

[0017] Furthermore, the calculation scenario and boundary conditions in step 1 are specifically as follows:

[0018] The simulation scenario for the conductor plate-insulator plate-guide bar structure consists of a double-layer conductor plate-insulator plate structure with a side length of 1 meter, with guide bars distributed across it. Both the conductor plate and guide bars are grounded. The initial downward-moving step leader is 0.2 meters long and located on the centerline of the gap, 1 meter above the insulating plate. The simulation space is a two-dimensional plane, 1.5 meters wide and 1.2 meters high. The potential boundary conditions of the initial downward-moving step leader are determined by the instantaneous value of the applied -1200 kV voltage waveform D, while the surrounding boundary conditions are determined by the electrostatic field simulation results under the instantaneous voltage of the initial downward-moving step leader.

[0019] Furthermore, the numerical calculation method of the spatial electric field in step 2 is as follows:

[0020] Outside the boundaries of the leader and the guide strip, since there is no space charge, the distribution of space potential satisfies the Laplace equation:

[0021] in, refers to the potential in the simulation space, Δ is the Laplace operator;

[0022] According to the set grid scale, the simulation space is divided into squares with a side length of L. Only the field quantities at the grid points are considered, and Equation (1) is discretized as:

[0023] Where: superscript n is the nth iteration; is the potential at the spatial coordinate (x, y) after n iterations; are the potentials around the point respectively;

[0024] Since the simple iterative method has a slow convergence speed and takes a long time, the super-relaxation iterative method is used to calculate the potential distribution. The iterative formula can be changed to:

[0025] Where: w is the relaxation factor, which ranges from 1 to 2;

[0026] Initialize an iteration accuracy ε, and stop the calculation when the potential calculation result at any position in the simulation space differs from the result of the nth iteration by no more than ε after the n+1th iteration.

[0027] Furthermore, in the initial corona initiation determination in step three, referring to the experimental and simulation results on the corona discharge characteristics of the tip of the metal electrode with a small curvature radius, it is believed that the initial electric field intensity of the corona discharge at the end of the guide bar is basically unrelated to the curvature radius of the guide bar end. The positive polarity initial corona starting electric field intensity is taken as 995kV / m, and the negative polarity corona starting electric field intensity is taken as 880kV / m.

[0028] The method for determining the onset of oncoming streamer discharge in step 3 is as follows:

[0029] Assume that the field strength inside the streamer is E S is a constant (500kV / m), according to the electric field E at the end axis of the guide bar at any time b and the external electric field E at the beginning of the initial corona b-i , calculate the initial corona space charge field E sp , and then calculate the local field strength E in the corona region after considering the space charge field at any time loc :

[0030] The local electric field E in the corona region is loc Determines the equivalent impact ionization coefficient on the discharge axis. According to streamer theory, if the line integral of the equivalent impact ionization coefficient along the axis of the local high field strength region is greater than the critical number of ions required to maintain a self-sustaining discharge, the streamer discharge can begin to develop:

[0031] Where E is the local electric field inside the corona region; α is the impact ionization coefficient, cm -1 ; η is the adhesion coefficient, cm -1 ; α-η is the equivalent collision ionization coefficient, x1 is the coordinate of the end of the guide bar; x2 is the coordinate where the equivalent collision ionization coefficient is zero (i.e., the coordinate where α = η); N stab is the critical ion number, about 0.55×10 8 .

[0032] Considering the humid atmosphere, the ionization coefficient and adhesion coefficient can be expressed as:

[0033] Where, P w is the water vapor pressure, Torr; P is the atmospheric pressure, Torr; the subscripts w and d represent wet and dry conditions, respectively. Under wet and dry conditions, the collision ionization coefficient and adhesion coefficient are expressed as: α w / P=0.001×(E / P) 2 -0.06×(E / P)+1 (19) α d / P=4.7786e -221×P / E (20) η d / P=0.87×10 -5 (E / P) 2 -0.54×10 -3 ×(E / P)+0.01298 (22)

[0034] The impact ionization coefficient increases rapidly with increasing electric field in the high field strength region. The adhesion coefficient changes slowly with field strength overall, and its value in the high field strength region is much smaller than the impact ionization coefficient. When the field strength is low, the ionization coefficient and the adhesion coefficient are close, and there is no obvious self-sustaining discharge. When the field strength is high, the ionization coefficient is much higher than the adhesion coefficient. At this time, along the discharge axis, impact ionization dominates, and the number of electrons increases exponentially. When the line integral of the equivalent ionization coefficient along the local high field strength region is greater than the critical number of electrons or positive ions (Equation (5)), it is considered that the streamer discharge can initiate.

[0035] The above-mentioned head-on discharge initiation determination is realized by MATLAB programming. During the main program simulation of the development of the gap streamer of the guide bar, the electric field intensity on the surface of the guide bar end is constantly monitored. If it reaches the initial corona initiation field, it is considered that the initial corona has started, and the external background electric field E at this time is recorded. b-i , otherwise return to the main program. When the initial corona starts, the auxiliary function is used to extract the electric field intensity distribution of the discharge axis just above the end of the corresponding guide bar, and the electric field intensity E inside the corona zone at the current moment after considering the space charge effect is calculated using formula (4) loc Distribution. Based on this axial field distribution, equations (6) to (10) are used to calculate the impact ionization coefficient and adhesion coefficient along the line. When the line integral of the equivalent impact ionization coefficient along the high field strength region exceeds the critical number of electrons or the critical number of positive ions, the streamer is considered to have started. Otherwise, the program returns to the main program to continue simulating the streamer development process.

[0036] Furthermore, the criterion for surface flashover of the insulating board in step 4 is specifically:

[0037] The surface development speed of the downward lightning leader after it attaches to the insulating plate is regarded as a function of the residual gap voltage and the average electric field strength of the residual gap:

[0038] Where, l is the surface leader length m; k is the velocity coefficient, m 2 / (kV 2 ·s); U is the voltage at the attachment point, kV; E l is the internal field strength of the leader, kV / m; d is the surface gap size, m; δ is the relative air density; E th is the streamer initiation threshold electric field strength, kV / m.

[0039] Based on the leader development speed shown in formula (11), combined with the voltage waveform at the attachment point, MATLAB programming is used to determine whether the surface discharge of the insulating plate can develop continuously. The time domain voltage waveform of the lightning attachment point is divided into a small time interval Δt, and the leader development speed and development length at the current moment are calculated under the condition that the residual gap electric field can maintain the leader development. When the development length exceeds 2 / 3 of the gap scale, it is considered that the surface discharge can penetrate the gap, and the voltage and corresponding time when the surface sliding flash penetrates are output; if the surface discharge length still does not reach the breakdown condition after the half-peak value of the impulse voltage, it is considered that the surface discharge cannot penetrate the gap, the sliding flash discharge cannot occur, and the insulation layer will be broken down. When the surface flashover can penetrate the gap, due to the competition process between the surface flashover and the dielectric breakdown, the final form of the discharge depends on the instantaneous value of the voltage at the attachment point at the end of the flashover jump and the dielectric strength of the dielectric. The breakdown voltage is compared with the dielectric strength of the medium. If the voltage at the attachment point when the flashover is completed exceeds the dielectric strength of the medium, it is considered that the dielectric breakdown occurs immediately; otherwise, it is considered that the dielectric breakdown will not occur, and surface flashover occurs at this time.

[0040] Furthermore, in step 5, the relationship between the comprehensive lightning protection probability of the guide strips and the guide strip spacing is obtained as follows:

[0041] The process of lightning leader attaching to the guide bar is simulated based on the Monte Carlo method. The probability of leader attaching to the guide bar and the insulating plate is obtained. The case where the leader directly attaches to the guide bar or attaches to the insulating plate and then flashes over to the guide bar is considered as successful protection. The relationship between the comprehensive lightning protection probability and the spacing of the guide bar under the conditions of different materials and thicknesses of insulating plates is fitted by a polynomial function. The comprehensive protection probability P is expressed as: P = f(D) (24)

[0042] Where D is the distance between the guide bars, cm.

[0043] An aircraft guide strip lightning shielding design system, comprising:

[0044] Setting module: used to set up a typical conductor plate-insulation plate-guide bar structure simulation scenario, initialize the simulation space size according to the typical conductor plate-insulation plate-guide bar structure, discretize the simulation space and guide bar structure, and determine the simulation space boundary conditions;

[0045] Calculation module: It is used to perform numerical calculations on the electric field in the simulation space based on the boundary conditions of the simulation space using finite differences combined with the super-relaxation iteration method. Based on the electric field calculation results and combined with fractal theory, the directional probability of the lightning leader's development is determined, and the subsequent development position of the lightning leader in the downward cascade is randomly selected according to the directional probability.

[0046] The first judgment module is used to judge whether the initial corona at the end of the guide bar has started based on the test and simulation results of the corona discharge characteristics of the tip of the metal electrode with a small curvature radius. If not, the lightning downward step leader in step 2 continues to develop one step, and it is continued to judge whether the initial corona at the end of the guide bar has started; if the initial corona has started, based on the streamer theory, combined with the electric field calculation results, it is calculated whether the oncoming streamer discharge on the axis of the end of the guide bar has started. If the oncoming streamer discharge has started, the development process of the oncoming streamer is determined according to the fractal theory and directional probability described in step 2. If not, the lightning downward step leader in step 2 continues to develop one step, and it is continued to judge whether the oncoming streamer discharge on the axis of the end of the guide bar has started;

[0047] The second judgment module: If the downward-stepped leader of the lightning strike contacts the oncoming streamer discharge, the guide strips provide direct lightning protection. If the downward-stepped leader of the lightning strike develops to the insulating plate, there is a possibility of surface flashover from the attachment position to the adjacent guide strips. Based on the leader development model, a surface flashover criterion for impact on the insulating plate surface is established to determine whether the downward-stepped leader of the lightning strike can penetrate the surface gap to the adjacent guide strips after attaching to the insulating plate.

[0048] Loop module: Used to repeat steps 1 to 4 based on the Monte Carlo method, multiple simulations to obtain the lightning protection probability of the guide strips and establish the relationship between the lightning protection probability of the guide strips and the guide strip spacing under different insulation board thicknesses and materials.

[0049] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for designing lightning shielding of an aircraft guide strip are implemented.

[0050] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for designing lightning shielding of an aircraft guide strip.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] This paper uses a conductor plate-insulating plate-guide bar structure as the basic simulation scenario, with lightning impulse voltage amplitude, guide bar spacing, insulation layer thickness, and insulation layer dielectric type as inputs. The finite difference method combined with a super-relaxation iterative format is used to calculate the simulated spatial electric field distribution. Based on this, the random development of the descending step leader and the initiation and development of the head-on discharge are calculated. The Monte Carlo method is then used to simulate the probability distribution characteristics of lightning attachment points on the aircraft surface during the final lightning jump. This paper considers the situation where the initial attachment point of lightning on the insulating plate causes surface flashover to the guide bar. The impact flashover criterion based on the leader development method is used to determine whether surface flashover can occur. The comprehensive lightning protection probability of the guide bar is calculated for different simulation scenarios, and this attachment probability provides guidance for the lightning protection design of aircraft guide bars. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0054] FIG1 is an attachment target structure in an embodiment;

[0055] Figure 2 shows the time domain waveform of the upper rod electrode boundary condition;

[0056] Figure 3 is a schematic diagram of the upper boundary interception method;

[0057] Figure 4 is a schematic diagram of the discretized grid of the computational domain;

[0058] FIG5 is a flow chart for determining surface sliding discharge;

[0059] Figure 6 shows the relationship between the comprehensive protection probability of the LDPE insulation layer guide strips and the guide strip spacing. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0061] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0062] Example 1

[0063] Step 1: Set up a typical conductor plate-insulator plate-guide bar structure simulation scenario, initialize the simulation space size according to the structure, discretize the simulation space and guide bar structure, and determine the simulation boundary conditions.

[0064] In this embodiment, the simulation space size is a two-dimensional plane with a height of 1.2m and a width of 1.5m. The attached target is a conductor plate-insulation plate-guide bar structure with a side length of 1m. The conductor plate is 5mm thick; the insulation plate is made of LDPE with thicknesses of 2mm and 3mm respectively; the guide bar is 1cm wide and 1mm thick. A total of 4 guide bars are set, 2 of which are located at the left and right edges of the insulation plate, and 2 are symmetrically placed on both sides of the gap axis with a distance of D (cm). The gap calculation scenario is shown in Figure 1. In terms of field boundary conditions, for the initial lightning downward step leader, a voltage waveform D is applied, which is defined as an operating impulse voltage with a wavefront time within 50-250μs (as shown in Figure 2), and the peak value is set to -1200kV. The time domain expression of the upper rod voltage is:

[0065] Among them, U p is the voltage peak, kV; t is the time, μs. The starting time t0 of the downstreamer-leader system is set to 30μs, and the potential boundary conditions of the upper rod electrode are changed in real time in the simulation using formula (25). The boundary conditions at the upper, lower, left, and right boundaries of the simulation area are determined as follows: it is assumed that the potential excitation of the upper rod electrode is linearly related to the boundary potential response. According to the instantaneous value of the potential of the upper rod electrode, combined with the fitting relationship between the boundary potential and the coordinates, the boundary potential distribution at any time is determined. Taking the upper boundary as an example, a two-dimensional finite element gap model consistent with the calculation scenario is established, and the potential of the upper rod electrode is set to -1000kV. After obtaining the potential distribution in the calculation domain, a section of the intercept is taken at the upper boundary as shown in Figure 3, and the potential distribution on the intercept is fitted with a cubic polynomial function, and the upper rod potential is normalized. The relationship between the normalized potential of the upper boundary and the distance from the gap axis is: U / Up =-0.361x 3 +1.108x 2 -1.476x+1.002 (26)

[0066] In the formula, U / U p is the normalized boundary potential; x is the distance from the gap axis, in cm. The determination method for the other boundary potentials is similar.

[0067] Step 2: According to the boundary conditions of the simulation space, the spatial electric field is numerically calculated using the finite difference method combined with the super-relaxation iterative method. Based on the electric field calculation results and combined with the fractal theory, the directional probability of the lightning leader development is determined, and the subsequent development position of the lightning downward step leader is randomly selected according to the probability.

[0068] In this embodiment, the computational domain is discretized with a grid size of 0.1 mm. The discretized computational domain is shown in Figure 4. Except for the grid points (boundary conditions) with the potential determined above, the initial potential of the remaining grid points is 0. The spatial potential distribution is calculated by combining super-relaxation iteration. The iterative formula is:

[0069] Where w is the relaxation factor, which is taken as 1.95; the superscripts n and n+1 represent the number of iterations; and L represents the grid size.

[0070] When the n+1th iteration meets the accuracy requirement, the iteration is stopped. After obtaining the potential at any grid point, the probability of the development direction of the downstreamer-leader system is determined according to the WZ model:

[0071] Where, P mn is the probability of the direction from the developed point m to the point to be developed n; E mn is the average field strength from the developed point to the point to be developed, kV / m; E th is the discharge threshold field strength, which is 75 kV / m; η is the development probability index, which is 8; N d is the total number of currently developed points; N c is the total number of points to be developed at present. The location of the next leader development point is determined by probability, and the leader development is completed. Then the boundary conditions are updated and the spatial electric field is calculated again. This process is repeated until the leader is finally attached.

[0072] Step 3: Based on the experimental and simulation results of the corona discharge characteristics of the tip of the metal electrode with a small curvature radius, determine whether the initial corona at the end of the guide bar has started. If not, the downward step leader of the lightning in step 2 continues to develop one step, and continue to determine whether the initial corona at the end of the guide bar has started; if the initial corona has started, then based on the streamer theory, combined with the electric field calculation results, calculate whether the oncoming streamer discharge on the axis of the guide bar end has started. If the oncoming streamer discharge has started, determine the development process of the oncoming streamer according to the fractal theory and directional probability described in step 2. If not, the downward step leader of the lightning in step 2 continues to develop one step, and continue to determine whether the oncoming streamer discharge on the axis of the guide bar end has started.

[0073] In this implementation, the results of spatial electric field calculations are used to determine whether the electric field at the ends of the guide strips has reached the initial corona initiation condition. Initial corona initiation is considered to occur when the average electric field strength between the grid point at the end of the guide strip and the adjacent grid point directly above it reaches 995 kV / m. After the initial corona initiation, the electric field strength distribution along the axis of the guide strip end is calculated. Taking into account humid atmospheric conditions, the impact ionization coefficient and adhesion coefficient along the axis are calculated:

[0074] Where α is the collision ionization coefficient, cm -1 ; η is the adhesion coefficient, cm -1 ;P w is the water vapor pressure, Torr; P is the atmospheric pressure, Torr; the subscripts w and d indicate wet and dry conditions, respectively. After obtaining the impact ionization coefficient and adhesion coefficient along the axis of the guide strip end, the following formula is used to determine whether the headstream has started:

[0075] Where x1 represents the streamer end coordinate, x2 represents the coordinate where the collision ionization coefficient is equal to the adhesion coefficient, and N stab is the critical number of positive ions.

[0076] Step 4: If the downward-stepped leader of the lightning strike contacts the oncoming streamer discharge, the guide strips provide direct lightning protection. If the downward-stepped leader of the lightning strike develops to the insulating plate, there is a possibility of surface flashover from the attachment position to the adjacent guide strips. Based on the leader development model, a surface flashover criterion for impact on the insulating plate surface is established to determine whether the downward-stepped leader of the lightning strike can penetrate the surface gap to the adjacent guide strips after attaching to the insulating plate.

[0077] In this embodiment, according to the leader development model, after the streamer penetrates the surface gap, the main discharge development characteristics are described by the leader development speed. The leader development speed is a function of the applied voltage and the remaining gap length, expressed as:

[0078] Where, l is the length of the leader along the surface in m; k is the velocity coefficient, which is 1×10 -6 m 2 / (kV 2 ·s); U is the voltage at the attachment point, kV, which is calculated in real time based on the upper rod boundary conditions and the pilot voltage drop; E l is the internal field strength of the pilot, which is 500 kV / m; d is the surface gap size, m; δ is the relative air density, which is 0.9292; E th is the threshold electric field strength of surface streamer, which is taken as 250kV / m.

[0079] Using a time interval of Δt = 0.008 μs as the time step for creeping discharge determination, the leader development speed and length at the current moment are calculated, provided that the residual gap electric field can sustain leader development. When the development length exceeds 2 / 3 of the gap size, the creeping discharge is considered to have penetrated the gap, and the voltage and corresponding time at which the creeping discharge penetrates the gap are output. If the creeping discharge length still does not reach the breakdown condition after the half-peak value of the impulse voltage, the creeping discharge is considered to have failed to penetrate the gap, and the sliding discharge cannot occur. At this point, the insulation layer will be broken down. The entire determination process is shown in Figure 5.

[0080] Step 5: Based on the Monte Carlo method, multiple simulations are performed to obtain the lightning protection probability of the guide strips, and the relationship between the guide strip protection probability and the guide strip spacing under different insulation board thicknesses and materials is established.

[0081] In this embodiment, 200 simulations were performed for LDPE insulation board at different guide bar spacings. The attachment frequency was used instead of the attachment probability to obtain the comprehensive protection probability of the guide bars at different spacings, as shown in Figure 6. The protection probability was fitted with a polynomial function, and the relationship between the comprehensive protection probability of the four-guide bar structure and the spacing under the conditions of 2 and 3 mm LDPE insulation board was obtained as follows: P = -7×10 -4 D 4 +0.055D 3 -1.549D 2 +18.756D+14.363 (32) P=-4.296×10 -4 D 4 +0.0358D 3 -1.084D 2 +14.253+29.1508 (33)

[0082] Therefore, through the aircraft guide bar lightning shielding design method of the present invention, the attachment process of the lightning leader to the guide bar under different insulation layer materials and different guide bar arrangements can be effectively simulated, the attachment probability distribution and the comprehensive protection probability of the guide bar can be analyzed, and guidance can be provided for the actual aircraft lightning protection design.

[0083] Example 2

[0084] An aircraft guide strip lightning shielding design system, comprising:

[0085] Setting module: used to set up a typical conductor plate-insulation plate-guide bar structure simulation scenario, initialize the simulation space size according to the typical conductor plate-insulation plate-guide bar structure, discretize the simulation space and guide bar structure, and determine the simulation space boundary conditions;

[0086] Calculation module: It is used to perform numerical calculations on the electric field in the simulation space based on the boundary conditions of the simulation space using finite differences combined with the super-relaxation iteration method. Based on the electric field calculation results and combined with fractal theory, the directional probability of the lightning leader's development is determined, and the subsequent development position of the lightning leader in the downward cascade is randomly selected according to the directional probability.

[0087] The first judgment module is used to judge whether the initial corona at the end of the guide bar has started based on the test and simulation results of the corona discharge characteristics of the tip of the metal electrode with a small curvature radius. If not, the lightning downward step leader in step 2 continues to develop one step, and it is continued to judge whether the initial corona at the end of the guide bar has started; if the initial corona has started, based on the streamer theory, combined with the electric field calculation results, it is calculated whether the oncoming streamer discharge on the axis of the end of the guide bar has started. If the oncoming streamer discharge has started, the development process of the oncoming streamer is determined according to the fractal theory and directional probability described in step 2. If not, the lightning downward step leader in step 2 continues to develop one step, and it is continued to judge whether the oncoming streamer discharge on the axis of the end of the guide bar has started;

[0088] The second judgment module: If the downward-stepped leader of the lightning strike contacts the oncoming streamer discharge, the guide strips provide direct lightning protection. If the downward-stepped leader of the lightning strike develops to the insulating plate, there is a possibility of surface flashover from the attachment position to the adjacent guide strips. Based on the leader development model, a surface flashover criterion for impact on the insulating plate surface is established to determine whether the downward-stepped leader of the lightning strike can penetrate the surface gap to the adjacent guide strips after attaching to the insulating plate.

[0089] Loop module: Used to perform multiple simulations based on the Monte Carlo method to obtain the lightning protection probability of the guide strips and establish the relationship between the lightning protection probability of the guide strips and the guide strip spacing under different insulation board thicknesses and materials.

[0090] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0091] The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0092] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0093] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art may still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A method for designing lightning shielding of aircraft guide strips, characterized in that: include: Step 1: Set up a typical conductor plate-insulation plate-guide bar structure simulation scene, initialize the simulation space size according to the typical conductor plate-insulation plate-guide bar structure, discretize the simulation space and the guide bar structure, and determine the simulation space boundary conditions; Step 2: According to the boundary conditions of the simulation space, the electric field in the simulation space is numerically calculated using the finite difference combined with the super-relaxation iteration method. Based on the electric field calculation results and combined with the fractal theory, the direction probability of the lightning leader development is determined, and the subsequent development position of the lightning down-step leader is randomly selected according to the direction probability; Step 3: Based on the test and simulation results of the corona discharge characteristics of the tip of the metal electrode with a small curvature radius, determine whether the initial corona at the end of the guide bar has started. If not, the lightning downward step leader in step 2 continues to develop one step, and continue to determine whether the initial corona at the end of the guide bar has started; if the initial corona has started, then based on the streamer theory, combined with the electric field calculation results, calculate whether the oncoming streamer discharge on the axis of the end of the guide bar has started. If the oncoming streamer discharge has started, determine the development process of the oncoming streamer according to the fractal theory and directional probability described in step 2. If not, the lightning downward step leader in step 2 continues to develop one step, and continue to determine whether the oncoming streamer discharge on the axis of the end of the guide bar has started; Step 4: If the downward step leader of lightning contacts the oncoming streamer discharge, the guide strip completes the direct lightning protection; if the downward step leader of lightning develops to the insulating plate, there is a possibility of surface flashover from the attachment position to the adjacent guide strip, then based on the leader development model, the surface flashover criterion of the insulating plate surface impact is established to determine whether the downward step leader of lightning can penetrate the surface gap to the adjacent guide strip after attaching to the insulating plate; Step 5: Based on the Monte Carlo method, repeat steps 1 to 4, perform multiple simulations to obtain the lightning protection probability of the guide strip, and establish the relationship between the lightning protection probability of the guide strip and the guide strip spacing under different insulation board thicknesses and materials.

2. The method for designing lightning shielding of an aircraft guide strip according to claim 1, characterized in that: The step 1 is specifically as follows: The simulation scenario of the conductor plate-insulation plate-guide bar structure is a double-layer structure of a conductor plate-insulation plate with a side length of 1 meter. The upper distribution guide bar, the conductor plate and the guide bar are grounded, the initial lightning downward step leader is 0.2m long, located on the central axis of the gap, and 1 meter above the insulating plate; the simulation space is a two-dimensional plane, 1.5m wide and 1.2m high; the potential boundary conditions of the initial lightning downward step leader are determined by the instantaneous value of the applied -1200kV voltage waveform D, and the surrounding boundary conditions are determined by the electrostatic field simulation results under the instantaneous voltage of the initial lightning downward step leader.

3. The method for designing lightning shielding of an aircraft guide strip according to claim 1, characterized in that: The numerical calculation method of the spatial electric field in step 2 is as follows: Outside the boundaries of the pilot and guide strips, since there is no space charge, the distribution of space potential satisfies the Laplace equation: in, refers to the potential in the simulation space, Δ is the Laplace operator; According to the set grid scale, the simulation space is divided into square grids with a side length of L. Only the field quantities at the grid points are considered, and equation (1) is discretized as: Where: superscript n is the nth iteration; is the potential at the spatial coordinate (x, y) after n iterations; are the potentials around the point respectively; The super-relaxation iteration method is used to calculate the potential distribution, and the iteration formula is changed to: Where: w is the relaxation factor; When after the n+1th iteration, the potential calculation result at any position in the simulation space differs from the result of the nth iteration by no more than ε, the calculation is stopped, where ε is the iteration accuracy.

4. The method for designing lightning shielding of an aircraft guide strip according to claim 1, characterized in that: In the initial corona start judgment in step 3, based on the test and simulation results on the corona discharge characteristics of the tip of the metal electrode with a small curvature radius, the corona discharge start electric field strength at the end of the guide bar is independent of the curvature radius of the end of the guide bar. The positive polarity initial corona start electric field strength is taken as 995kV / m, and the negative polarity initial corona start electric field strength is taken as 880kV / m. The method for determining the onset of oncoming streamer discharge in step 3 is as follows: Assume that the internal field strength of the streamer is E S is a constant, according to the electric field E at the end axis of the guide bar at any time b and the external electric field E at the beginning of the initial corona b-i , find the initial corona space charge field E sp , and then calculate the local field strength E in the corona region after considering the space charge field at any time loc : The local electric field E in the corona region is loc Determine the equivalent impact ionization coefficient on the discharge axis. According to the streamer theory, if the line integral of the equivalent impact ionization coefficient along the axis of the local high field strength region is greater than the critical number of ions required to maintain a self-sustaining discharge, the streamer discharge can begin to develop: Where E is the local electric field inside the corona region; α is the impact ionization coefficient, cm -1 ; η is the adhesion coefficient, cm -1 ; α-η is the equivalent collision ionization coefficient, x1 is the coordinate of the end of the guide bar; x2 is the coordinate where the equivalent collision ionization coefficient is zero, that is, the coordinate where α=η; N stab is the critical ion number; Considering the humid atmosphere, the collision ionization coefficient and adhesion coefficient are expressed as: Where P w is the water vapor pressure, Torr; P is the atmospheric pressure, Torr; the subscripts w and d represent the wet condition and the dry condition, respectively. Under the wet condition and the dry condition, the collision ionization coefficient and the adhesion coefficient are expressed as follows: α w / P=0.001×(E / P) 2 −0.06×(E / P)+1 (7) a d / P=4.7786e -221×P / E (8) η d / P=0.87×10 -5 (E / P) 2 −0.54 × 10 -3 ×(E / P)+0.01298 (10) When the line integral of the equivalent impact ionization coefficient along the local high field strength region is greater than the critical number of electrons or positive ions, it is considered that the streamer discharge can be initiated. The equivalent impact ionization coefficient is the product of the impact ionization coefficient and the attachment coefficient. The difference in numbers.

5. The method for designing lightning shielding of aircraft guide strips according to claim 4, characterized in that: MATLAB programming is used to realize the determination of the onset of head-on discharge. During the main program simulation of the development of the gap streamer of the guide bar, the electric field intensity on the surface of the end of the guide bar is monitored at all times. If it reaches the initial corona starting field, it is considered that the initial corona has started, and the external background electric field E at this time is recorded. b-i Otherwise, return to the main program. When the initial corona starts, extract the electric field intensity distribution of the discharge axis just above the end of the corresponding guide bar, and use formula (4) to calculate the field intensity E inside the corona zone at the current moment after considering the space charge effect. loc Distribution, according to this axial field distribution, use equations (6) to (10) to calculate the collision ionization coefficient and adhesion coefficient along the line. When the line integral of the equivalent collision ionization coefficient along the high field strength area exceeds the critical number of electrons or the critical number of positive ions, the streamer is considered to have started. Otherwise, return to the main program to continue the simulation of the streamer development process.

6. The method for designing lightning shielding of an aircraft guide strip according to claim 1, characterized in that: The criterion for the surface flashover of the insulating board in step 4 is as follows: After the lightning downward step leader is attached to the insulating plate, it continues to develop along the surface gap to the adjacent guide strip. The surface development speed of the lightning downward step leader is regarded as a function of the residual gap voltage and the residual gap average electric field strength: Where l is the pilot length in the surface gap, m; k is the velocity coefficient, m 2 / (kV 2 ·s); U is the voltage at the attachment point, kV; E l is the internal field strength of the leader, kV / m; d is the gap size along the surface, m; δ is the relative air density; E th is the streamer onset threshold electric field strength, kV / m; According to the leader development speed shown in formula (11), combined with the voltage waveform at the attachment point, MATLAB programming is used to determine whether the surface discharge of the insulating plate can develop continuously. The time domain voltage waveform of the lightning attachment point is divided by the time interval Δt, and the leader development speed and development length at the current moment are calculated under the condition that the residual gap electric field can maintain the leader development. When the development length exceeds 2 / 3 of the gap scale, it is considered that the surface discharge can penetrate the gap, and the voltage and corresponding time when the surface sliding flash penetrates are output; if the surface discharge length still does not reach the breakdown condition after the half-peak value of the impulse voltage, it is considered that the surface discharge cannot penetrate the gap, and the sliding flash discharge Electricity cannot occur, and the insulation layer will be broken down at this time; when surface flashover can penetrate the gap, the breakdown voltage is compared with the insulation strength of the medium. If the voltage at the attachment point when the flashover is completed has exceeded the insulation strength of the medium, it is considered that the dielectric breakdown occurs immediately; otherwise, it is considered that the dielectric breakdown will not occur, and surface flashover occurs at this time.

7. The method for designing lightning shielding of aircraft guide strips according to claim 1, characterized in that: The relationship between the lightning protection probability of the guide strip and the guide strip spacing in step 5 is obtained as follows: The attachment process of the lightning leader to the guide bar is simulated based on the Monte Carlo method, and the probability of the leader attaching to the guide bar and the insulating board is obtained. The situation where the lightning leader directly attaches to the guide bar or attaches to the insulating board and then flashes to the guide bar along the surface is considered as successful protection. The relationship between the comprehensive lightning protection probability and the spacing of the guide bar under the conditions of different materials and thicknesses of insulating boards is fitted by a polynomial function, and the comprehensive protection probability P is expressed as: P=f(D) (12) Where D is the distance between guide bars, cm.

8. An aircraft guide strip lightning shielding design system, characterized in that: include: Setting module: used to set up a typical conductor plate-insulation plate-guide bar structure simulation scene, initialize the simulation space size according to the typical conductor plate-insulation plate-guide bar structure, discretize the simulation space and guide bar structure, and determine the simulation space boundary conditions; Calculation module: It is used to perform numerical calculation of the electric field in the simulation space according to the boundary conditions of the simulation space by using finite difference combined with super-relaxation iteration method. Based on the calculation results of the electric field and combined with fractal theory, the direction probability of the development of the lightning leader is determined, and the subsequent development position of the lightning down-step leader is randomly selected according to the direction probability. The first judgment module is used to judge whether the initial corona at the end of the guide bar has started based on the test and simulation results of the corona discharge characteristics of the tip of the metal electrode with a small curvature radius. If not, the lightning down-step leader in step 2 continues to develop one step, and continues to judge whether the initial corona at the end of the guide bar has started; if the initial corona has started, the oncoming corona on the axis of the end of the guide bar is calculated based on the streamer theory and combined with the electric field calculation results. Whether the streamer discharge has started. If the oncoming streamer discharge has started, the development process of the oncoming streamer is determined according to the fractal theory and directional probability described in step 2. If not, the lightning down-step leader in step 2 continues to develop one step, and continues to determine whether the oncoming streamer discharge on the axis of the end of the guide bar has started; The second judgment module: if the downward step leader of lightning contacts the oncoming streamer discharge, the guide strip completes the direct lightning protection; if the downward step leader of lightning develops to the insulating plate, there is a possibility of surface flashover from the attachment position to the adjacent guide strip, then based on the leader development model, the surface flashover criterion of the insulating plate surface impact is established to judge whether the downward step leader of lightning can penetrate the surface gap to the adjacent guide strip after attaching to the insulating plate; Loop module: It is used to perform multiple simulations based on the Monte Carlo method to obtain the lightning protection probability of the guide strip, and to establish the relationship between the lightning protection probability of the guide strip and the guide strip spacing under different insulation board thicknesses and materials.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for designing lightning shielding of an aircraft guide strip as claimed in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a method for designing lightning shielding of an aircraft guide strip are implemented as claimed in any one of claims 1 to 7.

Images