Method for determining the scale of a test aircraft for lightning zoning of an aircraft
By simplifying the aircraft model into a simplified curved surface and conducting lightning attachment point experiments, the problems of high difficulty and high cost in manufacturing scaled-down models were solved, and the conformity of scaled-down test results could be quickly determined.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-04-19
- Publication Date
- 2026-03-24
AI Technical Summary
In existing technologies, the manufacturing of scaled-down models for aircraft lightning zoning tests is difficult, costly, and time-consuming, and it is also difficult to quickly determine the conformity between the scaled-down test results and the actual initial attachment points of lightning on the aircraft.
By establishing a three-dimensional coordinate system for the aircraft, the aircraft model was simplified into a simplified curved surface. A scaled-down model was fabricated using a cuboid high-density rigid foam board, and lightning attachment point experiments were conducted. The attachment point probabilities were recorded and analyzed to determine the optimal scale ratio.
It simplifies the manufacturing difficulty and cost of scaled-down aircraft models, shortens the manufacturing cycle, and provides a method for quickly determining the conformity between scaled-down test results and the initial lightning attachment points of real aircraft.
Smart Images
Figure CN116039944B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of aircraft lightning zoning test, in particular to a method for determining the scale ratio of an aircraft lightning zoning test. BACKGROUND
[0002] Aircrafts are inevitably subjected to lightning environment, and lightning accidents caused by lightning strikes seriously affect the safety of aircrafts, so lightning protection design of aircrafts is particularly important. The division of lightning attachment area is the first step and a crucial step for the lightning protection design of aircrafts, and is the prerequisite for determining the subsequent lightning protection design scheme. Lightning zoning test is a necessary method for dividing lightning attachment area. In the aircraft zoning test method, the full-size lightning zoning test arrangement in the existing standard is based on a 50m strike method, that is, the distance between the high-voltage electrode and the nearest aircraft surface is at least 50m. Since there is no high-voltage test capability to break down a 50m air gap at home and abroad, the 50m air gap and the aircraft are proportionally reduced to carry out a scale test. The original electromagnetic compatibility design manual of the US Army suggests that the scale ratio should not be less than 1 / 30. Some scholars believe that when the scale ratio is in the range of 1 / 40-1 / 20, the test results are acceptable. However, it is found in a large number of tests that the scale ratio will have a significant impact on the results of lightning zoning test. However, due to the difficulty in manufacturing aircraft scale models, high processing cost, long manufacturing cycle, and the fact that it is not practical to make comparative tests on different scale models, and it is time-consuming and laborious to collect data and make comparisons according to the test method specified in the standard, it is not feasible. Therefore, how to determine the appropriate scale ratio and how to judge the conformity of the lightning zoning test results obtained in a specific scale test with the results of the real aircraft lightning initial attachment point have become the difficulties of this test technology. SUMMARY
[0003] The present application provides a method for determining the scale ratio of an aircraft lightning zoning test to accurately determine the appropriate scale ratio and provide favorable support for quickly judging the conformity of the lightning zoning test results obtained in a specific scale test with the results of the real aircraft lightning initial attachment point.
[0004] To achieve the above purpose, the technical scheme of the present application is as follows:
[0005] The method for determining the scale ratio of an aircraft lightning zoning test according to the present application is characterized in that the following steps are performed:
[0006] Step 1: Obtain a three-dimensional aircraft model for aircraft lightning partition test, and take the center of gravity of the three-dimensional aircraft model as the origin o, take the heading direction of the three-dimensional aircraft model as the y-axis, take the direction perpendicular to the y-axis as the z-axis, and take the direction from the belly to the back as the positive direction of the z-axis; the y-axis and the z-axis are both on the symmetry plane of the aircraft, and the x-axis is determined by the right-hand rule; thereby establishing an aircraft three-dimensional coordinate system o-xyz;
[0007] Step 2: Define that the three-dimensional aircraft model has max maximum points of aircraft surfaces, define the current maximum point as the nth point, and initialize n=1;
[0008] Step 3: Starting from the nth point, keep the surfaces with positive z-axis components of surface normals in order from top to bottom until the surface normal is perpendicular to the z-axis; obtain the nth continuous curve profile;
[0009] Step 4: Extend a surface in the downward direction of the z-axis of the nth continuous curve profile; if the extended nth surface intersects with other surfaces of the aircraft, stop extending and keep the extended nth surface, otherwise continue extending until the lowest point of the aircraft is reached, thereby obtaining the extended nth surface;
[0010] Step 5: Start from the second highest point of the z-axis of the three-dimensional aircraft model, take the second highest point as the n+1th point, assign n+1 to n, and return to step 3-5 to process until n=max, thereby obtaining max surfaces and forming a simplified surface;
[0011] Step 6: Define a variable m and initialize m=0; select a ratio i=1 / (25+m); scale the simplified surface according to the ith ratio to obtain a scaled surface;
[0012] Step 7: Use a cuboid high-density hard foam board as a processing substrate and process it according to the scaled surface, thereby obtaining an ith scaled aircraft simplified model;
[0013] Step 8: Lay aluminum foil or spray conductive paint on the upper surface of the aircraft simplified model, and keep the rest of the foam surface;
[0014] Step 9: Assign m+1 to m, and repeat steps 6-8 to process aircraft simplified models of different ratios i;
[0015] Step 10: Select an aircraft simplified model scaled by i for lightning attachment point test, and record the lightning attachment points:
[0016] Step 10.1: Place the scaled model of the airplane with scale ratio i directly below the rod electrode and directly above the ground plate;
[0017] Step 10.2: Fix the scaled model of the airplane with scale ratio i with one end of the insulator, and fix the ground plate on the other end of the insulator; after fixing, the posture of the scaled model of the airplane is in the state of airplane level flight, and the distance between any point on the scaled model of the airplane and the rod electrode is greater than 50 / i meters, and the distance between the scaled model of the airplane and the ground plate is greater than the maximum dimension length of the scaled model of the airplane;
[0018] Step 10.3: Apply a positive polarity lightning voltage C wave to the rod electrode, and record the position of the lightning arc entering the scaled model of the airplane, i.e. the lightning attachment point;
[0019] Step 10.4: Continuously carry out k tests according to step 10.3, and k is not less than 10;
[0020] Step 10.5: Test the scaled models of the airplane with different scale ratios i according to the process of step 10, and record the lightning attachment points;
[0021] Step 10.6: In the test of the scaled model of the airplane with scale ratio i, the number of lightning attachment points belonging to the back of the airplane and the vertical tail in k tests is extracted, and is recorded as l i机背 and l i垂尾 respectively; and the attachment probabilities P i机背 =l i机背 / k and P i垂尾 =l i机背 / k are calculated;
[0022] Step 10.6: If P i机背 =P i垂尾 , it means that k tests with scale ratio i meet the requirements, and the corresponding scale ratio i is taken as the scale ratio of the lightning zoning test;
[0023] If P i机背 >P i垂尾 , and P i / (i+1)机背 <P i / (i+1)垂尾 , take (iB-(i / (1+i))A) / (B-A) as the scale ratio of the lightning zoning test, A and B represent intermediate variables, and A=P i垂尾 -P i机背 ; B=P i / (i+1)垂尾 -P i / (i+1)机背 .
[0024] Compared with the prior art, the beneficial effects of the present application are embodied in:
[0025] The method of the present application greatly simplifies the manufacturing difficulty of the aircraft scale model, greatly shortens the manufacturing period, reduces the processing cost, and makes it possible to process different scale models; meanwhile, the present application proposes a method for judging the conformity of the lightning zoning test results under different scale conditions with the results of the actual aircraft lightning initial attachment point through the attachment point distribution law of the aircraft in a single flight attitude, so as to determine the optimal scale ratio of the scale model used in the lightning zoning test. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 is a flow chart for determining the optimal scale ratio of the scale model used in the aircraft lightning zoning test. DETAILED DESCRIPTION
[0027] In this embodiment, as shown in Figure 1 , a method for determining the scale ratio of an aircraft scale model used in an aircraft lightning zoning test, comprising:
[0028] Step 1: Obtain a three-dimensional aircraft model used in the aircraft lightning zoning test, and take the center of gravity of the three-dimensional aircraft model as the origin o, take the heading direction of the three-dimensional aircraft model as the y-axis, take the direction perpendicular to the y-axis as the z-axis, and take the direction from the belly to the back as the positive direction of the z-axis; both the y-axis and the z-axis are on the symmetry plane of the aircraft, and the x-axis is determined by the right-hand rule; thereby establishing an aircraft three-dimensional coordinate system o-xyz;
[0029] Step 2: Define that the three-dimensional aircraft model has max maximum points of aircraft surfaces, define the current maximum point as the nth point, and initialize n = 1, taking the highest point of the z-axis of the three-dimensional aircraft model in the aircraft three-dimensional coordinate system o-xyz as the nth point.
[0030] Step 3: Starting from the nth point, successively retain the surfaces with positive z-axis components of surface normals from top to bottom until the surface normal is perpendicular to the z-axis; obtain the nth continuous curve profile.
[0031] Step 4: Extend a surface in the downward direction of the z-axis of the nth continuous curve profile; if the extended nth surface intersects with other surfaces of the aircraft, stop extending, retain the extended nth surface, otherwise continue extending until the lowest point of the aircraft is reached, thereby obtaining the extended nth surface; in a specific implementation, if a surface is encountered when extending the surface downward, and the z-axis component of the surface normal is positive, then assign n + 1 to n, and repeat step 3 until all surfaces are extended to the bottom of the aircraft.
[0032] Step 5: Starting from the second highest point of the z-axis in the three-dimensional aircraft model in the three-dimensional coordinate system o-xyz, take the second highest point as the (n+1)th point, assign n+1 to n, and return to the process of steps 3-5 for processing until n = max, thereby obtaining max surfaces and forming a simplified surface.
[0033] Step 6: Define variable m and initialize m = 0; scale down the digital model according to the ratio i = 1 / (25 + m), where m is selected at equal intervals from 0 to 10; scale down the simplified surface according to the i-th ratio to obtain the scaled-down surface;
[0034] Step 7: Select a rectangular high-density rigid foam board that can accommodate an aircraft scaled down to ratio i as the processing substrate, and process the scaled-down digital model from Step 6; thus obtaining the i-th scaled-down simplified aircraft model.
[0035] Step 8: Lay aluminum foil or spray conductive paint on the surface of the processed scaled-down model, leaving the foam surface intact for the rest;
[0036] Step 9: After assigning m+1 to m, repeat steps 6 to 8 to produce simplified aircraft models with different scales i.
[0037] Step 10: Select any simplified aircraft model with a scale of i to conduct a lightning attachment point experiment and record the lightning attachment points:
[0038] Step 10.1: Place the simplified scaled-down aircraft model with a scale ratio of i directly below the rod electrode and directly above the grounding plate.
[0039] Step 10.2: The simplified aircraft scale model is fixed at one end of an insulator and the other end of the insulator is installed on a grounding plate. After the simplified aircraft scale model is installed, its attitude is that of an aircraft in level flight. The distance between any point on the simplified aircraft scale model and the discharge electrode (3) is greater than 50 / i meters, and the distance between the simplified aircraft scale model and the grounding plate is greater than the maximum size of the aircraft.
[0040] Step 10.3: Apply the positive polarity lightning voltage C-wave specified in the SAE5412 standard to the rod electrode. Although the negative polarity accounts for about 90%, positive polarity cloud-to-ground lightning often has a higher lightning current amplitude and destructiveness. Moreover, positive polarity long-gap discharge is more random and the attachment point is more difficult to predict. Therefore, a scaled-down test of the attachment point of positive polarity aircraft lightning is adopted. Record the position where the lightning arc enters the simplified scaled-down aircraft model. Conduct k tests continuously, where k is not less than 10.
[0041] Step 10.4: Conduct the tests sequentially from 1 / 35 to 1 / 25 scale models according to the above test method, and record the lightning attachment points.
[0042] Step 11, Judgment Method;
[0043] When the scaling ratio is i, the attachment results of the fuselage and vertical tail are extracted and the number of attachments is recorded as l. i机背 Next and l i垂尾 Then, when the scaling ratio is i, the attachment probabilities of the fuselage back and vertical tail are respectively P i机背 =l i机背 / n, P i垂尾 =l i机背 / n; if P i机背 =P i垂尾 When the scaling ratio is i, the test results are more consistent with the statistical data of real aircraft being struck by lightning, and the aircraft model is at its smallest at this time. This scaling ratio can be used as the scaling ratio for lightning zone test.
[0044] If P i机背 >P i垂尾 And when the scaling ratio is i / (1+i), P i / (1+i)机背 <P i / (1+i)垂尾 When the scaling ratio is (iB-(i / (1+i))A) / (BA), the test results are more consistent with the statistical data of real aircraft being struck by lightning, and the aircraft model is at its smallest at this time. This scaling ratio can be used as the scaling ratio for lightning zone test.
[0045] As the scale of the model increases, the probability of lightning strikes attaching to the vertical tail increases until it exceeds the probability of lightning strikes attaching to the fuselage back. This is because when the scale of the simplified aircraft model is small, the distance between the simplified aircraft model and the electrode also decreases, and the angle between the line connecting the vertical tail to the tip of the electrode and the perpendicular line of the electrode also increases, reducing the probability of lightning directly attaching to the vertical tail. Furthermore, the reduced distance between the simplified aircraft model and the electrode reduces the development time of the initial discharge on the vertical tail and shortens the upward discharge distance. Obviously, the probability of lightning strikes attaching to the fuselage back, located directly below the electrode, is higher than that of the vertical tail. As the scale of the simplified aircraft model increases, the probability of the vertical tail intercepting lightning increases, and the attachment probabilities of the vertical tail and the fuselage back become closer until the attachment probability of the vertical tail exceeds that of the fuselage back.
Claims
1. A method for determining the scale ratio of aircraft lightning zone tests, characterized in that: Follow these steps: Step 1: Obtain a 3D aircraft model for lightning zone testing. The origin o is the center of gravity of the 3D aircraft model. The y-axis is the heading direction of the 3D aircraft model, the z-axis is the direction perpendicular to the y-axis, and the positive z-axis direction is the direction from the belly to the back of the aircraft. Both the y-axis and z-axis lie on the plane of symmetry of the aircraft. The x-axis is determined using the right-hand rule. Thus, a 3D coordinate system o-xyz is established for the aircraft. Step 2: Define that the three-dimensional aircraft model has max maximum points on the aircraft surface, define the current maximum point as the nth point, and take the highest point of the z-axis of the three-dimensional aircraft model in the three-dimensional coordinate system o-xyz as the nth point, and initialize n=1; Step 3: Starting from the nth point, retain the surfaces of the 3D aircraft model whose z-axis component of the surface normal is positive from top to bottom until the surface normal is perpendicular to the z-axis; thus obtaining the nth continuous curve profile. Step 4: Extend a surface downward along the z-axis of the nth continuous curve profile; if the extended nth surface intersects with other surfaces of the aircraft, stop extending and retain the extended nth surface; otherwise, continue extending until the lowest point of the aircraft is reached, thus obtaining the extended nth surface. Step 5: Starting from the second highest point of the z-axis in the three-dimensional aircraft model in the three-dimensional coordinate system o-xyz, take the second highest point as the (n+1)th point, assign n+1 to n, and return to the process of steps 3-5 for processing until n=max, thereby obtaining max surfaces and forming a simplified surface. Step 6: Define variable m and initialize m=0; Select a scale i = 1 / (25 + m); scale down the simplified surface according to the i-th scale to obtain the scaled-down surface; Step 7: Use a rectangular high-density rigid foam board as the processing substrate and process it according to the scaled-down curved surface to obtain the i-th scaled-down simplified aircraft model. Step 8: Lay aluminum foil or spray conductive paint on the upper surface of the simplified aircraft model, leaving the foam surface intact on the remaining parts; Step 9: After assigning m+1 to m, repeat steps 6 to 8 to produce simplified aircraft models with different scales i. Step 10: Select any simplified aircraft model with a scale of i to conduct a lightning attachment point experiment and record the lightning attachment points: Step 10.1: Place the scaled-down simplified aircraft model of size i directly below the rod electrode and directly above the grounding plate; Step 10.2: Fix the simplified aircraft model with a scale of i to one end of the insulator, and install the other end of the insulator on the grounding plate; so that the attitude of the simplified aircraft model after installation is that of an aircraft in level flight, and the distance between any point on the simplified aircraft model and the rod electrode is greater than 50 / i meters, and the distance between the simplified aircraft model and the grounding plate is greater than the maximum length of the simplified aircraft model. Step 10.3: Apply a positive polarity lightning voltage C-wave to the rod electrode and record the position where the lightning arc enters the simplified aircraft model, i.e., the lightning attachment point; Step 10.4: Conduct k consecutive experiments as per Step 10.3, where k is not less than 10; Step 10.5: Conduct experiments on simplified aircraft models with different scales i according to the process of steps 10.1-10.4, and record the lightning attachment points; Step 11: In the simplified aircraft model test at scale i, extract the number of lightning attachment points belonging to the fuselage back and vertical tail from the lightning attachment points of k tests, and denot them as l. i机背 and l i垂尾 ; And the attachment probability P of the computer back and vertical tail. i机背 =l i机背 / k,P i垂尾 =l i机背 / k; Step 12: If P i机背 =P i垂尾 If i, it means that k tests with a scaling ratio of i meet the requirements, and the corresponding scaling ratio i is used as the scaling ratio of the lightning zoning test. If P i机背 >P i垂尾 And P i / (i+1)机背 <P i / (i+1)垂尾 Then (iB-(i / (1+i))A) / (BA) is taken as the lightning zone test reduction ratio, where A and B represent intermediate variables, and A= P i垂尾 -P i机背 B = P i / (i+1)垂尾 - P i / (i+1)机背 .
Citation Information
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