System and method for testing and measuring thermal injection ignition characteristics of ignition source of composite fuel tank fastener of airplane

Abstract

The invention discloses a system and a method for testing and measuring thermal jet ignition characteristics of an ignition source of a composite fuel tank fastener of an airplane. The testing system comprises an adjustable high-voltage direct-current charging power supply, a lightning current discharge unit for simulating a natural lightning environment, and a control, measurement and analysis unit for a thermal jet ignition test. According to the matching structure characteristics of the fastener carbon fiber composite material laminated plate, the correlation between the thermal spraying high-temperature airflow impact force and the thermal spark characteristics of the fastener carbon fiber composite material laminated plate interface and factors such as the matching structure of the fastener carbon fiber composite material laminated plate, climate environments such as temperature and humidity, lightning current electrical parameters and the like is obtained; a composite material fuel tank fastener ignition source thermal injection ignition characteristic database simulating the large aircraft flight environment is formed, and a foundation is laid for large aircraft composite material fuel tank ignition source lightning stroke multi-physical field modeling and ignition source mechanism and prediction algorithm research.

Description

Technical Field

[0001] The invention relates to a carbon fiber composite material testing technology, in particular to a testing method for fastener carbon fiber composite material properties, and in particular to a testing and measuring system and method for the thermal jet ignition properties of an ignition source of an aircraft composite fuel tank fastener. Background Art

[0002] Carbon fiber composite materials have the characteristics of low density, high strength, high modulus, high temperature resistance, chemical corrosion resistance, etc., and have the softness and processability of textile fibers. They are widely used in various fields such as aerospace, military and civilian industries. With the improvement of aircraft design and the advancement of carbon fiber composite material technology, the use of carbon fiber reinforced polymer composite materials CFRP (Carbon Fiber Reinforced Polymers) in large civil aircraft, military aircraft, drones and stealth aircraft is growing. At present, 50% of the main wing, tail, fuselage, floor and other structures of Boeing B787 are made of CFRP materials, the proportion of CFRP materials on Airbus A350XWA reaches 53%, the proportion of CFRP materials on China C919 is 12%, and the use of CFRP materials on the second-generation C929 will reach 50%, and composite fuel tanks will be used.

[0003] Lightning is a multiple continuous time-series discharge process that includes high-voltage shock waves, magnetic field forces and Joule heating effects caused by large currents. The strong current, strong magnetic field and accompanying strong shock waves generated by lightning cause the combustion, melting and explosion of the fuselage materials, which will cause the deformation of the fuselage structure and the reduction of strength, posing a serious threat to the safe operation of the aircraft. The fuel tank is an important component of the complex system of the aircraft, responsible for storing fuel, adjusting the center of gravity and cooling equipment. In the past 50 years, there have been 18 fuel tank explosion accidents in civil transport aircraft worldwide, resulting in 542 deaths. The fuel system composed of the entire fuselage or wing fuel tank is the most vulnerable system in the aircraft. The fuel tank explosion has become one of the main threats to civil aviation safety and has attracted serious attention from airworthiness management authorities around the world.

[0004] In order to fully reduce the probability of civil aircraft fuel tank explosion accidents, the Federal Aviation Administration of the United States, the European Aviation Safety Agency, and the Civil Aviation Administration of China have clearly specified the test methods and airworthiness requirements for aircraft fuel tank ignition sources. Aircraft fuel tank ignition sources include filament heating caused by heat under the current carrying capacity of the wire, static thermal injection, lightning attachment hot spots, friction heating, edge corona, and arcs / sparks, but the ignition mechanism can be summarized as "electrical ignition" and "thermal ignition".

[0005] In the new carbon fiber composite aircraft fuel tank structure, the assembly method and interface characteristics of the fasteners themselves are the main factors leading to electric field breakdown and current conduction hotspots. The sparks, temperature rise, and airflow jets caused at the structural interface become the source of fuel tank ignition.

[0006] The existing ignition source of large aircraft fuel tanks is mainly tested by the gas method using a spark source with a certain energy in a predetermined concentration of combustible gas. The energy of the spark discharge is obtained by calculating the energy of each component in the discharge circuit, such as the inductor and resistor. However, the judgment result is a digital quantity with only two results: "burning" and "non-burning", which makes it impossible to achieve quantitative prediction and safety assessment of the ignition source. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a test and measurement system and method for the thermal jet ignition characteristics of the ignition source of aircraft composite fuel tank fasteners, laying a foundation for the structural design and risk assessment of the ignition source of the lightning fuel tank.

[0008] The present invention is achieved through the following technical solutions:

[0009] A test and measurement system for thermal jet ignition characteristics of an ignition source of an aircraft composite fuel tank fastener, comprising a pulse thermal jet test power supply, a fastener carbon fiber composite laminate, a thermal jet injection clamping mechanism and an adjustment unit, a thermal jet ignition test control and measurement analysis unit, and a thermal jet spark monitoring unit;

[0010] The pulse thermal jet test power supply includes an adjustable high-voltage DC charging power supply and a lightning current generating unit simulating a natural lightning environment. The lightning current generating unit simulating a natural lightning environment generates a lightning current wave with an adjustable rise time. The charging voltage of the lightning current generating unit simulating a natural lightning environment is monitored online by a charging voltage monitoring sensor of the adjustable high-voltage DC charging power supply, and the charging voltage analog value is transmitted to the control and measurement analysis unit of the thermal jet ignition test;

[0011] The control and measurement and analysis unit of the thermal injection ignition test is used for the control of the test and the measurement and analysis of the thermal injection pulse parameters, and includes a control unit and a thermal injection measurement and analysis unit;

[0012] The thermal spray spark monitoring unit is used to obtain the occurrence and development process of the electric spark of the carbon fiber ignition source of the fastener, including a high-speed camera monitoring instrument and a high-speed camera control computer, and the camera process of the high-speed camera monitoring instrument is controlled by the high-speed camera control computer;

[0013] The hot spray injection clamping mechanism and the adjustment unit are used for clamping the sample fastener carbon fiber composite laminate and realizing arc and conduction injection application of lightning current to the sample fastener carbon fiber composite laminate;

[0014] Lightning current waves of different intensities are applied to the sample fastener carbon fiber composite laminate through a pulsed hot jet test power supply. The lightning current is applied to the fastener carbon fiber composite laminate in the form of arc and conduction injection through the hot jet injection clamping mechanism and the adjustment unit to form a hot jet spark. The hot jet spark monitoring unit is used to obtain the occurrence and development process of the electric spark of the fastener carbon fiber ignition source, and the correlation between the hot jet high-temperature airflow impact force and hot spark characteristics of the fastener carbon fiber composite laminate interface and the matching structure, temperature and humidity, and lightning current electrical parameters of the fastener carbon fiber composite laminate is obtained, so as to form a hot jet ignition feature database of the ignition source of the composite fuel tank fastener simulating the flight environment of large aircraft.

[0015] Furthermore, the adjustable high-voltage DC charging power supply is composed of an electronically controlled voltage regulator T1, a transformer T2, a rectifier silicon stack D and a current-limiting resistor Rc;

[0016] The lightning current generating unit simulating the natural lightning environment is composed of a main pulse energy storage capacitor C, a high-voltage discharge switch G, a waveform forming resistor R and a waveform forming inductor L. The fastener carbon fiber composite laminate and the hot spray injection clamping mechanism and the adjustment unit are connected in series in the circuit of the lightning current generating unit simulating the natural lightning environment.

[0017] Furthermore, the control unit includes a charging voltage monitoring circuit and a programmable controller. The charging voltage monitoring circuit of the control unit receives the signal transmitted by the charging voltage monitoring sensor, and outputs a control signal after processing by the programmable controller to control the discharge of the high-voltage discharge switch G of the lightning current generating unit simulating the natural lightning environment.

[0018] In addition, the programmable controller is also combined with the industrial control computer of the thermal injection measurement and analysis unit to control the connection / disconnection, high voltage increase / decrease and conduction of the high voltage discharge switch G in the charging process of the ignition characteristics test of the ignition source of the fastener carbon fiber composite laminate, so as to realize the automatic control of the ignition characteristics test process of the ignition source of the fastener carbon fiber composite laminate.

[0019] Furthermore, the thermal injection measurement and analysis unit includes a pulse current sensor, a digital oscilloscope and an industrial control computer. The pulse current sensor and the array oscilloscope jointly measure the lightning current between the high-voltage injection point and the low-voltage return point of the fastener carbon fiber composite laminate; the industrial control computer processes and analyzes the lightning current signal measured by the oscilloscope to obtain the thermal injection voltage U under the fastener assembly method and environmental temperature and humidity parameters.

[0020] Further, the thermal spray injection clamping mechanism and the adjustment unit include a thermal spray conduction injection clamping mechanism and a thermal spray arc injection clamping mechanism;

[0021] The thermal spray conduction injection clamping mechanism comprises a double-sided structural clamp with adjustable locking position installed on an insulating plate, the double-sided structural clamp is composed of two insulating baffles connected by bolts, and the mounting position between the two insulating baffles is adjusted by bolts to achieve the support of carbon fiber composite laminates with different fasteners; plate-shaped high-voltage injection electrodes and low-voltage return electrodes are respectively installed on the inner sides of the double-sided insulating baffles, the high-voltage end of the pulse power supply simulating the natural lightning environment is connected to the high-voltage injection electrode, and the low-voltage end is connected to the low-voltage return electrode of the electrode structure;

[0022] The hot spray arc injection clamping mechanism includes a clamp and adjustment mechanism and an electrode adjustment mechanism. The clamp and adjustment mechanism includes a bilateral structural clamp with an adjustable locking position installed on an insulating plate. The bilateral structural clamp consists of two insulating baffles connected by bolts. The mounting position between the two insulating baffles is adjusted by bolts to achieve the clamping of carbon fiber composite laminates with different fasteners; the electrode adjustment mechanism includes an electrode gap distance adjustment mechanism, a high-voltage injection electrode and two low-voltage return electrodes. The high-voltage injection electrode is installed directly above the fastener carbon fiber composite laminate through the electrode gap distance adjustment mechanism. The gap between the high-voltage injection electrode and the sample fastener carbon fiber composite laminate is adjusted by the electrode gap distance adjustment mechanism. The two low-voltage return electrodes are arranged on the inner side of the insulating baffles on both sides of the bilateral structural clamp; the two sides of the sample fastener carbon fiber composite laminate are respectively in close electrical contact with the low-voltage return electrode plate, and the mounting position of the baffle is adjusted by screws to achieve fixed clamping.

[0023] Furthermore, the electrode gap distance adjustment mechanism is a lifting mechanism arranged on one side of the clamp and the adjustment mechanism, and the high-voltage injection electrode is installed on the lifting mechanism. The height of the high-voltage injection electrode is adjusted by the lifting mechanism to adjust the gap between the high-voltage injection electrode and the carbon fiber composite laminate of the sample fastener.

[0024] A test and measurement method for the thermal jet ignition characteristics of an ignition source of an aircraft composite fuel tank fastener comprises the following steps:

[0025] 1). Selection and processing of test specimens: Select a number of carbon fiber composite laminates for fasteners for large aircraft and fuel tanks for temperature and humidity treatment to simulate the actual structure and flight environment of aircraft fuel tanks;

[0026] 2). Install the fastener carbon fiber composite laminate in the hot spray injection clamping mechanism and the adjustment unit, and connect the hot spray injection clamping mechanism and the adjustment unit high-voltage injection electrode and low-voltage return electrode to the lightning current generating unit circuit simulating the natural lightning environment;

[0027] 3). Apply lightning current pulses with different peak values ​​to the fastener carbon fiber composite laminate, and measure the lightning current data flowing through the fastener carbon fiber laminate by a pulse current sensor;

[0028] 4). The hot jet high temperature airflow impact force detection unit (4-21) and the analysis and processing unit of the hot jet spark monitoring unit are used to record the airflow impact force generated by the pyrolysis high temperature gas at the interface of the fastener carbon fiber composite material laminate caused by the lightning current arc and Joule heat effect; the high-speed camera monitoring instrument and high-speed camera control computer (41-2) of the hot jet spark monitoring unit are used to collect and store the hot spark phenomenon at the interface of the fastener carbon fiber composite material laminate;

[0029] 5). Using fastener carbon fiber composite laminates with different humidity and temperature, repeat step 2) to step 4), record the lightning current parameters flowing through the fastener carbon fiber composite laminate, the thermal injection pressure of the fastener carbon fiber composite laminate interface and the thermal ignition phenomenon;

[0030] 6). Change the assembly mode of the fastener carbon fiber composite laminate interface, that is, adjust the gap between the high-voltage injection electrode and the sample fastener carbon fiber composite laminate, repeat steps 1) to 5), and record the lightning current parameters flowing through the fastener carbon fiber composite laminate, as well as the airflow impact force and thermal spark phenomenon generated by the pyrolysis high-temperature gas at the fastener carbon fiber composite laminate interface;

[0031] 7) Process the thermal ignition state of the interface of the fastener carbon fiber composite laminate to form the correlation between the hot jet airflow pressure and ignition spark morphology of the hot jet characteristics of the fastener ignition source and the assembly method, temperature and humidity, and lightning current electrical parameters;

[0032] 8). Conduct statistical analysis on the test results of thermal jet ignition source, including the study of thermal jet airflow pressure, ignition spark characteristics and influencing factors of fastener carbon fiber composite laminates, establish a correlation database between the thermal jet ignition characteristics of fastener ignition sources and other factors, and use multi-factor regression method to obtain the evaluation method of the thermal jet ignition characteristics of fastener ignition sources.

[0033] The present invention has the following beneficial effects:

[0034] The invention relates to a test and measurement system and method for the thermal jet ignition characteristics of an ignition source of a composite fuel tank fastener of an aircraft. The test system comprises an adjustable high-voltage DC charging power supply, a lightning current discharge unit simulating a natural lightning environment, and a control, measurement and analysis unit for the thermal jet ignition test. Lightning current waves of different intensities are applied to the fastener carbon fiber composite laminate in the form of arc and conduction injection through a pulsed thermal jet test power supply to form thermal jet sparks, thereby obtaining the occurrence and development process of the electric spark of the fastener carbon fiber ignition source, and obtaining the correlation between the impact force of the thermal jet high-temperature airflow and the thermal spark characteristics of the interface of the fastener carbon fiber composite laminate and the matching structure, temperature and humidity, and lightning current electrical parameters of the fastener carbon fiber composite laminate.

[0035] The test and measurement analysis method of thermal jet ignition characteristics is based on the matching structural characteristics of the fastener carbon fiber composite laminate. Through the test data of the thermal jet ignition state characteristics of the fastener carbon fiber composite laminate under the action of lightning current, the data statistical method is used to finally obtain the correlation between the thermal jet high-temperature airflow impact force and thermal spark characteristics of the fastener carbon fiber composite laminate interface and the matching structure of the fastener carbon fiber composite laminate, climate environment such as temperature and humidity, lightning current electrical parameters and other factors, forming a database of thermal jet ignition characteristics of composite fuel tank fastener ignition sources simulating the flight environment of large aircraft, laying the foundation for the research of lightning multi-physics field modeling, ignition source mechanism and prediction algorithm of large aircraft composite fuel tank ignition source, and providing a basis for the structural design and risk assessment of lightning fuel tank ignition source. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a structural block diagram of the ignition source ignition characteristic test system for composite material fasteners of the present invention;.

[0037] Figure 2 This is a circuit principle block diagram of the ignition source ignition characteristic test system for composite material fasteners of the present invention;

[0038] FIG3 is a clamping structure for the ignition source ignition characteristic test of the composite material fastener of the present invention;

[0039] in, Figure 3a It is a schematic diagram of the structure of the thermal spray conduction injection clamping mechanism in the present invention;

[0040] Figure 3b It is a schematic diagram of the structure of the hot spray arc injection clamping mechanism in the present invention;

[0041] Figure 4 Flow chart of the test and analysis method for the ignition source ignition characteristics of fastener composite materials. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0043] See also Figure 1 As shown, the test and measurement system for the thermal jet ignition characteristics of the aircraft composite fuel tank fastener ignition source of the present invention is composed of a pulse thermal jet test power supply 1, a fastener carbon fiber composite laminate 2, a thermal jet injection clamping mechanism and an adjustment unit, a thermal jet ignition test control and measurement analysis unit 3 and a thermal jet spark monitoring unit 4.

[0044] The pulse thermal jet test power supply 1 is mainly composed of an adjustable high-voltage DC charging power supply 1-1 and a lightning current generating unit 1-2 simulating a natural lightning environment. During the actual test, the charging voltage of the lightning current generating unit 1-2 simulating a natural lightning environment is monitored online by the adjustable high-voltage DC charging power supply 1-1 through the charging voltage monitoring sensor 1-3, and the charging voltage analog quantity is transmitted to the control unit 31 of the control and measurement analysis unit 3 of the thermal jet ignition test. The function of the lightning current generating unit 1-2 simulating a natural lightning environment is to generate a lightning current wave with an adjustable rise time.

[0045] See also Figure 2 As shown, the principle circuit of the pulse thermal jet test power supply 1 for the electric spark characteristic test of the carbon fiber ignition source of the fastener of the present invention is shown, which mainly includes the circuit principle of two parts: an adjustable high-voltage DC charging power supply 1-1 and a lightning current generating unit 1-2 simulating a natural lightning environment.

[0046] The adjustable high-voltage DC charging power supply 1-1 is mainly composed of an electronically controlled voltage regulator T1, a transformer T2, a rectifier silicon stack D and a current limiting resistor Rc. The lightning current generating unit 1-2 simulating a natural lightning environment is mainly composed of a main pulse energy storage capacitor C, a high-voltage discharge switch G, a waveform forming resistor R and a waveform forming inductor L, which are electrically connected in series, and the sample fastener carbon fiber composite laminate 2 and its connection fixture hot injection injection clamping mechanism and adjustment unit are connected in series in the circuit of the lightning current generating unit 1-2 simulating a natural lightning environment.

[0047] See also Figure 1As shown, the function of the control and measurement and analysis unit 3 of the hot jet ignition test is to realize the control of the ignition characteristic test of the ignition source of the fastener carbon fiber composite laminate and the measurement and analysis of the hot jet pulse parameters, and is mainly composed of a control unit 31 and a hot jet measurement and analysis unit 32. Among them, the control unit 31 is mainly composed of a charging voltage monitoring circuit 31-1 and a programmable controller 31-2. The charging voltage monitoring circuit 31-1 of the control unit 31 receives the signal transmitted by the charging voltage monitoring sensor 1-3, and after being processed by the programmable controller 31-2, it can output a control signal to the programmable controller 31-2, thereby controlling the discharge of the high-voltage discharge switch G of the lightning current generating unit 1-2 simulating the natural lightning environment.

[0048] In addition, the programmable controller 31-2 is also combined with the industrial control computer 32-3 of the thermal injection measurement and analysis unit 32 to control the connection / disconnection, high voltage increase / decrease and conduction of the high voltage discharge switch G during the charging process of the fastener carbon fiber composite material laminate ignition source ignition characteristics test, thereby realizing automatic control of the fastener carbon fiber composite material laminate ignition source ignition characteristics test process.

[0049] The function of the thermal spray measurement and analysis unit 32 is to realize the control of the ignition characteristic test of the carbon fiber ignition source of the fastener and the measurement and analysis of the thermal spray pulse parameters, and to realize the process control of the ignition characteristic test of the ignition source of the fastener carbon fiber composite laminate and the measurement and analysis of the thermal spray pulse parameters. The thermal spray measurement and analysis unit 32 is mainly composed of a pulse current sensor 32-1, a digital oscilloscope 32-2 and an industrial control computer 32-3. The pulse current sensor 32-1 is combined with the array oscilloscope 32-2 to measure the lightning current between the high-voltage injection point and the low-voltage return point of the fastener carbon fiber composite laminate; the industrial control computer 32-3 processes and analyzes the lightning current signal measured by the oscilloscope, thereby obtaining the thermal spray voltage U under parameters including the fastener assembly method, ambient temperature and humidity, etc.

[0050] See also Figure 3a and Figure 3b As shown, the hot spray injection clamping mechanism and the adjustment unit are used to complete the clamping of the sample fastener carbon fiber composite laminate. The hot spray injection clamping mechanism and the adjustment unit include a hot spray conduction injection clamping mechanism and a hot spray arc injection clamping mechanism to realize the arc and conduction injection application of lightning current to the sample fastener carbon fiber composite laminate.

[0051] See also Figure 3aAs shown, the hot jet conduction injection clamping mechanism is a double-sided structural fixture A2 installed on an insulating plate A1 with an adjustable locking position. The double-sided structural fixture A2 is composed of two insulating baffles connected by bolts. The installation position of the baffles is adjusted by nuts A3 and screws A4 to achieve the support of different sample fastener carbon fiber composite laminates 2. A high-voltage injection electrode HV and a low-voltage return electrode LV are installed on the inner side of the double-sided insulating baffles. Their function is to connect the fastener carbon fiber composite laminate sample to the simulated natural lightning environment pulse power supply circuit 1-2, wherein the high-voltage end of the simulated natural lightning environment pulse power supply 1-2 is connected to the high-voltage injection electrode HV of the hot jet injection clamping mechanism, and the high-voltage injection electrode is a plate-shaped electrode with a certain thickness. The low-voltage end of the simulated natural lightning environment pulse power supply is connected to the low-voltage return electrode LV of the electrode structure.

[0052] See also Figure 3b As shown, the hot spray arc injection clamping mechanism consists of a clamp and adjustment mechanism and an electrode adjustment mechanism. The clamp and adjustment mechanism is a double-sided structural clamp A2 installed on an insulating plate A1 with an adjustable locking position. The double-sided structural clamp A2 consists of two insulating baffles connected by bolts. The installation position of the baffle is adjusted by a nut A3 and a screw A4 to achieve the support of the carbon fiber composite laminate 2 of different sample fasteners.

[0053] The electrode adjustment mechanism includes a group of metal electrodes and an electrode gap distance adjustment mechanism. The high-voltage injection electrode HV of the high-voltage arc of the hot spray test is fixedly installed just above the fastener of the sample fastener carbon fiber composite laminate, and has a certain and adjustable gap distance with the fastener carbon fiber composite laminate 2; two low-voltage return electrodes LV are arranged on the inner side of the insulating baffles on both sides of the bilateral structural fixture; the two sides of the sample fastener carbon fiber composite laminate are respectively in close electrical contact with the low-voltage return electrode plate, and the installation position of the baffle is adjusted by a screw to achieve fixed clamping.

[0054] The electrode gap distance adjustment mechanism is a lifting mechanism arranged on one side of the fixture and the adjustment mechanism, and the high-voltage injection electrode HV is installed on the lifting mechanism. The height of the high-voltage injection electrode is adjusted by the lifting mechanism, thereby adjusting the gap between the high-voltage injection electrode and the sample fastener carbon fiber composite laminate 2. The lifting mechanism can be a hydraulic lifting mechanism, a motor-driven screw lifting mechanism, or a pneumatic lifting mechanism driven by a cylinder.

[0055] like Figure 1As shown, the hot jet spark monitoring unit 4 observes the occurrence and development process of the electric spark of the carbon fiber ignition source of the fastener, and is mainly composed of a high-speed camera monitoring instrument 41-1, a high-speed camera control computer 41-2, a hot jet high-temperature airflow impact force detection unit 4-21 and an impact force analysis and processing unit 4-22. The main function of the high-speed camera monitoring instrument 41-1 is to observe the occurrence and development process of the electric spark of the carbon fiber ignition source of the fastener, and its camera process is controlled by the high-speed camera control computer 41-2. The electric spark process of the fastener carbon fiber ignition source is obtained through the hot jet spark monitoring unit 4, and the hot jet high-temperature airflow impact force detection unit 4-21 and the impact force analysis and processing unit 4-22 record the airflow impact force generated by the high-temperature gas pyrolyzed at the interface of the fastener carbon fiber composite material laminate caused by the lightning current arc and Joule heat effect. The thermal jet high-temperature airflow impact force detection unit 4-21 is composed of an impact sensor and a signal conditioning circuit. The impact sensor is installed at a certain distance from the side of the carbon fiber laminate fastener. It can be one or more. Its function is to detect the thermal impact force generated by the high-temperature gas ejection generated by the pyrolysis of the resin between the carbon fiber composite laminate interface, insulating materials, sealing materials and carbon fiber laminate plies of the sample fastener. The function of the impact force analysis and processing unit 4-22 is to conduct correlation between the thermal impact force and the assembly structure of the carbon fiber composite laminate of the sample fastener, the electrical parameters of the lightning impact force, etc.

[0056] See also Figure 4 , Fastener carbon fiber composite laminate ignition source ignition characteristics test and measurement method, the specific test and analysis process is as follows:

[0057] 1) Sample selection and processing: Select fastener carbon fiber composite laminate samples and process the samples, mainly including temperature and humidity (especially humidity), to simulate the actual flight environment of large aircraft. The sample temperature and humidity conditions have at least 5 points, denoted as S m1 To S m1 .

[0058] 2) The first fastener carbon fiber composite laminate specimens with different humidity are installed in a hot spray injection clamping mechanism, and the hot spray injection clamping mechanism and the adjustment unit are electrically connected to the hot spray simulated natural lightning environment lightning current generating unit circuit.

[0059] 3) Changing the peak value of the applied lightning current, obtaining the hot jet airflow impact force and ignition spark characteristics of the fastener carbon fiber composite laminate under different humidity conditions, using a pulse current sensor to detect the lightning current flowing through the fastener carbon fiber composite laminate 2, and using a hot jet spark monitoring unit 4 to detect the hot jet airflow impact force and hot spark characteristics of the fastener carbon fiber composite laminate 2.

[0060] 4) Changing the humidity of the fastener carbon fiber composite laminate, repeating process 2) to process 4), obtaining a database of the correlation between the lightning current flowing through the fastener carbon fiber composite laminate, the arc generated by the lightning current, the high-temperature hot jet airflow impact force generated by Joule heat at the interface of the fastener carbon fiber composite laminate, and the thermal spark characteristics and multiple factors such as sample temperature and humidity, and lightning current peak value.

[0061] 5) Similarly, the influencing factors of the impact force and thermal spark characteristics of the hot jet high-temperature airflow of the fastener may also include the assembly method of the fastener and the carbon fiber composite material, including clearance fit, interference fit, and filling of insulating materials with different dielectric constants between the fastener and the carbon fiber composite material, etc.

[0062] 6) Perform multi-factor regression statistical analysis on all lightning test results to obtain the correlation between the ignition source characteristics of typical fastener structures of fuel tanks and the lightning electrical parameters and temperature and humidity flight environment characteristics.

[0063] The test results of thermal spray and thermal spark characteristics are statistically analyzed, including the study of the impact force of thermal spray high-temperature airflow and thermal spark characteristics and influencing factors of the fastener carbon fiber composite laminate, which mainly includes two aspects: first, the temperature and humidity of the fastener carbon fiber composite laminate are adjusted to simulate different flight electrical environments of large aircraft, and lightning current waves of different intensities are applied, and the lightning current waves flowing through the fastener carbon fiber composite laminate are measured by a pulse current sensor, and the thermal spray high-temperature airflow impact force characteristics and thermal spray point spark characteristics of the fastener carbon fiber composite laminate interface are detected by the thermal spray spark monitoring unit 4; second, the thermal spray high-temperature airflow impact force characteristics and thermal spray point spark characteristics of the fastener carbon fiber composite laminate are analyzed, and a correlation database between the thermal spray high-temperature airflow impact force of the fastener carbon fiber composite laminate, the thermal spray point spark and temperature and humidity, lightning current parameters, interface assembly method and other multiple factors of the fastener carbon fiber composite laminate is established, and the multi-factor regression method is used to obtain the evaluation method of the high-temperature thermal spray airflow impact force and thermal spark characteristics of the fastener carbon fiber composite laminate interface.

Claims

1. A test and measurement system for the thermal jet ignition characteristics of an aircraft composite fuel tank fastener ignition source, characterized by: It comprises a pulse hot spray test power supply (1), a fastener carbon fiber composite material laminate (2), a hot spray injection clamping mechanism and an adjustment unit, a hot spray ignition test control and measurement analysis unit (3) and a hot spray spark monitoring unit (4); The pulse thermal spray test power supply (1) comprises an adjustable high-voltage direct current charging power supply (1-1) and a lightning current generating unit (1-2) for simulating a natural lightning environment. The lightning current generating unit (1-2) for simulating a natural lightning environment generates a lightning current wave with an adjustable rise time. The adjustable high-voltage direct current charging power supply (1-1) monitors the charging voltage of the lightning current generating unit (1-2) for simulating a natural lightning environment online through a charging voltage monitoring sensor (1-3), and transmits the charging voltage analog value to a control and measurement analysis unit (3) for a thermal spray ignition test. The control and measurement and analysis unit (3) of the thermal injection ignition test is used for controlling the test and measuring and analyzing the thermal injection pulse parameters, and comprises a control unit (31) and a thermal injection measurement and analysis unit (32); The thermal spray spark monitoring unit (4) is used to obtain the occurrence and development process of the electric spark of the carbon fiber ignition source of the fastener, and includes a high-speed camera monitoring instrument (41-1) and a high-speed camera control computer (41-2), and the camera process of the high-speed camera monitoring instrument (41-1) is controlled by the high-speed camera control computer (41-2); The hot spray injection clamping mechanism and the adjustment unit are used for clamping the sample fastener carbon fiber composite material laminate (2) and realizing arc and conduction injection application of lightning current to the sample fastener carbon fiber composite material laminate (2); Lightning current waves of different intensities are applied to the sample fastener carbon fiber composite laminate (2) by a pulse hot jet test power supply (1), and the lightning current is applied to the fastener carbon fiber composite laminate (2) in the form of arc and conduction injection through a hot jet injection clamping mechanism and an adjustment unit to form a hot jet spark. The hot jet spark monitoring unit (4) is used to obtain the occurrence and development process of the electric spark of the fastener carbon fiber ignition source, and obtain the relationship between the hot jet high-temperature airflow impact force and hot spark characteristics of the fastener carbon fiber composite laminate interface and the fastener carbon fiber composite laminate matching structure, temperature and humidity, and lightning current electrical parameters, so as to form a composite fuel tank fastener ignition source hot jet ignition feature database simulating the flight environment of a large aircraft.

2. The test and measurement system for the thermal jet ignition characteristics of the aircraft composite fuel tank fastener ignition source according to claim 1, characterized in that: The adjustable high-voltage direct current charging power supply (1-1) is composed of an electronically controlled voltage regulator T1, a transformer T2, a rectifier silicon stack D and a current limiting resistor Rc; The lightning current generating unit (1-2) for simulating a natural lightning environment is composed of a main pulse energy storage capacitor C, a high-voltage discharge switch G, a waveform forming resistor R and a waveform forming inductor L. The fastener carbon fiber composite material laminate (2) and the hot injection injection clamping mechanism and the adjustment unit are connected in series in the circuit of the lightning current generating unit (1-2) for simulating a natural lightning environment.

3. The test and measurement system for the thermal jet ignition characteristics of the aircraft composite fuel tank fastener ignition source according to claim 2, characterized in that: The control unit (31) comprises a charging voltage monitoring circuit (31-1) and a programmable controller (31-2). The charging voltage monitoring circuit (31-1) of the control unit (31) receives a signal transmitted from a charging voltage monitoring sensor (1-3), and outputs a control signal after being processed by the programmable controller (31-2) to perform discharge control on a high-voltage discharge switch G of a lightning current generating unit (1-2) simulating a natural lightning environment. In addition, the programmable controller (31-2) is also combined with the industrial control computer (32-3) of the thermal injection measurement and analysis unit (32) to control the connection / disconnection, high voltage increase / decrease and conduction of the high voltage discharge switch G during the charging process of the fastener carbon fiber composite material laminate ignition source ignition characteristic test, thereby realizing automatic control of the fastener carbon fiber composite material laminate ignition source ignition characteristic test process.

4. The test and measurement system for the thermal jet ignition characteristics of the aircraft composite fuel tank fastener ignition source according to claim 2, characterized in that: The thermal injection measurement and analysis unit (32) comprises a pulse current sensor (32-1), a digital oscilloscope (32-2) and an industrial control computer (32-3); the pulse current sensor (32-1) and the array oscilloscope (32-2) jointly measure the lightning current between the high-voltage injection point and the low-voltage return point of the fastener carbon fiber composite laminate; the industrial control computer (32-3) processes and analyzes the lightning current signal measured by the oscilloscope, thereby obtaining the thermal injection voltage U under the fastener assembly mode and environmental temperature and humidity parameters.

5. The test and measurement system for the thermal jet ignition characteristics of the aircraft composite fuel tank fastener ignition source according to claim 4 or 5, characterized in that: The thermal spray injection clamping mechanism and adjustment unit include a thermal spray conduction injection clamping mechanism and a thermal spray arc injection clamping mechanism; The thermal spray conduction injection clamping mechanism comprises a bilateral structural clamp (A2) with an adjustable locking position installed on an insulating plate (A1), the bilateral structural clamp (A2) being composed of two insulating baffles connected by bolts, and the mounting position between the two insulating baffles is adjusted by bolts to achieve the support of the carbon fiber composite laminate (2) with different fasteners; plate-shaped high-voltage injection electrodes (HV) and low-voltage return electrodes (LV) are respectively installed on the inner sides of the bilateral insulating baffles, the high-voltage end of the pulse power supply (1-2) simulating a natural lightning environment is connected to the high-voltage injection electrode (HV), and the low-voltage end is connected to the low-voltage return electrode (LV) of the electrode structure; The hot spray arc injection clamping mechanism comprises a clamp and adjustment mechanism and an electrode adjustment mechanism. The clamp and adjustment mechanism comprises a double-sided structural clamp (A2) with an adjustable locking position installed on an insulating plate (A1). The double-sided structural clamp (A2) consists of two insulating baffles connected by bolts. The mounting position between the two insulating baffles is adjusted by bolts to achieve the clamping of carbon fiber composite laminates (2) with different fasteners. The electrode adjustment mechanism comprises an electrode gap distance adjustment mechanism, a high-voltage injection electrode (HV) and two low-voltage return electrodes (LV). The high-voltage injection electrode (HV) is installed directly above the fastener carbon fiber composite laminate (2) through the electrode gap distance adjustment mechanism. The gap between the high-voltage injection electrode and the sample fastener carbon fiber composite laminate (2) is adjusted by the electrode gap distance adjustment mechanism. The two low-voltage return electrodes (LV) are arranged on the inner side of the insulating baffles on both sides of the double-sided structural clamp. The two sides of the sample fastener carbon fiber composite laminate are respectively in close electrical contact with the low-voltage return electrode plate, and the mounting position of the baffle is adjusted by screws to achieve fixed clamping.

6. The test and measurement system for the thermal jet ignition characteristics of the aircraft composite fuel tank fastener ignition source according to claim 5, characterized in that: The electrode gap distance adjustment mechanism is a lifting mechanism arranged on one side of the clamp and the adjustment mechanism, and the high-voltage injection electrode (HV) is installed on the lifting mechanism. The height of the high-voltage injection electrode is adjusted by the lifting mechanism to adjust the gap between the high-voltage injection electrode and the sample fastener carbon fiber composite material laminate (2).

7. A method for testing and measuring the thermal jet ignition characteristics of an aircraft composite fuel tank fastener ignition source based on the testing and measuring system of claim 6, characterized in that The steps include: 1). Selection and processing of test specimens: Select a number of carbon fiber composite laminates (2) for fasteners for large aircraft and fuel tanks for temperature and humidity treatment to simulate the actual structure and flight environment of aircraft fuel tanks; 2). Install the fastener carbon fiber composite laminate (2) in the hot spray injection clamping mechanism and the adjustment unit, and connect the hot spray injection clamping mechanism and the adjustment unit high voltage injection electrode (HV) and low voltage return electrode (LV) to the circuit of the lightning current generating unit (1-2) simulating the natural lightning environment; 3). Applying lightning current pulses with different peak values ​​to the fastener carbon fiber composite laminate (2), and measuring the lightning current data flowing through the fastener carbon fiber laminate by a pulse current sensor (32-1); 4). The hot jet high temperature airflow impact force detection unit (4-21) and the analysis and processing unit (4-22) of the hot jet spark monitoring unit (4) are used to record the airflow impact force generated by the high temperature gas pyrolyzed at the interface of the fastener carbon fiber composite laminate caused by the lightning current arc and Joule heat effect; A high-speed camera monitoring instrument (41-1) and a high-speed camera control computer (41-2) of a thermal spray spark monitoring unit (4) are used to collect and store thermal spark phenomena at the interface of a fastener carbon fiber composite material laminate; 5). Using fastener carbon fiber composite laminates with different humidity and temperature, repeat step 2) to step 4), record the lightning current parameters flowing through the fastener carbon fiber composite laminate, the thermal injection pressure of the fastener carbon fiber composite laminate interface and the thermal ignition phenomenon; 6). Change the assembly mode of the fastener carbon fiber composite laminate interface, that is, adjust the gap between the high-voltage injection electrode and the sample fastener carbon fiber composite laminate (2), repeat steps 1) to 5), and record the lightning current parameters flowing through the fastener carbon fiber composite laminate, as well as the airflow impact force and thermal spark phenomenon generated by the pyrolysis high-temperature gas at the fastener carbon fiber composite laminate interface; 7) Process the thermal ignition state of the interface of the fastener carbon fiber composite laminate to form the correlation between the hot jet airflow pressure and ignition spark morphology of the hot jet characteristics of the fastener ignition source and the assembly method, temperature and humidity, and lightning current electrical parameters; 8). Conduct statistical analysis on the test results of the thermal jet ignition source, including the study of the thermal jet airflow pressure, ignition spark characteristics and influencing factors of the fastener carbon fiber composite laminate (2), establish a correlation database between the thermal jet ignition characteristics of the fastener ignition source and other factors, and use a multi-factor regression method to obtain an evaluation method for the thermal jet ignition characteristics of the fastener ignition source.

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