Test System and Method for Repetitive Frequency Plasma Jet Ignition Characteristics of Propulsion System

Abstract

A test system and method for the ignition characteristics of a repetitive frequency plasma jet for a propulsion system. The system includes a repetitive frequency pulsed plasma jet generation system using an energetic doped working medium, a test chamber, and diagnostic equipment. The repetitive frequency pulsed plasma jet generation system using an energetic doped working medium includes six modules: a capillary jet device, a pulsed voltage generation circuit, a pulse current generation circuit, a thyristor trigger circuit, an LC series resonant charging circuit, and a control system. The diagnostic equipment includes a high-voltage probe, a Rogowski coil, a collimating mirror, an optical fiber, a spectrometer, a high-speed camera, a pressure sensor, a thermocouple, an oscilloscope, and a data acquisition card. The system controls the pressure in the test chamber through a controllable valve to simulate the working pressure of the engine in the propulsion system, realizes electrical and optical diagnosis of the parameters of any plasma jet in the repetitive frequency discharge sequence through the introduction of a counter, and measures the temperature and pressure in the test chamber during the ignition process of the propellant in the engine under the action of the repetitive frequency jet. The electrical parameters of the capillary discharge and the temperature and pressure parameters of the propellant combustion are synchronized in time through the trigger electrode voltage signal, aiming to achieve multi-dimensional characterization of the ignition efficiency under the action of the repetitive frequency capillary discharge plasma jet.

Description

Technical Field

[0001] The present invention relates to the field of plasma ignition tests for aerospace propulsion systems, and specifically to a test system and method for the ignition characteristics of a propulsion system under the action of repetitive plasma jets Background Art

[0002] An aerospace propulsion system refers to a propulsion system used by aircraft in the atmosphere and in space. There are various types of aerospace propulsion systems, including aeroengines, ramjets, rocket engines, electric propulsion systems, etc., which play important roles in different fields such as economy, military, and scientific research. Ignition of an aerospace propulsion system is the process of transitioning the system from a non-operating mode to an operating mode, and the reliability of propulsion system ignition is a prerequisite for its application. Currently, there are difficulties in reigniting the propulsion system under extreme conditions such as high altitude and high-speed oncoming flow, and new propellants with different molecular structures require higher ignition energies. The traditional spark ignition method has a low ignition success rate, and plasma ignition is one of the research hotspots. It uses discharge to form a locally high-temperature region and excites a large number of active particles to quickly ignite combustibles or enhance the combustion process. Common plasma ignition methods include plasma jet ignition, corona plasma ignition, transient plasma ignition, etc. It has advantages such as a large ignition area, short ignition delay time, and high ignition energy utilization rate. However, the above plasma ignition methods still have certain application limitations: the structure of a nanosecond pulse discharge plasma power supply is generally complex, the ion and neutral gas temperatures of non-equilibrium low-temperature plasma are relatively low, the heat flux is small, and the ignition ability for solid working media is limited; sliding arc discharge and plasma torch jet ignition require the introduction of gas flow, including complex structures such as gas path valves, which increases the complexity of the ignition system and may fail under some conditions

[0003] Capillary discharge ablates a low melting point and boiling point polymer material through an arc to form a plasma jet ejected from a capillary with an open end at one side. The plasma jet has characteristics such as high temperature (>10000K), high speed (1 - 10 km / s), high heat flux density (up to GW / m 2 level), and high outlet pressure (>MPa), and can be applied to fields such as space electric propulsion, material spraying, harmful substance treatment, and ignition of propellant. Capillary discharge is based on all-solid working media, does not rely on complex gas cylinders, gas paths, or pipeline systems, has a simple structure, and strong reliability. However, currently, capillary discharge ignition is mostly applied to the field of propellant ignition in a closed space, and there is no relevant research on its application to the ignition of aerospace propulsion systems. If we want to understand the ignition efficiency of capillary discharge plasma jets, relevant tests on plasma ignition characteristics need to be carried out

[0004] There are still the following deficiencies in the current research on repetitive capillary discharge plasma jet ignition

[0005] In the research on the characteristics of capillary discharge plasma jets, such as plasma temperature, plasma density, jet development morphology, etc., only single capillary discharge jets are studied, and there is no relevant research on the plasma characteristics of different plasma jets in a repetitive frequency capillary discharge sequence. There is a lack of characterization means for the ignition ability of repetitive frequency capillary discharge plasma jets. In addition, due to the strong dispersion in the time of capillary discharge, the delay time can reach the order of dozens to one hundred microseconds, making it difficult to accurately capture the discharge moment for setting the trigger delay in advance. However, repetitive frequency capillary discharge plasma jets can greatly improve the ignition efficiency under the condition of limited energy storage through the thermal accumulation effect.

[0006] In the application of capillary discharge plasma jet ignition, currently, capillary discharge plasma jet ignition is mainly applied to the field of propellant ignition. However, there is no relevant research on the application of repetitive frequency capillary discharge plasma jets to the ignition of aerospace propulsion systems, and it is necessary to clarify the interaction process between capillary discharge plasma jets and the propellants used in propulsion systems. Summary of the Invention

[0007] Aiming at the problems existing in the current experiments on the ignition characteristics of capillary discharge plasma jets, the purpose of the present invention is to provide a repetitive frequency plasma jet ignition characteristic test system and method for a propulsion system. For the ignition condition of repetitive frequency capillary discharge jets, the following two aspects of characteristic diagnosis can be achieved:

[0008] (1) Diagnose parameters such as plasma composition, plasma temperature, electron density, and jet development morphology of plasma jets in different orders in a repetitive frequency capillary discharge sequence, and obtain multi-dimensional characterization of the ignition ability of repetitive frequency plasma jets;

[0009] (2) Simulate the temperature and pressure changes in the test chamber of the propulsion system combustion chamber and the ignition and combustion processes of the propellant during the ignition process of repetitive frequency capillary discharge plasma jets.

[0010] To achieve the above purpose, the present invention adopts the following technical solutions:

[0011] A repetitive frequency plasma jet ignition characteristic test system for a propulsion system includes a repetitive frequency pulsed plasma jet generation system using an energetic doped working medium, a test chamber, and diagnostic equipment; among them, the repetitive frequency pulsed plasma jet generation system using an energetic doped working medium includes a capillary jet device 19, a pulsed voltage generation circuit 9, a pulsed current generation circuit 10, a thyristor trigger circuit 16, an LC series resonance charging circuit 17, and a control system 18; the diagnostic equipment includes a first high-voltage probe 28, a second high-voltage probe 29, a Rogowski coil 27, a collimating mirror 30, an optical fiber 31, a spectrometer 32, a high-speed camera 33, a pressure sensor 34, a thermocouple 43, an oscilloscope 45, and a data acquisition card 50;

[0012] In the capillary jet device 19 that can be repeatedly operated using an energy-enhanced working fluid, the energy-doped working fluid block 1 is made of active metal powder from the nanoscale to the micron scale, mixed with polymer powder, pressed, sintered, and machined mechanically into a modified energetic working fluid. A capillary channel 12 is machined at the axis, and a cylindrical channel 14 is machined on the side to communicate with the capillary channel 12. The energy-doped working fluid block 1 is coaxially installed inside the housing 8; the front of the housing 8 is connected to the front flange cover plate 5, and the rear is connected to the rear flange cover plate 7; the front flange cover plate 5 is machined with an expanding cathode nozzle 6 coaxially; the anode 2 is inserted into the capillary channel 12 from the rear of the energy-doped working fluid block 1, and the trigger electrode 3 is inserted into the cylindrical channel 14 on the side of the energy-doped working fluid block 1, dividing the capillary channel 12 between the end of the anode 2 and the front flange cover plate 5 into two parts between the anode 2 and the trigger electrode 3, called the trigger channel 15, and between the trigger electrode 3 and the front flange cover plate 5; insulators 4 are installed outside the anode 2 and the trigger electrode 3 to achieve electrical isolation from the housing, and the limit screw 11 is installed outside the insulator 4 and fixedly connected to the housing 8;

[0013] The connection relationship of each module in the repetitive pulse plasma jet generation system using the energy-doped working fluid is as follows: the high-voltage output terminal of the pulse voltage generation circuit 9 is connected to the trigger electrode 3 of the capillary jet device 19, and the low-level output terminal is connected to the front flange cover plate 5 of the capillary jet device 19; the high-voltage output terminal of the pulse current generation circuit 10 is connected to the anode 2 of the capillary jet device 19, and the low-voltage output terminal is connected to the front flange cover plate 5 of the capillary jet device 19. The front flange cover plate 5 of the capillary jet device 19 is grounded through a ground wire; the high-voltage output terminal of the LC series resonance charging circuit 17 is connected to the high-voltage end of the energy storage capacitor C1 in the pulse current generation circuit 10, and the low-voltage output terminal is connected to the low-voltage end of the energy storage capacitor C1 in the pulse current generation circuit 10 to achieve rapid charging of the energy storage capacitor C1; the two drive voltage output terminals of the thyristor trigger circuit 16 are respectively connected to the thyristor SCR2 in the pulse voltage generation circuit 9 to send a trigger signal 21, and to send a trigger signal 22 to the thyristor SCR1 in the pulse current generation circuit 10 to control the opening of the two thyristors; the control system 18 is connected to the LC series resonance charging circuit 17 and the thyristor trigger circuit 16 through optical fibers, and sends a charging start signal 23 to the LC series resonance charging circuit 17 and a trigger thyristor control opening signal 20 to the thyristor trigger circuit 16 according to the set frequency;

[0014] The front flange cover plate 5 of the capillary jet device 19 is connected to one end of the test cavity 44. The test cavity 44 is a coaxial cylindrical structure with a hollow interior. Propellant 37 is placed inside the test cavity 44 to simulate the ignition and combustion conditions of the propellant inside the propulsion system engine under plasma conditions. The other end of the test cavity 44 is connected to the pressure control valve 38. By presetting the internal pressure P0 of the cavity to be consistent with the actual engine conditions, when the propellant ignites during the test, if the internal pressure of the test cavity 44 is lower than the preset pressure P0, the pressure control valve 38 closes. When the internal pressure is higher than the preset pressure P0, it opens to release the pressure, and closes again when the internal pressure of the test cavity is lower than the preset pressure P0, so as to repeatedly control the internal pressure of the test cavity 44 to be consistent with the preset pressure P0. Two quartz observation windows 36 are opened on the side of the test cavity 44 to observe the internal plasma flow and combustion process; and a pressure measurement hole 35 is used to connect to the pressure sensor 34 to measure the internal pressure of the test cavity;

[0015] In terms of the connection of peripheral experimental equipment, the connection line between the anode 2 of the capillary jet device 19 and the high-voltage output terminal of the pulsed current generation circuit 10 passes through the Rogowski coil 27 to measure the discharge pulse current of the capillary discharge arc channel. The measured current signal 40 is divided into two paths. One path enters the first channel of the oscilloscope 45 and is collected, and the other path enters the counter 42. When the preset count is reached, the counter 42 sends a trigger signal 41 to the high-speed camera 33 and the spectrometer 32 to realize the acquisition of the development morphology and spectrum of a specific plasma jet in the repetitive discharge sequence;

[0016] The high-voltage end of the first high-voltage probe 28 is connected to the trigger electrode 3 of the capillary jet device 19, and the ground end is connected to the outer shell 8 to collect the voltage of the trigger electrode 3. The measured trigger electrode voltage signal 46 is divided into two paths. One path enters the second channel of the oscilloscope 45 and is collected, and the other path is used as a trigger signal to access the acquisition card 50;

[0017] The high-voltage end of the second high-voltage probe 29 is connected to the anode 2 of the capillary jet device 19, and the ground end is connected to the rear flange cover plate 7 to collect the voltage of the anode 2. The measured anode voltage signal 47 enters the third channel of the oscilloscope 45;

[0018] The high-speed camera 33 captures the development morphology of the plasma jet and the propellant ignition process inside the test chamber 44 through the quartz glass window 36. The axis direction of the high-speed camera 33 lens is perpendicular to the axis direction of the test chamber 44. The collimating mirror 30 collects the plasma jet and ignition combustion light inside the test chamber 44 through the quartz glass window 36, and enters the spectrometer 32 through the optical fiber 31 to analyze the spectrum of the plasma jet and ignition process. The pressure sensor 34 measures the internal pressure of the test chamber 44 during the discharge and ignition processes through the pressure measuring hole 35, and the pressure signal 48 is collected by the acquisition card 50. The thermocouple 43 is inserted into the test chamber 44 to measure the temperature of the propellant during the ignition process, and the temperature signal 49 is collected by the acquisition card 50.

[0019] For the study of plasma jet characteristics in an open space, the propellant 37 and the thermocouple 43 are not placed inside the test chamber 44, and the pressure control valve 38 is opened to connect the inside of the test chamber 44 with the external atmospheric environment. For the study of propellant ignition under the action of the plasma jet, the propellant 37 and the thermocouple 43 are placed inside the test chamber 44, and the pressure control valve 38 works normally to maintain the control of the internal pressure of the chamber.

[0020] In the pulse voltage generation circuit 9, the high-voltage end of the DC power supply U1 is connected to one end of the charging current-limiting resistor R C2 One end, and the other end of the charging current-limiting resistor R C2 Is divided into two paths. One path is connected to one end of the trigger capacitor C2 as the high-voltage end of the trigger capacitor C2, and the other path is connected to the anode of the thyristor SCR2. The other end of the trigger capacitor C2, that is, the low-voltage end, is divided into two paths. One path is connected to the low-voltage end of the DC power supply U1, and the other path is connected to one end of the primary coil of the pulse transformer T1. The cathode of the thyristor SCR2 is connected to the other end of the primary coil of the pulse transformer T1. The antiparallel diode VT2 is connected in parallel with the primary coil of the pulse transformer T1, its anode is connected to the low-voltage side of the trigger capacitor C2, and the cathode is connected to the cathode of the thyristor SCR2. The first trigger signal 21 of the thyristor trigger circuit 16 controls the gate turn-on of the thyristor SCR2 to control the discharge of the trigger capacitor C2 to the primary side of the pulse transformer T1. The high-voltage output end of the secondary side of the pulse transformer T1 is connected to one end of the DC-blocking capacitor C3. The other end of the DC-blocking capacitor C3 is led out and divided into two paths. One path is connected to one end of the saturable inductor L, and the other path is led out as the high-voltage output end of the pulse voltage of the pulse voltage generation circuit 9, which is connected to the trigger electrode 3 of the capillary discharge jet device 19. The other end of the wave-adjusting inductor L is connected to one end of the trigger loop current-limiting resistor R. The other end of the trigger loop current-limiting resistor R is divided into two paths. One path is connected to the low-voltage output end of the secondary side of the pulse transformer T1, and the other path is led out as the low-voltage output end of the pulse voltage of the pulse voltage generation circuit 9, which is connected to the front flange cover 5 of the capillary jet device 19.

[0021] In the pulsed current generating circuit 10, the high-voltage terminal and the low-voltage terminal of the energy storage capacitor C1 are respectively connected to the high-voltage output terminal and the low-voltage output terminal of the LC series resonance charging circuit 17. Before the start of a single discharge, the energy storage capacitor C1 is quickly charged to a preset voltage. The high-voltage terminal of the energy storage capacitor C1 is connected to the anode of the thyristor SCR1, and the thyristor SCR1 is anti-parallel connected with the diode VT1, where the anode of the thyristor SCR1 is connected to the cathode of the diode VT1, and the cathode of the thyristor SCR1 is connected to the anode of the diode VT1. The cathode terminal of the thyristor SCR1 is led out as the high-voltage output terminal of the pulsed current generating circuit 10 and is connected to the anode 2 of the capillary jet device 19. The second trigger signal 22 of the thyristor trigger circuit 16 is connected to the gate stage of the thyristor SCR1 to control the turn-on of the thyristor SCR1 and control the discharge of the energy storage capacitor C1. The connection wire of the low-voltage side of the energy storage capacitor C1 is led out as the low-voltage output terminal of the pulsed current generating circuit 10 and is connected to the front flange cover 5 of the capillary jet device 19.

[0022] In the LC series resonance charging circuit 17, for the primary part of the transformer T: The first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 in the N-channel IGBT module are connected in a bridge configuration, where each IGBT module S i is anti-parallel connected with the diode D i The collector of the IGBT module S i is connected to the cathode of the diode D i The emitter of the IGBT module S i is connected to the anode of the diode D i where i = 1, 2, 3, 4. The high-voltage terminal of the DC power supply U2 is connected to the collectors of the first IGBT module S1 and the third IGBT module S3. The emitter of the first IGBT module S1 is connected to the collector of the second IGBT module S2. The emitter of the third IGBT module S3 is connected to the collector of the fourth IGBT module S4. The emitters of the third IGBT module S3 and the fourth IGBT module S4 are connected together and commonly connected to the low-voltage side of the DC power supply U2. The gates of the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 are respectively connected to the all-hardware drive controller 24, and the all-hardware drive controller 24 respectively sends control signals to the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 to control their turn-on and turn-off. The emitter of the first IGBT module S1 is connected to one end of the resonant inductor L r One end of the resonant inductor L r The other end is connected to one end of the resonant capacitor C r One end of the resonant capacitor C rThe other end is connected to one end of the primary coil of transformer T, and the other end of the primary coil of transformer T is connected to the emitter of the third IGBT module S3; the secondary side of transformer T is connected to a diode full-bridge rectifier circuit composed of a first diode D5, a second diode D6, a third diode D7, and a fourth diode D8. The anode of the first diode D5 is connected to the cathode of the second diode D6, and the anode of the third diode D7 is connected to the cathode of the fourth diode D8. One end of the secondary side of transformer T is commonly connected to the anode of the first diode D5 and the cathode of the second diode D6, and the other end of the secondary side of transformer T is commonly connected to the anode of the third diode D7 and the cathode of the fourth diode D8. The cathode of the first diode D5 and the third diode D7 are connected and connected to one end of the filter inductor L2. The other end of the filter inductor L2 is connected to the collector of the fifth IGBT module S5. The emitter of the fifth IGBT module S5 is connected to the high-voltage output terminal of the LC series resonant charging circuit. The gate of the fifth IGBT module S5 is connected to the all-hardware drive controller 24. The all-hardware drive controller 24 controls the on and off of the fifth IGBT module S5 to control the on and off of the output circuit; the negative-polarity output terminal of the diode full-bridge rectifier circuit is connected to the low-voltage output terminal of the LC series resonant charging circuit module. A resistor divider 26 composed of a first resistor R1 and a second resistor R2 is connected in parallel between the high- and low-voltage output terminals of the LC series resonant charging circuit. One end of the first R1 is connected to the high-voltage output terminal, and the other end is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to the low-voltage output terminal and is connected to the anodes of the second diode D6 and the fourth diode D8; the voltage signal divided by the resistor divider 26 is input into the opto-isolation module 25 and is input into the all-hardware drive controller 24 after signal isolation; at the same time, the control signal 23 from the control system 18 controls the operation of the all-hardware drive controller 24, controls the start and stop of the PWM signals for driving the bridge arms of the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4, and the on and off of the fifth IGBT module S5.

[0023] A repetitive-pulse plasma jet generation system using an energetic-doped working medium, wherein the preparation method of the energetic-doped working medium block 1 in the capillary jet device 19 is as follows:

[0024] Mix nano- to micron-sized active metal powders with micron-sized polymer powders in a certain proportion. The active metal powders account for 3%-26% of the total powder mass, or dope some active metal oxide powders to improve the mechanical properties of the energetic material block, or add a small amount of ammonium perchlorate powder to increase the chemical energy released by the reaction. Place all the powders in a blender and shear-mix them evenly, then put them into a cylindrical hydraulic press mold with a hole in the middle. The filling is completed in one go, pressurize and hold, then slowly and gradually relieve the pressure of the hydraulic press to make a cylindrical blank with a through-hole in the middle. Let it stand to eliminate internal stress, and then sinter it in an argon-protected atmosphere. First, heat it at a heating rate of 50 degrees Celsius per hour to 370-390 degrees Celsius, hold for 2-6 hours, then cool it at a cooling rate of 50 degrees Celsius per minute to 327 degrees Celsius, hold for 2 hours, and then reduce the temperature to room temperature at a cooling rate of 50 degrees Celsius per minute. Finally, through machining, the axial position of the working fluid block is processed into a capillary channel 12, and a cylindrical channel 14 is vertically and inwardly processed on the side of the cylindrical working fluid block to communicate with the capillary channel 12.

[0025] The propellant is in the form of gas, liquid or solid.

[0026] The working method of the repetitive plasma jet ignition characteristic test system for the propulsion system described above includes two processes: the diagnosis of repetitive capillary discharge plasma jet parameters and the test of the ignition process of the propellant under the repetitive plasma jet. The specific working method is as follows:

[0027] (1) During the diagnosis of repetitive capillary discharge plasma jet parameters, open the pressure control valve 38 to connect the inside of the test chamber 44 with the outside atmosphere. Do not place the propellant 37 and the thermocouple 43 in the test chamber.

[0028] Start repetitive charge and discharge. The control system 18 controls the LC series resonant charging circuit 17 to charge the energy storage capacitor C1 in the pulse current generating circuit 10 with a constant current and charge the energy storage capacitor C1 to a preset voltage within dozens of milliseconds. When the trigger discharge time is reached, the control system 18 controls the thyristor trigger circuit 16 to trigger the thyristor SCR2 in the pulse voltage generating circuit 9 and the thyristor SCR1 in the pulse current generating circuit 10. The energy of the energy storage capacitor C1 in the pulse current generating circuit 10 is discharged through the arc channel in the capillary channel 12 of the jet device 19. The wire passing through the Rogowski coil 27 flows through a pulse current of thousands of amperes, and the output current signal 40 is measured by the Rogowski coil 27.

[0029] The current signal 40 is input into the counter 42, and the count of the counter is incremented by one. Each time a discharge is triggered, the count of the counter is incremented by one. When the set count number N is reached, the counter 42 sends a trigger signal to the high-speed camera 33 and the spectrometer 32. The high-speed camera 33 starts to collect the jet development morphology during the discharge process, and the spectrometer 32 collects the plasma jet spectrum;

[0030] When a capillary discharge ends and the set number of discharges is not reached, the control system 18 charges the energy storage capacitor C1 rapidly again, and so on; The oscilloscope 45 records the voltage and current waveforms of the entire discharge process;

[0031] (2) In the experiment on the ignition process of the propellant under the action of the repetitive plasma jet, the pressure control valve 38 is closed, the pressure threshold for its opening is set, the pressure inside the test chamber 44 during the propellant combustion process is controlled, the propellant 37 is fixed inside the test chamber 44, and the thermocouple 43 measures the temperature in the test chamber 44;

[0032] Start the repetitive charge and discharge. The oscilloscope 45 collects the voltage and current waveforms during the discharge process. The high-speed camera 33 takes pictures of the process of the plasma jet acting on the propellant 37 and the ignition and combustion process. The spectrometer 32 collects the spectra of the above processes. The pressure sensor 34 collects the pressure in the test chamber 44 during the propellant ignition process, and the thermocouple 43 collects the temperature change data in the test chamber 44 during the ignition process.

[0033] The data processing method after the experiment is as follows:

[0034] In the measurement and processing of electrical parameters, the discharge delay t d is calculated in the following way: For each capillary discharge in the repetitive sequence, the moment t1 when the current i starts to rise collected from the Rogowski coil 27 is subtracted by the moment t0 when the voltage u trig peak value corresponds to the breakdown of the trigger gap;

[0035] t d = t1 - t0 (1)

[0036] The arc channel resistance R arc is calculated according to the following formula:

[0037]

[0038] where u anode represents the anode voltage measured by the second high-voltage probe 29, and i represents the current measured by the Rogowski coil 27;

[0039] The arc power deposition P arc is calculated according to the following formula:

[0040] P arc = |uanode i| (3)

[0041] Arc channel energy deposition E arc It is calculated according to the following formula:

[0042]

[0043] where t1 is the moment when the current i starts to rise collected by the Rogowski coil 27, and t2 is the moment when the current i drops to 0 collected by the Rogowski coil 27.

[0044] In the measurement and processing of optical parameters, the morphology and evolution process of the plasma jet are photographed by the high-speed camera 33; the components of the plasma jet are compared by the emission spectral characteristic line wavelengths collected by the spectrometer 32 with the line wavelengths in the atomic spectral emission database. When the line wavelength position collected by the spectrometer is consistent with the line position of a certain element component in the database, it is considered that the element component exists in the plasma jet;

[0045] The electron temperature of the plasma jet is calculated by the Boltzmann slope method: as shown in formula (5):

[0046]

[0047] In the formula: I g ——Spectral line emission intensity; λ——Wavelength / nm; g——Statistical weight of the upper energy level; A——Spontaneous emission coefficient / s-1; E exc ——Wave number of the excitation energy of the high energy state / cm -1 ; h——Planck constant; c——Speed of light in vacuum / m·s -1 ; n m ——Atomic density; z——Temperature-dependent partition function.

[0048] Select several spectral lines of a certain type of particle, and find the corresponding spectral line emission intensity I in the measured spectrum g ; According to the known g, A, E exc and the measured I g , make a scatter plot of E exc -lg(I g λ) / (gA) and fit a straight line; calculate the jet electron temperature T e =-0.625 / k from the slope k of the straight line; at the same time, since only the slope needs to be calculated, the spectral line emission intensity is calculated using the relative intensity.

[0049] In the experiment of the ignition process of the propellant under the action of a repetitive pulsed plasma jet, it is necessary to measure the temperature of the propellant and the pressure in the test chamber during the ignition process of the propellant; both the oscilloscope 45 and the acquisition card 50 are triggered once by the rising edge of the voltage signal of the first high-voltage probe 28 to achieve the time synchronization of the temperature signal 49, the pressure signal 48, the current signal 40, the trigger electrode voltage signal 46, and the anode voltage signal 47; the temperature signal 49 and the pressure signal 48 are used to represent the ignition moment and the plasma ignition efficiency; since a large amount of high-temperature and high-pressure gas is released during the ignition of the propellant, the internal pressure of the test chamber 44 will increase significantly. The ignition delay is defined as the time delay t from the moment t0 when the oscilloscope 45 and the acquisition card 50 are triggered by the first voltage pulse signal of the trigger electrode 3 collected by the first high-voltage probe 28 to the moment when the pressure sensor 34 in the test chamber 44 collects the pressure signal 48 and starts to rise to 10% of the maximum pressure. fd ;

[0050] t fd = t 10％ - t0 (6)

[0051] The improvement effect of the plasma jet on the ignition efficiency of the propellant is characterized by the pressure rise rate. The pressure rise rate r p is defined as the pressure change ΔP = P 90％ - P 10％ when the pressure rises from 10% to 90% of the maximum value during ignition, divided by the time Δt = t 90％ - t 10％ ;

[0052]

[0053] The pulsed plasma jet generation system using an energetic doped working medium can repeatedly generate plasma jets at a set frequency. Its working process is as follows:

[0054] In each cycle, the control system 18 controls the DC power supply U2 in the LC series resonant charging circuit 17 to start charging by sending a charging start signal 23 to the all-hardware drive controller 24 in the LC series resonant charging circuit; the control system 18 inputs a turn-on signal 20 to the thyristor trigger circuit 16 at a set frequency to trigger a single capillary discharge to generate a plasma jet; each cycle of generating a plasma jet is divided into two steps: energy storage system charging and pulsed discharge to generate a plasma jet.

[0055] 1) Charging process of the energy storage system: The control system 18 sends a charging start signal 23 to the all-hardware drive controller 24 in the LC series resonant charging circuit 17, and the LC series resonant charging circuit 17 starts to work; the all-hardware drive controller 24 inputs complementary PWM drive signals with a duty cycle of 25% to the first IGBT module S1 and the third IGBT module S3 as a group, and the second IGBT module S2 and the fourth IGBT module S4 as a group, to control the bridge arms to turn on alternately; convert the direct current provided by the DC power supply U2 into alternating current, step up the voltage through the transformer T, and convert it into direct current again through the diode full-bridge rectifier circuit, so as to charge the energy storage capacitor C1 to a high voltage of up to 2000V; the resistor voltage divider 26 connected to the output terminal collects the voltage of the energy storage capacitor C1, divides the voltage of the energy storage capacitor C1 of 0-2000V into a voltage signal of 0-1.5V, inputs it into the all-hardware drive controller 24 through the optoelectronic isolation module 25, compares it with the set charging voltage through the operational amplifier circuit, and judges whether the voltage of the energy storage capacitor C1 reaches the preset voltage through the gate circuit group. When the voltage of the energy storage capacitor C1 reaches the set charging voltage, the all-hardware drive controller stops inputting drive PWM signals to the first IGBT module S1, the second IGBT module S2, the third IGBT module S3 and the fourth IGBT module S4, and controls the fifth IGBT module S5 to turn off the charging circuit;

[0056] 2) Process of generating plasma jet by pulsed discharge: When reaching the trigger discharge moment, the control system 18 transmits a trigger plasma jet signal to the thyristor trigger circuit 16; the thyristor trigger circuit 16 transmits a second trigger signal 22 to the thyristor SCR1 in the pulsed current generation circuit 10 to control its conduction, and applies the voltage of the energy storage capacitor C1 between the anode 2 and the front flange cover 5. During the discharge process, the front flange cover 5 serves as the cathode; after a delay, the thyristor trigger circuit 16 inputs a first trigger signal 21 to the thyristor SCR2 in the pulsed voltage generation circuit to control its conduction, applies a trigger high-voltage pulse to the trigger electrode 3, and induces a surface discharge in the trigger channel 15 between the end of the anode 2 and the end of the trigger electrode 3;

[0057] The surface discharge of the trigger channel 15 forms an arc, and the high-conductivity plasma formed by ablation of the capillary tube wall material of the trigger channel 15 moves towards the front flange cover plate 5 acting as the cathode. When the plasma reaches the cathode front flange cover plate 5, the capillary channel between the anode 2 and the cathode front flange cover plate 5 is filled with high-conductivity plasma. The channel between the anode 2 and the cathode front flange cover plate 5, that is, the high-voltage output terminal and the low-voltage output terminal of the pulsed current generation circuit 10 are short-circuited. A discharge loop is formed from the high-voltage output terminal of the pulsed current generation circuit 10 - the anode 2 - the arc in the capillary channel 12 - the cathode front flange cover plate 5 - the low-voltage output terminal of the pulsed current generation circuit 10. The electrical energy stored in the energy storage capacitor in the pulsed current generation circuit 10 starts to be released through the arc load in the capillary channel 12. The high-temperature arc radiation energy ablates the energy-doped working medium material in the capillary tube wall of the solid working medium to form a high-temperature and high-pressure plasma. The active metal powder and the polymer powder components in the plasma undergo a chemical reaction to release energy, further increasing the internal energy of the plasma jet. The inner wall material of the capillary channel 12 of the energy-doped working medium block 1 continuously undergoes phase change and decomposition and enters the interior of the capillary channel 12, increasing the internal pressure of the cavity, causing the plasma to continuously move towards the cathode nozzle 6 under the action of the pressure gradient, and finally ejecting outward to generate a high-temperature and high-density plasma jet 13;

[0058] The repetitive pulsed plasma jet generation system using the energy-doped working medium triggers and conducts the capillary channel 12 between the anode 2 and the front flange cover plate 5 through plasma jet. The ablation mass of the working medium block and the electrode during a single discharge is in the range of several milligrams to dozens of milligrams, and there is no obvious change in its morphology after a single discharge. Immediately after the energy storage of the pulsed current generation circuit 10 is completed, the next discharge starts.

[0059] The present invention proposes a system for applying a repetitive pulsed capillary discharge plasma jet to the ignition test of a propulsion system, which has significant differences from the application of capillary discharge to the ignition of propellant in terms of combustion chamber volume, ignition pressure, the number of jets required for ignition, and the properties of propellant and propellant:

[0060] (1) Capillary discharge for propellant ignition is carried out in the electrothermal chemical cannon body with limited space. The space is limited, and the ignition characteristic test is mainly carried out in a closed bomb. The ignition transient pressure can reach above the order of 100 MPa, and generally a single capillary discharge can ignite the propellant; for the ignition of the propulsion system, it is generally applied to a combustion chamber with a larger volume. The working pressure of the propulsion system combustion chamber is generally from a few atmospheres to about 15 MPa, significantly lower than the ignition pressure of the electrothermal chemical cannon. Moreover, when applied to the ignition of the propulsion system, when the volume and weight of the energy storage system are limited, the capillary jet device needs to operate in a repetitive pulsed mode, and sometimes multiple jet actions are required to ignite the propellant;

[0061] (2) There are also differences between propellant and propellent in terms of chemical composition and combustion characteristics. Generally, the combustion rate of propellant is much higher than that of propellent, and there must be differences in their ignition characteristics.

[0062] Compared with the prior art, the present invention has the following advantages:

[0063] 1. An experimental system for the ignition characteristics of repetitive pulsed plasma jets for a propulsion system proposed by the present invention realizes the electrical and optical diagnosis of any plasma jet in the repetitive pulsed plasma jet sequence by introducing a counter, and obtains multi-dimensional characterization of the ignition ability of the plasma jet; as well as the analysis of the combustion chamber temperature, pressure, jet morphology and spectrum during the ignition process of the propellent under the action of the repetitive jet, and realizes the time synchronization of each signal acquisition through the pulsed voltage signal of the trigger electrode. It can realize multi-dimensional characterization of the ignition process of repetitive pulsed plasma jets.

[0064] 2. An experimental system for the ignition characteristics of repetitive pulsed plasma jets for a propulsion system proposed by the present invention is oriented to the specific combustion chamber volume, pressure environment and combustion properties of the propellent in the propulsion system, and controls the internal pressure of the test chamber to be consistent with the pressure in the engine through a controllable valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Fig. is an experimental system for the ignition characteristics of repetitive pulsed plasma jets for a solid propellant described in the present invention.

[0066] Figure 2a And Figure 2b are respectively schematic diagrams of the connection between the sensing device and the acquisition device (please explain the two figures separately).

[0067] Figure 3 is a schematic diagram of the positions of the capillary channel and the side cylindrical through hole of the energetic material block.

[0068] Figure 4 is a schematic diagram of the pulsed voltage generation circuit.

[0069] Figure 5 is a schematic diagram of the pulsed current generation circuit.

[0070] Figure 6 is a schematic diagram of the series resonant charging circuit.

[0071] Figure 7 is a schematic diagram of the waveform of the voltage and current of a single capillary discharge changing with time and the definition of the trigger, discharge start and end times.

[0072] Figure 8 is a waveform diagram of the arc channel resistance calculated by a single capillary discharge changing with time.

[0073] Figure 9Waveform diagrams of the energy deposition and power deposition in the arc channel over time for single-shot capillary discharge calculation.

[0074] Figure 10 High-speed photography of the expansion of the capillary discharge plasma jet in an atmospheric pressure environment.

[0075] Figure 11 Emission spectrum of the capillary discharge plasma jet and Cu I spectral line.

[0076] Figure 12 Flow chart of the ignition system for achieving repetitive capillary discharge.

[0077] Figure 13 Schematic diagram of the voltage pulse and pressure waveform curves of the first trigger electrode in the ignition of the propellant under the action of the repetitive plasma jet.

[0078] Figure 14 Diagram of the corresponding relationship between the input of the counter repetitive current signal and the output of the trigger signal.

[0079] Figure 15 Waveform diagrams of the charging and discharging current and voltage at a repetition frequency of 20 Hz using an aluminum-based energetic working fluid.

[0080] Figure 16 Sintering temperature curve of the energy-enhanced working fluid.

[0081] Figure 17 Flow chart for preparing the energy-enhanced capillary discharge working fluid block.

[0082] Figure 18 Voltage waveform diagram of the LC series resonant charging power supply charging the energy storage capacitor C1. Specific embodiments

[0083] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0084] As Figure 1 shown in FIGS. 1 and 2, a repetitive plasma jet ignition characteristic test system for a propulsion system includes a repetitive pulse plasma jet generation system using an energetic doped working fluid, a test chamber 44, and diagnostic equipment. The repetitive pulse plasma jet generation system using an energetic doped working fluid includes six modules: a capillary jet device 19, a pulse voltage generation circuit 9, a pulse current generation circuit 10, a thyristor trigger circuit 16, an LC series resonant charging circuit 17, and a control system 18. The diagnostic equipment includes a first high-voltage probe 28, a second high-voltage probe 29, a Rogowski coil 27, a collimating mirror 30, an optical fiber 31, a spectrometer 32, a high-speed camera 33, a pressure sensor 34, a thermocouple 43, an oscilloscope 45, and an acquisition card 50.

[0085] As Figure 1As shown, in the reusable capillary jet device 19 using an energy-enhanced modified working fluid, as Figure 3 shown, the energy-doped working fluid block 1 is made of micron- to nanoscale aluminum powder or boron powder, mixed with polymer powders such as polytetrafluoroethylene, high-density polyethylene, and polyether ether ketone, pressed, sintered, and machined into a modified energy-containing working fluid. A capillary channel 12 is machined at the axis, and a cylindrical channel 14 is machined on the side to communicate with the capillary channel 12. The energy-doped working fluid block 1 is coaxially installed inside the outer shell 8; the front of the outer shell 8 is connected to the front flange cover plate 5, and the rear is connected to the rear flange cover plate 7; the front flange cover plate 5 is coaxially machined with an expanding cathode nozzle 6; the anode 2 is inserted into the capillary channel 12 from the rear of the energy-doped working fluid block 1, and the trigger electrode 3 is inserted into the cylindrical channel 14 on the side of the energy-doped working fluid block 1, dividing the capillary channel 12 between the end of the anode 2 and the front flange cover plate 5 into two parts: the part between the anode 2 and the trigger electrode, called the trigger channel 15, and the part between the trigger electrode 3 and the front flange cover plate 5; insulators 4 are installed outside the anode 2 and the trigger electrode 3 to achieve electrical isolation from the outer shell, and the limit screw 11 is installed outside the insulator 4 and fixedly connected to the outer shell 8.

[0086] As Figure 1 shown, the connection relationship of each module in the repetitive pulse plasma jet generation system using the energy-doped working fluid is as follows: the high-voltage output terminal of the pulse voltage generation circuit 9 is connected to the trigger electrode 3 of the capillary jet device 19, and the low-level output terminal is connected to the front flange cover plate 5 of the capillary jet device 19; the high-voltage output terminal of the pulse current generation circuit 10 is connected to the anode 2 of the capillary jet device 19, and the low-voltage output terminal is connected to the front flange cover plate 5 of the capillary jet device 19. The front flange cover plate 5 of the capillary jet device 19 is grounded through a ground wire; the high-voltage output terminal of the LC series resonance charging circuit 17 is connected to the high-voltage terminal of the energy storage capacitor C1 in the pulse current generation circuit 10, and the low-voltage output terminal is connected to the low-voltage terminal of the energy storage capacitor C1 in the pulse current generation circuit 10 to achieve rapid charging of the energy storage capacitor C1; the two drive voltage output terminals of the thyristor trigger circuit 16 are respectively connected to the thyristor SCR2 in the pulse voltage generation circuit 9 to send the trigger signal 21, and to the thyristor SCR1 in the pulse current generation circuit 10 to send the trigger signal 22 to control the conduction of the two thyristors; the control system 18 is connected to the LC series resonance charging circuit 17 and the thyristor trigger circuit 16 through optical fibers, and sends the charging start signal 23 to the LC series resonance charging circuit 17 and the trigger thyristor control conduction signal 20 to the thyristor trigger circuit 16 according to the set frequency.

[0087] As Figure 1As shown in the figure, the front flange cover plate 5 of the capillary jet device 19 is connected to one end of the test cavity 44. The propellant 37 is placed inside the test cavity 44 to simulate the ignition and combustion conditions of the propellant inside the engine of the propulsion system under plasma conditions. The other end of the test cavity 44 is connected to the pressure control valve 38. By presetting the internal pressure P0 of the cavity to be consistent with the actual engine conditions, the test cavity 44 is made of high-temperature-resistant metal, and the overall structure is a hollow cylindrical structure with an inner diameter of not less than 25 mm and a wall thickness of not less than 20 mm to ensure sufficient strength to simulate the high-temperature and high-pressure environment during engine operation. When the propellant ignites during the test, if the internal pressure of the test cavity 44 is lower than the preset pressure P0, the pressure control valve 38 closes, and when the internal pressure is higher than the preset pressure P0, the pressure is released. When the internal pressure of the test cavity is lower than the preset pressure P0, it closes again, and so on to control the internal pressure of the test cavity 44 to be consistent with the preset pressure P0. Two quartz observation windows 36 are opened on the side of the test cavity 44 to observe the internal plasma flow and combustion process; and a pressure measurement hole 35 with a diameter of 1 mm is used to connect the pressure sensor 34 to measure the internal pressure of the test cavity.

[0088] As Figure 1 shown, in terms of the connection of the peripheral experimental equipment, the connection wire between the anode 2 of the capillary jet device 19 and the high-voltage output end of the pulse current generation circuit 10 passes through the Rogowski coil 27 to measure the discharge pulse current of the capillary discharge arc channel. The measured current signal 40 is divided into two paths. One path enters the first channel of the oscilloscope 45 to be collected, and the other path enters the counter 42. When the preset count is reached, the counter 42 sends a trigger signal 41 to the high-speed camera 33 and the spectrometer 32 to collect the development morphology and spectrum of a specific plasma jet in the repetitive discharge sequence.

[0089] As Figure 1 shown in Fig. 2, the high-voltage end of the first high-voltage probe 28 is connected to the trigger electrode 3 of the capillary jet device 19, and the grounded end is connected to the housing 8 to collect the voltage of the trigger electrode 3. The measured trigger electrode voltage signal 46 is divided into two paths. One path enters the second channel of the oscilloscope 45 to be collected, and the other path is used as a trigger signal to access the acquisition card 50. The acquisition card 50 is set to the rising-edge single-shot trigger mode, that is, it starts to collect signals after receiving the first rising-edge level signal.

[0090] The high-voltage end of the second high-voltage probe 29 is connected to the anode 2 of the capillary jet device 19, and the grounded end is connected to the rear flange cover plate 7 to collect the voltage of the anode 2. The measured voltage signal 47 enters the third channel of the oscilloscope 45.

[0091] As Figure 1As shown, the high-speed camera 33 captures the development morphology of the plasma jet and the ignition and combustion process of the propellant inside the test chamber 44 through the quartz glass window 36; the collimating mirror 30 collects the plasma jet and the ignition and combustion light inside the test chamber 44 through the quartz glass window 36, and enters the spectrometer 32 through the optical fiber 31 to analyze the spectrum of the plasma jet and the ignition process.

[0092] As Figure 1 shown in Fig. 2, the pressure sensor 34 measures the internal pressure of the test chamber 44 during the ignition process through the pressure measuring hole 35, and the pressure signal 48 is collected by the acquisition card 50. The thermocouple 43 is inserted into the propellant 37 to measure the temperature of the propellant during the ignition process, and the temperature signal 49 is collected by the acquisition card 50.

[0093] In the study of the characteristics of plasma jets in an open space, the propellant 37 and the thermocouple 43 are not placed inside the test chamber 44, and the pressure control valve 38 is opened to connect the inside of the test chamber 44 with the external atmospheric environment; in the study of plasma jet ignition, the propellant 37 and the thermocouple 43 are placed inside the test chamber 44, and the pressure control valve 38 operates normally to maintain control of the internal pressure of the chamber.

[0094] As Figure 4 shown, in the pulse voltage generation circuit 9, the voltage of the DC power supply U1 is 800V, the charging current limiting resistor R C2 has a resistance value of 10Ω, and the capacitance of the trigger capacitor C2 is 2.5 μF. The high-voltage terminal of the DC power supply U1 is connected to one end of the charging current limiting resistor R C2 R C2The other end is divided into two paths. One path is connected to one end of the trigger capacitor C2 to serve as the high-voltage end of the trigger capacitor C2, and the other path is connected to the anode of the thyristor SCR2. The connection line of the other end (low-voltage end) of the trigger capacitor C2 is divided into two paths. One path is connected to the low-voltage end of the DC power supply U1, and the other path is connected to one end of the primary coil of the pulse transformer T1. The cathode of the thyristor SCR2 is connected to the other end of the primary coil of the pulse transformer T1. The antiparallel diode VT2 is connected in parallel with the primary coil of the pulse transformer T1, its anode is connected to the low-voltage side of the trigger capacitor C2, and its cathode is connected to the cathode of the thyristor SCR2. The first trigger signal 21 of the thyristor trigger circuit 16 controls the gate of the thyristor SCR2 to turn on, so as to control the trigger capacitor C2 to discharge to the primary side of the pulse transformer T1. The turn ratio of the primary and secondary coils of the pulse transformer T1 is 1:39. The high-voltage output end of the secondary side of the pulse transformer T1 is connected to one end of the DC-blocking capacitor C3. The capacitance of C3 is 2.6 nF. The connection line of the other end of the DC-blocking capacitor C3 is divided into two paths. One path is connected to one end of the saturable inductor L, and the other path is led out as the high-voltage output end of the pulse voltage of the pulse voltage generating circuit 9, which is connected to the trigger electrode 3 of the capillary discharge jet device 19; the other end of the wave-adjusting inductor L is connected to one end of the trigger circuit current-limiting resistor R. The other end of the trigger circuit current-limiting resistor R is divided into two paths. One path is connected to the low-voltage output end of the secondary side of the pulse transformer T1, and the other path is led out as the low-voltage output end of the pulse voltage of the pulse voltage generating circuit 9, which is connected to the front flange cover 5 of the capillary jet device 19.

[0095] As Figure 5 shown, in the pulse current generating circuit 10, the typical charging voltage of the energy storage capacitor C1 is 2 kV. The capacitance value of the energy storage capacitor is adjustable from 140 μF to 560 μF, and the stored energy is 280 J - 1120 J. Its high-voltage and low-voltage ends are respectively connected to the high-voltage and low-voltage output ends of the LC series resonance charging circuit 17. Before the single-shot discharge starts, the energy storage capacitor C1 is quickly charged to the preset voltage. The high-voltage end of the energy storage capacitor C1 is connected to the anode of the thyristor SCR1, and the thyristor SCR1 and the diode VT1 are connected in antiparallel, where the anode of the thyristor SCR1 is connected to the cathode of the diode VT1, and the cathode of the thyristor SCR1 is connected to the anode of the diode VT1; the cathode end of the thyristor SCR1 is led out as the high-voltage output end of the pulse current generating circuit 10 and is connected to the anode 2 of the capillary jet device 19. The trigger signal 22 of the thyristor trigger circuit 16 is connected to the gate of the thyristor SCR1 to control the thyristor SCR1 to turn on and control the discharge of the energy storage capacitor C1. The connection line of the low-voltage side of the energy storage capacitor C1 is led out as the low-voltage output end of the pulse current generating circuit 10 and is connected to the front flange cover 5 of the capillary jet device 19.

[0096] As Figure 6As shown, in the LC series resonance charging circuit 17, the turns ratio of the primary and secondary sides of the transformer T is 6:48. In its primary part, the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 in the N-channel IGBT module are connected in a bridge configuration, where each IGBT module S i is anti-parallel connected to the diode D i . The collector of the IGBT module S i is connected to the cathode of the diode D i . The emitter of the IGBT module S i is connected to the anode of the diode D i (i = 1, 2, 3, 4). The voltage of the DC power supply U2 is 360V and the power is 12kW. The high-voltage end is connected to the collectors of the first IGBT module S1 and the third IGBT module S3. The emitter of the first IGBT module S1 is connected to the collector of the second IGBT module S2. The emitter of the third IGBT module S3 is connected to the collector of the fourth IGBT module S4. The emitters of the third IGBT module S3 and the fourth IGBT module S4 are connected together and commonly connected to the low-voltage side of the DC power supply U2. The gates of the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 are respectively connected to the all-hardware drive controller 24, and the all-hardware drive controller 24 respectively sends control signals to the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 to control their turn-on and turn-off. The emitter of the first IGBT module S1 is connected to one end of the resonant inductor L r . The other end of the resonant inductor L r is connected to one end of the resonant capacitor C r . The other end of the resonant capacitor C rThe other end is connected to one end of the primary coil of transformer T, and the other end of the primary coil of transformer T is connected to the emitter of the third IGBT module S3. The secondary side of transformer T is connected to a diode full-bridge rectifier circuit composed of the first diode D5, the second diode D6, the third diode D7, and the fourth diode D8. The anode of the first diode D5 is connected to the cathode of the second diode D6, and the anode of the third diode D7 is connected to the cathode of the fourth diode D8. One end of the secondary side of transformer T is commonly connected to the anode of the first diode D5 and the cathode of the second diode D6, and the other end of the secondary side of transformer T is commonly connected to the anode of the third diode D7 and the cathode of the fourth diode D8. The cathode of the first diode D5 and the cathode of the third diode D7 are connected and connected to one end of the filter inductor L2. The other end of the filter inductor L2 is connected to the collector of the fifth IGBT module S5. The emitter of the fifth IGBT module S5 is connected to the high-voltage output terminal of the LC series resonance charging circuit. The gate of the fifth IGBT module S5 is connected to the all-hardware drive controller 24. The all-hardware drive controller 24 controls the on and off of the fifth IGBT module S5 to control the on and off of the output circuit; the negative output terminal of the diode full-bridge rectifier circuit is connected to the low-voltage output terminal of the LC series resonance charging circuit module. A resistor divider 26 composed of the first resistor R1 and the second resistor R2 is connected in parallel between the high- and low-voltage output terminals of the LC series resonance charging circuit. One end of the first R1 is connected to the high-voltage output terminal, and the other end is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to the low-voltage output terminal and is connected to the anodes of the second diode D6 and the fourth diode D8; the voltage signal divided by the resistor divider 26 is input into the opto-isolation module 25 and is input into the all-hardware drive controller 24 after signal isolation; at the same time, the control signal 23 from the control system 18 controls the operation of the all-hardware drive controller 24 to control the start and stop of the PWM signals driving the bridge arms of the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 and the on and off of the fifth IGBT module S5.

[0097] Among them, an energetic doped working fluid block 1 is used in the capillary jet device 19, and its structure is as Figure 3 shown, and its preparation method is:

[0098] By mixing, pressing, sintering, and machining active metal powders such as aluminum powder and boron powder with PTFE powder to make a modified energetic working fluid. Taking the doped aluminum powder as an example, the specific preparation process of the energetic doped working fluid block 1 is as Figure 17 shown:

[0099] Mix aluminum powder with a size ranging from nanometers to micrometers and polytetrafluoroethylene powder with a micron particle size in a certain proportion. The aluminum powder accounts for 3% - 26% of the total powder mass. Other materials can be added, including doping part of alumina powder to improve the mechanical properties of the energetic working medium block, or adding a small amount of ammonium perchlorate (AP) powder to increase the chemical energy released by the reaction. The reaction equation between aluminum powder and polytetrafluoroethylene at high temperature is:

[0100] 4Al + 3C2F4 = 4AlF3 + 6C + Q1

[0101] Where Q1 is the heat released by the reaction, and the energy release can reach 14.9 kJ / g.

[0102] Place all the powders in a blender and shear-mix them evenly, then put them into a cylindrical hydraulic press mold with a hole in the middle. The filling is completed in one go, and it is kept under a pressure of 20 Mpa for 5 minutes. Then, slowly and gradually relieve the pressure of the hydraulic press to make a cylindrical blank with a through-hole in the middle. Let it stand for 24 hours to eliminate internal stress, and then sinter it in a tube furnace under an argon protection atmosphere. Set the temperature curve as Figure 16 shown: First, heat it at a heating rate of 50 degrees Celsius per hour to 380 degrees Celsius, hold for 6 hours, then cool it at a cooling rate of 50 degrees Celsius per minute to 327 degrees Celsius, hold for 2 hours, and then cool it to room temperature at a cooling rate of 50 degrees Celsius per minute. This can not only ensure that the polytetrafluoroethylene is fully melted and the powder is evenly mixed, but also ensure the crystallinity of the sample after cooling to ensure sufficient mechanical strength. Finally, through machining, a capillary channel 12 is machined at the axial center position of the working medium block, with a diameter range of 1 - 10 mm and a length range of 10 - 100 mm, for inserting the anode 2. And a cylindrical channel 14 with a diameter of 1 - 5 mm is vertically machined inward on the side of the cylindrical working medium block. The depth of the through-hole is equal to the radius of the capillary working medium block, and the distance from the position of the through-hole to one bottom surface of the cylindrical working medium block is 25 mm. For inserting the trigger electrode 3 in the middle.

[0103] Using a repetitive pulsed plasma jet generation system with an energetic doped working medium, it can repeatedly generate plasma jets at a set frequency. Its working timing diagram is as Figure 12 shown, and its working process is:

[0104] During each cycle T, the control system 18 controls the DC power supply U2 in the LC series resonance charging circuit 17 to start charging by sending a charging start signal 23 to the all-hardware drive controller 24 in the LC series resonance charging circuit 17; the control system inputs a trigger plasma jet opening signal 20 to the thyristor trigger circuit 16 at a set frequency to trigger a single capillary discharge to draw out the plasma jet. When the opening signal 20 is sent, the charging start signal 23 is interrupted for 580 μs to ensure that after the plasma jet extraction is completed, the control system then controls the LC series resonance charging circuit to start working again. Each cycle of generating the plasma jet can be divided into two steps: energy storage system charging and pulse discharge to generate the plasma jet:

[0105] 1) Energy storage system charging process: The control system 18 controls the LC series resonance charging circuit 17 to start working by sending a charging start signal 23 to the all-hardware drive controller 24 in the LC series resonance charging circuit 17. This signal lasts for the entire discharge cycle time T and stops when the thyristor control opening signal 20 is triggered and sent. The all-hardware drive controller 24 inputs complementary PWM drive signals with a duty cycle of 25% to a group consisting of the first IGBT module S1 and the third IGBT module S3, and a group consisting of the second IGBT module S2 and the fourth IGBT module S4. The frequency of the PWM drive signal is the same as the circuit resonance period, set to 18.3 kHz, to control the bridge arms to conduct alternately. The DC power provided by the DC power supply U2 is converted into AC power, stepped up by the transformer T, and then converted back into DC power by the diode full-bridge rectifier circuit to charge the energy storage capacitor C1 to a maximum high voltage of 2000V. The resistor voltage divider 26 connected to the output terminal, with a voltage division ratio of 1334:1, collects the voltage of the energy storage capacitor C1, divides the voltage of the energy storage capacitor C1 of 0 - 2000V into a voltage signal of approximately 0 - 1.5V, and inputs it into the drive controller 24 through the opto-isolation module 25. It is compared with the set charging voltage through the operational amplifier circuit, and the gate circuit group determines whether the voltage of the energy storage capacitor C1 reaches the preset voltage. When the voltage of the energy storage capacitor C1 reaches the set charging voltage, the drive controller stops inputting the drive PWM signal to S1 - S4 and controls S5 to turn off the charging circuit. In the system of the present invention, when the capacitance of the energy storage capacitor C1 in the LC series resonance charging circuit 17 is 140 μF in the pulse current generating circuit, it takes about 32.5 ms to charge it to 2000V. The voltage waveform of the energy storage capacitor C1 during the charging process is as Figure 18 shown.

[0106] 2) Process of generating plasma jet by pulsed discharge: When a repetition frequency period T elapses and the trigger discharge moment is reached, the control system 18 transmits a trigger signal 20 for controlling the thyristor to turn on to the thyristor trigger circuit 16. The duration of this signal is 20 μs. At the same time, the charging start signal 23 is stopped for 580 μs, causing the LC series resonance charging circuit to stop working during the whole process of extracting the capillary discharge plasma jet; The thyristor trigger circuit 16 transmits a second trigger signal 22 to the thyristor SCR1 in the pulsed current generating circuit 10 to control its conduction, applying the voltage of the energy storage capacitor C1 between the anode 2 and the front flange cover plate 5. During the discharge process, the front flange cover plate 5 serves as the cathode; After a delay of 5 μs, the thyristor trigger circuit 16 inputs a first trigger signal 21 to the thyristor SCR2 in the pulsed voltage generating circuit to control its conduction, applying a trigger high-voltage pulse to the trigger electrode 3. Its amplitude is 39 kV and the pulse width is 500 ns, inducing surface discharge to occur in the trigger channel 15 between the end of the anode 2 and the end of the trigger electrode 3;

[0107] The surface discharge in the trigger channel 15 forms an arc, ablating the capillary wall material of the trigger channel 15 to form a high-conductivity plasma that moves towards the front flange cover plate 5 serving as the cathode. When the plasma reaches the cathode front flange cover plate 5, the capillary channel between the anode 2 and the cathode front flange cover plate 5 is filled with high-conductivity plasma. The channel between the anode 2 and the cathode front flange cover plate 5, that is, the high-voltage output terminal and the low-voltage output terminal of the pulsed current generating circuit 10, is short-circuited. A discharge loop is formed from the high-voltage output terminal of the pulsed current generating circuit 10 - anode 2 - arc in the capillary channel 12 - cathode front flange cover plate 5 - low-voltage output terminal of the pulsed current generating circuit 10. The electrical energy stored in the energy storage capacitor in the pulsed current generating circuit 10 starts to be released through the arc load in the capillary channel 12. The high-temperature arc radiation energy ablates the energy-doped working medium material on the inner wall of the capillary channel 12 of the solid working medium to form a high-temperature and high-pressure plasma. The active components such as aluminum powder in the plasma react chemically with the polytetrafluoroethylene (PTFE) component to release energy, further increasing the internal energy of the plasma jet. The inner wall material of the capillary channel 12 of the energy-doped working medium block 1 continuously undergoes phase change and decomposition and enters the interior of the capillary channel 12, increasing the internal pressure of the cavity, causing the plasma to continuously move towards the cathode nozzle 6 under the action of the pressure gradient and finally ejecting outward to generate a high-temperature and high-density plasma jet 13; The voltage-current waveform and timing of single capillary discharge using aluminum-based doped polytetrafluoroethylene working medium are as Figure 11 shown. At the charging voltage of 2000 V of the energy storage capacitor C1 and the energy storage of 280 J, the single discharge voltage-current waveform is as Figure 7 shown. The peak value of the discharge current is about 8 kA. From the breakdown moment t0 of the trigger gap 15 to the moment t1 when the arc current in the capillary channel increases significantly, the discharge delay t of the plasma jet trigger process dIt is about 104 μs, and the entire discharge process is about 165 μs.

[0108] The test system of the present invention is suitable for the ignition condition of the propellant under the action of the repetitive frequency capillary discharge plasma jet, and can realize the diagnosis of the plasma parameters of the repetitive frequency plasma jet, as well as the temperature, pressure, jet morphology and spectral analysis during the ignition and combustion processes of the propellant during the repetitive frequency ignition process. The propellant can be in the form of gas, liquid or solid. The pulse voltage signal of the trigger electrode 3 is used to synchronize the acquisition time of each signal.

[0109] The test system of the present invention can realize the experimental diagnosis of the parameters of any pulse plasma jet in a repetitive frequency sequence, and obtain electrical parameters such as the voltage of the trigger electrode 3, the voltage of the anode 2, and the arc channel current during the discharge process. The development morphology of the plasma jet is collected by the high-speed camera 33, and the emission spectrum of the capillary discharge plasma jet 13 is collected by the spectrometer 32, and the plasma composition, plasma electron temperature and electron density can be obtained. In addition, during the repetitive frequency ignition test, the pressure in the combustion chamber is collected by the pressure sensor 34, and the temperature during the ignition process of the propellant is collected by the thermocouple 43. The plasma ignition characteristic test includes the diagnosis of the parameters of the repetitive frequency capillary discharge plasma jet to obtain a multi-dimensional characterization of the plasma jet ignition ability; and the research on the ignition process of the propellant under the action of the repetitive frequency plasma jet. The process of the ignition characteristic test is as follows:

[0110] Before the test, electrical, optical and pressure measurement and control equipment are arranged: the voltage of the trigger electrode 3 is measured by the first high-voltage probe 28, the voltage of the anode 2 is measured by the second high-voltage probe 29, the arc discharge current in the capillary channel 12 is measured by the Rogowski coil 27, and the high-speed camera 33 is used to photograph the internal plasma flow of the test cavity 44 and the ignition process of the propellant through the side quartz glass 36 of the test cavity 44. The axis direction of the lens of the high-speed camera 33 is perpendicular to the axis direction of the test cavity 44. The axis direction of the collimating mirror 30 is perpendicular to the axis direction of the test cavity 44, and the light emitted inside the cavity is collected through the quartz glass 36 and transmitted to the spectrometer 32 through the optical fiber 31 to analyze the plasma spectrum. In addition, the current pulse signal 40 collected by the Rogowski coil 27 is input into the counter 42, and the counting number N of the counter is preset. When the counter receives the rising edge of each current pulse signal, the counting of the counter is incremented by one. When the counting reaches N, the counter 42 sends a trigger signal 41 to the spectrometer 32 and the high-speed camera 33, and the high-speed camera 33 and the spectrometer 32 start to synchronously collect signals. The pressure sensor 34 collects the pressure change in the test cavity during the ignition process of the propellant through the pressure measuring hole 35 opened on the side of the test cavity 44.

[0111] Before the experiment, in the control system 18, the repetitive frequency discharge frequency and the number of discharge pulses are set. The charging voltage of the energy storage capacitor C1 is set.

[0112] In the counter 42, the counting quantity N is set, that is, when the Nth discharge current pulse 40 is collected, a trigger signal 41 is output. Connect the output terminal of the counter trigger signal to the high-speed camera 33 and the spectrometer 32. Set the exposure time of the high-speed camera to be generally less than 1 μs, the frame rate to be higher than 50000 fps, the acquisition time of the high-speed camera to be not less than 2 s, and the spectral exposure time of the spectrometer to be less than 50 μs.

[0113] Connect the Rogowski coil 27, voltage probe 28, and voltage probe 29 to the oscilloscope 45, and set the voltage division ratio of each channel to be the same as that of each probe. Set the trigger mode of the oscilloscope 45 to use the rising edge single-shot trigger of the voltage signal 46 from the high-voltage probe 28; connect the pressure sensor 34 and the thermocouple 43 to the acquisition card 50, and set the trigger mode of the acquisition card 50 to use the rising edge single-shot trigger of the voltage signal 46 from the high-voltage probe 28. Set the sampling rate of the current signal 40, trigger electrode voltage signal 46, and anode voltage signal 47 of the oscilloscope to be not less than 10 MSa / s, and the recording time to be not less than 2 s; set the sampling rate of the pressure signal 48 in the sampling card 50 to be not less than 1 MSa / s, and the sampling rate of the temperature signal 49 of the thermocouple 43 to be not less than 1 kSa / s, and the recording time to be not less than 2 s.

[0114] The operation methods of the two processes of the diagnosis of the parameters of the repetitive-pulse capillary discharge plasma jet and the ignition process of the propellant under the action of the repetitive-pulse plasma jet are as follows:

[0115] (1) During the diagnosis of the parameters of the repetitive-pulse capillary discharge plasma jet, open the pressure control valve 38 to connect the inside of the test chamber 44 to the outside atmosphere, and take out the propellant 37 and the thermocouple 43 in the test chamber.

[0116] Start the repetitive-pulse charge and discharge. The control system 18 controls the LC series resonance charging circuit 17 to charge the energy storage capacitor C1 in the pulse current generation circuit 10 with constant current, and charge the energy storage capacitor C1 to the preset voltage within dozens of milliseconds. When the trigger discharge time is reached, the control system 18 controls the thyristor trigger circuit 16 to trigger the thyristor SCR2 in the pulse voltage generation circuit 9 and the thyristor SCR1 in the pulse current generation circuit 10. The pulse voltage generation circuit 9 outputs a high-amplitude pulse voltage to break down the trigger gap 15, and the voltage signal collected by the high-voltage probe 28 triggers the oscilloscope 45 and the acquisition card 50. The energy of the energy storage capacitor C1 in the pulse current generation circuit 10 is discharged through the arc channel in the capillary channel 12 of the jet device 19. The wire passing through the Rogowski coil 27 carries a pulse current of thousands of amperes, and the output current signal 40 is measured by the Rogowski coil 27.

[0117] The current signal 40 is input into the counter 42, and the count of the counter is incremented by one. Each time a discharge is triggered, the count of the counter is incremented by one. When the set count number N is reached, the counter 42 sends a trigger signal to the high-speed camera 33 and the spectrometer 32. The timing of the pulsed current signal input and the trigger signal output of the counter 42 is as Figure 14 shown. After being triggered, the high-speed camera 33 starts to collect the jet development morphology during the discharge process, and the spectrometer 32 collects the plasma jet spectrum.

[0118] When a capillary discharge ends and the set number of discharges is not reached, the control system 18 charges the energy storage capacitor C1 rapidly again, and so on. The oscilloscope 45 records the voltage and current waveforms of the entire discharge process, as Figure 15 shown.

[0119] (2) In the experiment on the ignition process of the propellant under the action of the repetitive plasma jet, the propellant 37 is placed inside the test cavity. The propellant 37 can be in the form of gas, solid or liquid. The thermocouple 43 is inserted into the test cavity 44. The pressure control valve 38 is closed, and the pressure threshold P0 for its opening is set to control the pressure inside the test cavity 44 during the combustion process of the propellant. The pressure threshold P0 is set to be consistent with the working pressure of the propulsion system, generally not higher than 15 MPa.

[0120] Start the repetitive charge and discharge. The oscilloscope 45 collects the voltage and current waveforms during the discharge process. The high-speed camera 33 takes pictures of the process of the plasma jet 13 acting on the propellant 37 and the ignition and combustion process of the propellant. The spectrometer 32 collects the spectra of the above processes. The pressure sensor 34 collects the pressure in the test cavity 44 during the ignition process of the propellant. The thermocouple 43 collects the temperature data in the test cavity 44 during the ignition process of the propellant.

[0121] The data processing method after the experiment is as follows:

[0122] In the measurement and processing of electrical parameters, the discharge delay t d is calculated in the following way: For each capillary discharge in the repetitive sequence, the time t1 when the current i starts to rise collected from the Rogowski coil 27 is subtracted from the time t0 when the voltage u trig peak value corresponds to the breakdown of the trigger gap, as Figure 7 indicated by the label in.

[0123] t d = t1 - t0 (1)

[0124] The arc channel resistance R arc is calculated according to the following formula:

[0125]

[0126] where u anoderepresents the anode voltage measured by the high-voltage probe 29, and i represents the current measured by the Rogowski coil 27. Calculate the arc channel resistance during the discharge process as Figure 8 shown below.

[0127] The power deposition P in the arc channel arc is calculated according to the following formula:

[0128] P arc = |u anode i| (3)

[0129] The energy deposition E in the arc channel arc is calculated according to the following formula:

[0130]

[0131] where t1 is the moment when the current i starts to rise collected by the Rogowski coil 27, and t2 is the moment when the current i drops to 0 collected by the Rogowski coil 27. Calculate the power deposition and energy deposition in the arc channel as Figure 9 shown below.

[0132] In the measurement and processing of optical parameters, the morphology and evolution process of the plasma jet are photographed by the high-speed camera 33, and the development time sequence of the plasma jet is as Figure 10 shown below.

[0133] The wavelength of the characteristic spectral line of the emission spectrum collected by the spectrometer 32 is compared with the wavelength of the atomic spectral line emission spectrum database. When the wavelength position of the spectral line collected by the spectrometer is consistent with the spectral line position of a certain element component in the database, it is considered that the element component exists in the plasma jet; the spectrum in the range of 510 - 525 nm of the plasma jet and the position of the Cu I spectral line are as Figure 11 shown below. The electron temperature of the plasma jet can be calculated by the Boltzmann slope method: as shown in formula (5):

[0134]

[0135] In the formula: I g —— spectral line emission intensity; λ —— wavelength / nm; g —— statistical weight of the upper energy level; A —— spontaneous emission coefficient / s -1 ; E exc —— wave number of the excitation energy of the high energy state / cm -1 ; h —— Planck constant; c —— speed of light in vacuum / m·s -1 ; n m —— atomic density; z —— temperature-dependent partition function.

[0136] Select several spectral lines of a certain type of particle, and find the corresponding spectral line emission intensity I g in the measured spectrum. According to the known g, A, Eexc With the measured I g , make an E exc -lg(I g λ) / (gA) scatter plot and fit a straight line. The jet electron temperature T e = -0.625 / k can be calculated from the slope k of the straight line. At the same time, since only the slope needs to be calculated, the spectral line emission intensity is calculated using the relative intensity.

[0137] In the experiment of the ignition process of the propellant under the action of a repetitive plasma jet, it is necessary to measure the propellant temperature and the pressure in the test chamber during the ignition process of the propellant. The oscilloscope 45 and the acquisition card 50 are both triggered once by the rising edge of the voltage signal of the first high-voltage probe 28 to achieve time synchronization of the temperature signal 49, the pressure signal 48, the current signal 40, the trigger electrode voltage signal 46, and the anode voltage signal 47. The temperature signal 49 and the pressure signal 48 are used to represent the ignition moment and the plasma ignition efficiency. Since a large amount of high-temperature and high-pressure gas is released during the ignition of the propellant, the internal pressure of the test chamber 44 will increase significantly. The ignition delay t fd is defined as starting from the trigger moment t0 of the oscilloscope 45 and the acquisition card 50 by the first voltage pulse signal of the trigger electrode 3 collected by the first high-voltage probe 28, to the moment t 10％ when the pressure sensor 34 in the test chamber 44 collects the pressure signal 48 and starts to rise to 10% of the maximum pressure;

[0138] t fd = t 10％ - t0 (6)

[0139] The improvement effect of the plasma jet on the ignition efficiency of the propellant is characterized by the pressure rise rate. The pressure rise rate r p is defined as the pressure change ΔP = P 90％ - P 10％ when the pressure rises from 10% to 90% of the maximum value during ignition divided by the time Δt = t 90％ - t 10％ .

[0140]

[0141] The schematic diagrams of the definitions of the ignition delay and the pressure rise rate are as Figure 13 shown.

[0142] The present invention designs a test system for the ignition characteristics of repetitive plasma jets for a propulsion system. Aiming at the ignition conditions of propellants under the action of repetitive capillary discharge plasma jets, the propellants can be in the form of gas, liquid or solid. To characterize the ignition efficiency of repetitive plasma jets on propellants, the system controls the pressure in the test chamber through a controllable valve to simulate the operating pressure of the engine. By introducing a counter, electrical and optical diagnostics of the parameters of any plasma jet in the repetitive discharge sequence are realized, as well as the measurement of the propellant temperature and the test chamber pressure during the ignition process of the propellant under the action of repetitive jets. The electrical parameters of capillary discharge and the temperature and pressure parameters of propellant combustion are synchronized in time through the trigger electrode voltage, so as to achieve the purpose of multi-dimensional characterization of the ignition efficiency of solid propellants under the action of repetitive capillary discharge plasma jets.

Claims

1. A test system for the ignition characteristics of a repetitive pulsed plasma jet for a propulsion system, characterized in that: It includes a repetitive-pulse plasma jet generation system using an energetic doped working fluid, a test chamber, and diagnostic equipment; the repetitive-pulse plasma jet generation system using an energetic doped working fluid includes a capillary jet device (19), a pulse voltage generation circuit (9), a pulse current generation circuit (10), a thyristor trigger circuit (16), an LC series resonance charging circuit (17), and a control system (18); the diagnostic equipment includes a first high-voltage probe (28), a second high-voltage probe (29), a Rogowski coil (27), a collimating mirror (30), an optical fiber (31), a spectrometer (32), a high-speed camera (33), a pressure sensor (34), a thermocouple (43), an oscilloscope (45), and a data acquisition card (50). In the capillary jet device (19) capable of repetitive operation using an energy-enhanced and modified working fluid, the energetic doped working fluid block (1) is made of active metal powders from the nanoscale to the micron scale, mixed with polymer powders, pressed, sintered, and machined into a modified energetic working fluid, and a capillary channel (12) is machined at the axis, and a cylindrical channel (14) is machined on the side to communicate with the capillary channel (12). The energetic doped working fluid block (1) is coaxially installed inside the outer shell (8); the front part of the outer shell (8) is connected to the front flange cover plate (5), and the rear part is connected to the rear flange cover plate (7); the front flange cover plate (5) is coaxially machined with an expanding cathode nozzle (6); the anode (2) is inserted into the capillary channel (12) from the rear of the energetic doped working fluid block (1), and the trigger electrode (3) is inserted from the cylindrical channel (14) on the side of the energetic doped working fluid block (1), dividing the capillary channel (12) between the end of the anode (2) and the front flange cover plate (5) into two parts: the part between the anode (2) and the trigger electrode (3), called the trigger channel (15), and the part between the trigger electrode (3) and the front flange cover plate (5); insulators (4) are installed outside the anode (2) and the trigger electrode (3) to achieve electrical isolation from the outer shell, and the limit screw (11) is installed outside the insulator (4) and fixedly connected to the outer shell (8). The connection relationships of each module in the repetitive - pulse plasma jet generation system using an energetic - doped working medium are as follows: The high - voltage output terminal of the pulse voltage generation circuit (9) is connected to the trigger electrode (3) of the capillary jet device (19), and the low - level output terminal is connected to the front flange cover plate (5) of the capillary jet device (19); The high - voltage output terminal of the pulse current generation circuit (10) is connected to the anode (2) of the capillary jet device (19), and the low - voltage output terminal is connected to the front flange cover plate (5) of the capillary jet device (19). The front flange cover plate (5) of the capillary jet device (19) is grounded through a ground wire; The high - voltage output terminal of the LC series - resonance charging circuit (17) is connected to the high - voltage end of the energy - storage capacitor C1 in the pulse current generation circuit (10), and the low - voltage output terminal is connected to the low - voltage end of the energy - storage capacitor C1 in the pulse current generation circuit (10) to achieve rapid charging of the energy - storage capacitor; The two drive - voltage output terminals of the thyristor trigger circuit (16) are respectively connected to the thyristor SCR2 in the pulse voltage generation circuit (9) to send a trigger signal (21), and to send a trigger signal (22) to the thyristor SCR1 in the pulse current generation circuit (10) to control the turn - on of the two thyristors; The control system (18) is connected to the LC series - resonance charging circuit (17) and the thyristor trigger circuit (16) through optical fibers. According to the set frequency, it sends a charging start signal (23) to the LC series - resonance charging circuit (17) and a thyristor trigger control turn - on signal (20) to the thyristor trigger circuit (16). The front flange cover plate (5) of the capillary jet device (19) is connected to one end of the test chamber (44). The test chamber (44) is a coaxial cylindrical structure with a hollow interior. Propellant (37) is placed inside the test chamber (44) to simulate the ignition and combustion conditions of the propellant inside the engine of the propulsion system under plasma conditions; The other end of the test chamber (44) is connected to the pressure control valve (38). By presetting the internal pressure P0 of the chamber to be consistent with the actual engine conditions, when the propellant ignites during the test, if the internal pressure of the test chamber (44) is lower than the preset pressure P0, the pressure control valve (38) closes. After the internal pressure is higher than the preset pressure P0, it opens to release pressure, and closes again when the internal pressure of the test chamber is lower than the preset pressure P0, so as to repeatedly control the internal pressure of the test chamber (44) to be consistent with the preset pressure P0; Two quartz observation windows (36) are opened on the side of the test chamber (44) to observe the internal plasma flow and combustion process; And a pressure - measuring hole (35) is used to connect a pressure sensor (34) to measure the internal pressure of the test chamber. In terms of the connection of peripheral experimental equipment, the wire connecting the anode (2) of the capillary jet device (19) to the high-voltage output terminal of the pulsed current generation circuit (10) passes through the Rogowski coil (27) to measure the pulsed discharge current of the capillary discharge arc channel. The measured current signal (40) is divided into two paths. One path enters the first channel of the oscilloscope (45) to be collected, and the other path enters the counter (42). When the preset count is reached, the counter (42) sends a trigger signal (41) to the high-speed camera (33) and the spectrometer (32) to collect the development morphology and spectrum of a specific plasma jet in the repetitive discharge sequence. The high-voltage terminal of the first high-voltage probe (28) is connected to the trigger electrode (3) of the capillary jet device (19), and the grounded terminal is connected to the housing (8) to collect the voltage of the trigger electrode (3). The measured trigger electrode voltage signal (46) is divided into two paths. One path enters the second channel of the oscilloscope (45) to be collected, and the other path is used as a trigger signal to access the acquisition card (50). The high-voltage terminal of the second high-voltage probe (29) is connected to the anode (2) of the capillary jet device (19), and the grounded terminal is connected to the rear flange cover (7) to collect the voltage of the anode (2). The measured anode voltage signal (47) enters the third channel of the oscilloscope (45). The high-speed camera (33) takes pictures of the development morphology of the plasma jet and the propellant ignition process inside the test chamber (44) through the quartz glass window (36). The axis direction of the high-speed camera (33) lens is perpendicular to the axis direction of the test chamber (44). The collimating mirror (30) collects the plasma jet and ignition combustion light inside the test chamber (44) through the quartz glass window (36) and enters the spectrometer (32) through the optical fiber (31) to analyze the spectrum of the plasma jet and ignition process. The pressure sensor (34) measures the internal pressure of the test chamber (44) during the discharge and ignition processes through the pressure measurement hole (35), and the pressure signal (48) is collected by the acquisition card (50). The thermocouple (43) is inserted into the test chamber (44) to measure the temperature of the propellant during the ignition process, and the temperature signal (49) is collected by the acquisition card (50). For the study of the characteristics of plasma jets in open space, the propellant (37) and the thermocouple (43) are not placed inside the test chamber (44), and the pressure control valve (38) is opened to connect the inside of the test chamber (44) to the external atmospheric environment. For the study of propellant ignition under the action of plasma jets, the propellant (37) and the thermocouple (43) are placed inside the test chamber (44), and the pressure control valve (38) works normally to maintain the control of the internal pressure of the chamber.

2. The test system for the ignition characteristics of repetitive pulsed plasma jets for a propulsion system according to claim 1, characterized in that: In the pulse voltage generating circuit (9), the high-voltage terminal of the DC power supply U1 is connected to one end of the charging current-limiting resistor R C2 One end of the charging current-limiting resistor R C2 The other end is divided into two paths. One path is connected to one end of the trigger capacitor C2 as the high-voltage terminal of the trigger capacitor C2, and the other path is connected to the anode of the thyristor SCR2. The other end of the trigger capacitor C2, i.e., the low-voltage terminal, is divided into two paths. One path is connected to the low-voltage terminal of the DC power supply U1, and the other path is connected to one end of the primary coil of the pulse transformer T1. The cathode of the thyristor SCR2 is connected to the other end of the primary coil of the pulse transformer T1. The antiparallel diode VT2 is connected in parallel with the primary coil of the pulse transformer T1, its anode is connected to the low-voltage side of the trigger capacitor C2, and its cathode is connected to the cathode of the thyristor SCR2. The first trigger signal (21) of the thyristor trigger circuit (16) controls the gating of the thyristor SCR2 to control the discharge of the pulse capacitor C2 to the primary side of the pulse transformer T1. The high-voltage output terminal of the secondary side of the pulse transformer T1 is connected to one end of the DC-blocking capacitor C3. The other end of the DC-blocking capacitor C3 is led out and divided into two paths. One path is connected to one end of the saturable inductor L, and the other path is led out as the high-voltage output terminal of the pulse voltage of the pulse voltage generating circuit (9), which is connected to the trigger electrode (3) of the capillary discharge jet device (19). The other end of the wave-shaping inductor L is connected to one end of the trigger loop current-limiting resistor R. The other end of the trigger loop current-limiting resistor R is divided into two paths. One path is connected to the low-voltage output terminal of the secondary side of the pulse transformer T1, and the other path is led out as the low-voltage output terminal of the pulse voltage of the pulse voltage generating circuit (9), which is connected to the front flange cover plate (5) of the capillary jet device (19).

3. A test system for the ignition characteristics of a repetitive pulsed plasma jet for a propulsion system according to claim 1, characterized in that: In the pulsed current generating circuit (10), the high and low voltage terminals of the energy storage capacitor C1 are respectively connected to the high and low voltage output terminals of the LC series resonance charging circuit (17). Before the start of a single discharge, the energy storage capacitor C1 is quickly charged to a preset voltage. The high voltage terminal of the energy storage capacitor C1 is connected to the anode of the thyristor SCR1, and the thyristor SCR1 and the diode VT1 are connected in antiparallel, where the anode of the thyristor SCR1 is connected to the cathode of the diode VT1, and the cathode of the thyristor SCR1 is connected to the anode of the diode VT1. The cathode terminal of the thyristor SCR1 is led out as the high voltage output terminal of the pulsed current generating circuit (10) and is connected to the anode (2) of the capillary jet device (19). The second trigger signal (22) of the thyristor trigger circuit (16) is connected to the gate of the thyristor SCR1 to control the opening of the thyristor SCR1 and the discharge of the energy storage capacitor C1. The connection wire of the low voltage side of the energy storage capacitor C1 is led out as the low voltage output terminal of the pulsed current generating circuit (10) and is connected to the front flange cover plate (5) of the capillary jet device (19).

4. A test system for the ignition characteristics of a repetitive frequency plasma jet for a propulsion system according to claim 1, characterized in that: In the LC series resonant charging circuit (17), for the primary part of the transformer T: The first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 in the N-channel IGBT module are connected in a bridge configuration, where each IGBT module S i is anti-parallel connected with the diode D i The collector of the IGBT module S i is connected to the cathode of the diode D i The emitter of the IGBT module S i is connected to the anode of the diode D i where i = 1, 2, 3, 4; The high-voltage terminal of the DC power supply U2 is connected to the collectors of the first IGBT module S1 and the third IGBT module S3. The emitter of the first IGBT module S1 is connected to the collector of the second IGBT module S2. The emitter of the third IGBT module S3 is connected to the collector of the fourth IGBT module S4. The emitters of the third IGBT module S3 and the fourth IGBT module S4 are connected together and commonly connected to the low-voltage side of the DC power supply U2; The gates of the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 are respectively connected to the all-hardware drive controller (24). The all-hardware drive controller (24) respectively sends control signals to the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4 to control their turn-on and turn-off; The emitter of the first IGBT module S1 is connected to one end of the resonant inductor L r One end of the resonant inductor L r The other end is connected to one end of the resonant capacitor C r One end of the resonant capacitor C r The other end is connected to one end of the primary coil of transformer T, and the other end of the primary coil of transformer T is connected to the emitter of the third IGBT module S3; the secondary side of transformer T is connected to a diode full-bridge rectifier circuit composed of the first diode D5, the second diode D6, the third diode D7 and the fourth diode D8. The anode of the first diode D5 is connected to the cathode of the second diode D6, and the anode of the third diode D7 is connected to the cathode of the fourth diode D8. One end of the secondary side of transformer T is commonly connected to the anode of the first diode D5 and the cathode of the second diode D6, and the other end of the secondary side of transformer T is commonly connected to the anode of the third diode D7 and the cathode of the fourth diode D8. The cathode of the first diode D5 and the third diode D7 are connected and connected to one end of the filter inductor L2. The other end of the filter inductor L2 is connected to the collector of the fifth IGBT module S5. The emitter of the fifth IGBT module S5 is connected to the high-voltage output terminal of the LC series resonance charging circuit. The gate of the fifth IGBT module S5 is connected to the all-hardware drive controller (24). The all-hardware drive controller (24) controls the on and off of the fifth IGBT module S5 to control the on and off of the output circuit; the negative output terminal of the diode full-bridge rectifier circuit is connected to the low-voltage output terminal of the LC series resonance charging circuit module. A resistor divider (26) composed of the first resistor R1 and the second resistor R2 is connected in parallel between the high- and low-voltage output terminals of the LC series resonance charging circuit. One end of the first R1 is connected to the high-voltage output terminal, and the other end is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to the low-voltage output terminal and is connected to the anodes of the second diode D6 and the fourth diode D8; the voltage signal divided by the resistor divider (26) is input into the opto-isolation module (25) and is input into the all-hardware drive controller (24) after signal isolation; at the same time, the control signal (23) from the control system (18) controls the operation of the all-hardware drive controller (24), controls the start and stop of the PWM signals for driving the bridge arms of the first IGBT module S1, the second IGBT module S2, the third IGBT module S3 and the fourth IGBT module S4, and the on and off of the fifth IGBT module S5.

5. A test system for the ignition characteristics of a repetitive pulsed plasma jet for a propulsion system according to claim 1, characterized in that: A repetitive pulsed plasma jet generating system using an energetic doped working medium, wherein the preparation method of the energetic doped working medium block (1) in the capillary jet device (19) is as follows: Mix nano- to micro-sized active metal powders and micron-sized polymer powders in a certain proportion. The active metal powders account for 3%-26% of the total powder mass, or doped with some active metal oxide powders to improve the mechanical properties of the energetic working medium block, or add a small amount of ammonium perchlorate powder to increase the chemical energy released by the reaction. Place all the powders in a blender and shear-mix them evenly, then put them into a cylindrical hydraulic press mold with a hole in the middle. The filling is completed in one go, pressurize and hold, then slowly and gradually relieve the pressure of the hydraulic press to make a cylindrical blank with a through hole in the middle. Let it stand to eliminate internal stress, and then sinter it in an argon protection atmosphere. First, heat it at a heating rate of 50 degrees Celsius per hour to 370-390 degrees Celsius, keep it warm for 2-6 hours, then cool it at a cooling rate of 50 degrees Celsius per minute to 327 degrees Celsius, keep it warm for 2 hours, and then cool it to room temperature at a cooling rate of 50 degrees Celsius per minute. Finally, through machining, the capillary channel (12) is machined at the axial center position of the working medium block, and a cylindrical channel (14) is vertically machined inward on the side of the cylindrical working medium block to communicate with the capillary channel (12).

6. The test system for the ignition characteristics of a repetitive pulsed plasma jet for a propulsion system according to claim 1, characterized in that: The propellant is in the form of gas, liquid or solid.

7. The working method of the pulsed plasma jet ignition characteristic test system for a propulsion system according to any one of claims 1 to 6, characterized in that: It includes two processes: the diagnosis of repetitive pulsed capillary discharge plasma jet parameters and the test of the ignition process of the propellant under the action of repetitive pulsed plasma jet. The specific working method is as follows: (1) During the diagnosis of repetitive pulsed capillary discharge plasma jet parameters, open the pressure control valve (38) to make the inside of the test chamber (44) communicate with the outside atmosphere. No propellant (37) and thermocouple (43) are placed in the test chamber. Start repetitive frequency charge and discharge. The control system (18) controls the LC series resonance charging circuit (17) to charge the energy storage capacitor C1 in the pulse current generating circuit (10) with a constant current, and charges the energy storage capacitor C1 to a preset voltage within dozens of milliseconds. When the trigger discharge time is reached, the control system (18) controls the thyristor trigger circuit (16) to trigger the thyristor SCR2 in the pulse voltage generating circuit (9) and the thyristor SCR1 in the pulse current generating circuit (10). The energy of the energy storage capacitor C1 in the pulse current generating circuit (10) is discharged through the arc channel in the capillary channel (12) of the jet device (19). The wire passing through the Rogowski coil (27) flows through a pulse current of thousands of amperes, and the Rogowski coil (27) measures and outputs a current signal (40). The current signal (40) is input into the counter (42), and the counter count is incremented by one. Each time a discharge is triggered, the counter count is incremented by one. When the set count number N is reached, the counter (42) sends a trigger signal to the high-speed camera (33) and the spectrometer (32). The high-speed camera (33) starts to collect the jet development morphology during the discharge process, and the spectrometer (32) collects the plasma jet spectrum. When a capillary discharge ends and the set number of discharges is not reached, the control system (18) charges the energy storage capacitor C1 quickly again, and so on. The oscilloscope (45) records the voltage and current waveforms of the entire discharge process. (2) In the experiment on the ignition process of the propellant under the action of the repetitive frequency plasma jet, close the pressure control valve (38), set the pressure threshold for its opening, control the pressure inside the test chamber (44) during the combustion process of the propellant, fix the propellant (37) inside the test chamber (44), and the thermocouple (43) measures the temperature in the test chamber (44). Start repetitive frequency charge and discharge. The oscilloscope (45) collects the voltage and current waveforms during the discharge process. The high-speed camera (33) takes pictures of the process of the plasma jet acting on the propellant (37) and the ignition and combustion process. The spectrometer (32) collects the spectra of the above processes. The pressure sensor (34) collects the pressure in the test chamber (44) during the ignition process of the propellant, and the thermocouple (43) collects the temperature change data in the test chamber (44) during the ignition process.

8. The working method according to claim 7, characterized in that: The data processing method after the experiment is as follows: In the measurement and processing of electrical parameters, the discharge delay time t d is calculated as follows: for each capillary discharge in the pulse repetition rate sequence, the time t1 when the current i starts to rise collected from the Rogowski coil (27) is subtracted from the time t0 when the voltage u trig peak value corresponds to the breakdown of the trigger gap; t d = t1 - t0 (1) Arc channel resistance R arc It is calculated according to the following formula: where u anode represents the anode voltage measured by the second high-voltage probe (29), and i represents the current measured by the Rogowski coil (27); Arc power deposition P arc It is calculated according to the following formula: P arc = |u anode i| (3) Arc channel energy deposition E arc Calculate according to the following formula: Where t1 is the moment when the current i collected by the Rogowski coil (27) starts to rise, and t2 is the moment when the current i collected by the Rogowski coil (27) drops to 0. In the measurement and processing of optical parameters, the plasma jet morphology and evolution process are photographed by the high-speed camera (33). The plasma jet components are compared by the emission spectral characteristic line wavelengths collected by the spectrometer (32) and the line wavelengths in the atomic spectral emission spectrum database. When the line wavelength position collected by the spectrometer is consistent with the line position of a certain element component in the database, it is considered that the element component exists in the plasma jet. The electron temperature of the plasma jet is calculated by the Boltzmann slope method: as shown in formula (5): In the formula: I g —— Spectral line emission intensity; λ —— Wavelength / nm; g —— Statistical weight of the upper energy level; A —— Spontaneous emission coefficient / s -1 ; E exc —— Wave number of the excitation energy of the high energy state / cm -1 ; h —— Planck constant; c —— Speed of light in vacuum / m·s -1 ; n m —— Atomic density; z —— Temperature-dependent partition function; Select several spectral lines of a certain type of particle and find the corresponding spectral line emission intensities I in the measured spectrum g ; According to the known g, A, E exc and the measured I g , make a scatter plot of E<s exc -lg(I g λ) / (gA) and fit a straight line; Calculate the jet electron temperature T e =-0.625 / k from the slope k of the straight line; At the same time, since only the slope needs to be calculated, the spectral line emission intensity is calculated using the relative intensity 9. The working method according to claim 7, characterized in that: In the experiment of the propellant ignition process under the action of a repetitive plasma jet, it is necessary to measure the propellant temperature and the pressure in the test chamber during the propellant ignition process; both the oscilloscope (45) and the acquisition card (50) are triggered once by the rising edge of the voltage signal of the first high-voltage probe (28) to achieve time synchronization of the temperature signal (49), the pressure signal (48), the current signal (40), the trigger electrode voltage signal (46), and the anode voltage signal (47); the temperature signal (49) and the pressure signal (48) are used to represent the ignition moment and the plasma ignition efficiency; since a large amount of high-temperature and high-pressure gas is released during propellant ignition, the internal pressure of the test chamber (44) will increase significantly, and the ignition delay is defined as the time delay t from the moment t0 when the oscilloscope (45) and the acquisition card (50) are triggered by the first voltage pulse signal of the trigger electrode 3 collected by the first high-voltage probe (28) to the moment when the pressure signal (48) collected by the pressure sensor (34) in the test chamber (44) starts to rise to 10% of the maximum pressure fd ; t fd = t 10％ - t0 (6) The improvement effect of the plasma jet on the ignition efficiency of the propellant is characterized by the pressure rise rate, and the pressure rise rate r is defined p as the pressure change ΔP = P 90％ - P 10％ when the pressure rises from 10% to 90% of the maximum value during ignition, divided by the time Δt = t 90％ - t 10％ ; 10. The working method according to claim 7, characterized in that: A pulsed plasma jet generation system using an energetic doping working fluid can repeatedly generate plasma jets at a set frequency. Its working process is as follows: In each cycle, the control system (18) controls the DC power supply U2 in the LC series resonance charging circuit (17) to start charging by sending a charging start signal (23) to the full-hardware drive controller (24) in the LC series resonance charging circuit (17). The control system (18) inputs a turn-on signal (20) to the thyristor trigger circuit (16) at the set frequency to trigger a single capillary discharge to draw out a plasma jet. Each cycle of generating a plasma jet is divided into two steps: energy storage system charging and pulsed discharge to generate a plasma jet: 1) Energy storage system charging process: The control system (18) sends a charging start signal (23) to the full-hardware drive controller (24) in the LC series resonance charging circuit (17), and the LC series resonance charging circuit (17) starts to work. The full-hardware drive controller (24) inputs complementary PWM drive signals with a duty cycle of 25% to one group consisting of the first IGBT module S1 and the third IGBT module S3, and another group consisting of the second IGBT module S2 and the fourth IGBT module S4 to control the bridge arms to turn on alternately. The DC power provided by the DC power supply U2 is converted into AC power, stepped up by the transformer T, and then converted back into DC power through a diode full-bridge rectifier circuit to charge the energy storage capacitor to a high voltage of up to 2000V. The resistor voltage divider (26) connected to the output terminal collects the voltage of the energy storage capacitor C1, divides the 0 - 2000V capacitor voltage into a voltage signal of 0 - 1.5V, and inputs it into the full-hardware drive controller (24) through the opto-isolation module (25). It is compared with the set charging voltage through an operational amplifier circuit, and the gate circuit group judges whether the voltage of the energy storage capacitor C1 reaches the preset voltage. When the voltage of the energy storage capacitor C1 reaches the set charging voltage, the full-hardware drive controller stops inputting drive PWM signals to the first IGBT module S1, the second IGBT module S2, the third IGBT module S3, and the fourth IGBT module S4, and controls the fifth IGBT module S5 to turn off the charging circuit; 2) Pulsed discharge to generate a plasma jet process: When it reaches the trigger discharge moment, the control system (18) transmits a trigger plasma jet signal to the thyristor trigger circuit (16). The thyristor trigger circuit (16) transmits a second trigger signal (22) to the thyristor SCR1 in the pulsed current generation circuit (10) to control its conduction, and applies the voltage of the energy storage capacitor C1 between the anode (2) and the front flange cover (5). During the discharge process, the front flange cover (5) serves as the cathode. After a delay, the thyristor trigger circuit (16) inputs a first trigger signal (21) to the thyristor SCR2 in the pulsed voltage generation circuit to control its conduction, and applies a trigger high-voltage pulse to the trigger electrode (3) to induce surface discharge in the trigger channel (15) between the end of the anode (2) and the end of the trigger electrode (3); The triggering channel (15) forms an arc along the surface discharge, and the highly conductive plasma formed by ablation of the capillary tube wall material of the triggering channel (15) moves towards the front flange cover plate (5) serving as the cathode. When the plasma reaches the front flange cover plate (5) of the cathode, the capillary channel between the anode (2) and the front flange cover plate (5) of the cathode is filled with highly conductive plasma. The channel between the anode (2) and the front flange cover plate (5) of the cathode, that is, the high-voltage output terminal and the low-voltage output terminal of the pulsed current generation circuit (10) are short-circuited. A discharge loop is formed from the high-voltage output terminal of the pulsed current generation circuit (10) - the anode (2) - the arc in the capillary channel (12) - the front flange cover plate (5) of the cathode - the low-voltage output terminal of the pulsed current generation circuit (10). The electrical energy stored in the energy storage capacitor in the pulsed current generation circuit (10) starts to be released through the arc load in the capillary channel (12). The high-temperature arc radiation energy ablates the energy-doped working medium material in the capillary tube wall of the solid working medium to form a high-temperature and high-pressure plasma. The active metal powder and the polymer powder components in the plasma undergo a chemical reaction to release energy, further increasing the internal energy of the plasma jet; the inner wall material of the capillary channel (12) of the energy-doped working medium block (1) continuously undergoes phase change and decomposition and enters the interior of the capillary channel (12), increasing the internal pressure of the cavity, causing the plasma to continuously move towards the cathode nozzle (6) under the action of the pressure gradient, and finally ejecting outwards to generate a high-temperature and high-density plasma jet (13); The repetitive pulsed plasma jet generation system using the energy-doped working medium triggers and conducts the capillary channel (12) between the anode (2) and the front flange cover plate (5) through plasma jet. The ablation mass of the working medium block and the electrode during a single discharge is in the range of several milligrams to dozens of milligrams, and there is no obvious change in its morphology after a single discharge. Immediately after the energy storage of the pulsed current generation circuit (10) is completed, the next discharge starts.

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