Repetitively fired plasma jet ignition system and method employing a solid working medium

Abstract

This invention discloses a repetitive discharge plasma jet ignition system using a solid working medium and its operating method, belonging to the field of ignition technology for aerospace propulsion systems. The system includes a PTFE polymer working medium block, a trigger electrode, a cathode cover, a high-voltage trigger arc-ignition circuit, a power arc-maintaining circuit, a Hall current detection module, and a control module. Its operating method is as follows: the high-voltage trigger arc-ignition circuit generates a high-voltage pulse to break down the discharge channel and form an initial arc; the power arc-maintaining circuit uses DC-DC conversion and LC resonant topology to output a constant current high power to maintain the arc, ablating the PTFE polymer working medium to generate a high-temperature, high-speed plasma jet; the Hall current detection module monitors the loop current in real time to achieve automatic arc re-ignition after arc failure, ensuring uninterrupted discharge. This invention has advantages such as small size, light weight, reusability, high reliability, and adaptability to non-solid propellant ignition, effectively solving the problem of existing ignition devices struggling to balance miniaturization and long lifespan under extreme conditions.

Description

Technical Field

[0001] This invention relates to the field of ignition technology for aerospace propulsion systems, mainly focusing on the ignition of novel energetic propellants, specifically relating to a repetitive discharge plasma jet ignition system and method using a solid working fluid. Background Technology

[0002] Reliable ignition of aerospace propulsion systems under extreme conditions such as high altitude, high speed, low pressure, and low temperature is a critical prerequisite for the success or failure of spacecraft missions. However, traditional electric spark ignition methods are limited by low energy density, small ignition area, and poor adaptability to novel propellant molecular structures, facing severe reliability challenges under extreme conditions. Plasma ignition technology, with its unique thermo-chemical-aerodynamic coupling effect, significantly shortens ignition delay and widens the ignition boundary by generating high concentrations of active free radicals and volume excitation, becoming a research hotspot for solving these bottlenecks. Among them, solid working fluid pulsed plasma jets are particularly suitable for use due to their compact structure, lack of need for additional storage tanks, and rapid response. For miniaturized ignition sources to ignite non-solid propellants such as gaseous or liquid propellants; although there has been considerable accumulation in the field of pulsed plasma thrusters with solid working fluids both domestically and internationally, existing research has mostly focused on propulsion applications. There is still a lack of systematic solutions to the engineering challenges faced when using them as reusable ignition devices, such as short electrode ablation life, severe carbon deposition pollution, large single-impulse dispersion, and insufficient compatibility with different non-solid fuels. Therefore, there is an urgent need to develop an uninterrupted discharge plasma jet ignition device that takes into account miniaturization, long life, high reliability, adaptability to various propellants, and support for repeated operation, so as to meet the urgent need of next-generation aerospace propulsion systems for reliable ignition in extreme environments.

[0003] Although reusable discharge plasma devices with two gap structures already exist, such as the patent "Repetitive Frequency Plasma Jet Ignition System and Method Using Energetic Modified Working Fluid, Patent No. ZL 2024 10430883.3", they use high-cost and complex working fluid blocks, resulting in low cost-effectiveness in practical engineering applications. At the same time, the multi-electrode structure is complex, the requirements for the coordination between components are too high, and the maintenance and replacement are difficult. The energy deposition of repetitive pulse discharge is mostly reflected in the supersonic impact wave energy, which is difficult to generate sufficient electrothermal deposition on non-solid propellants. Summary of the Invention

[0004] Addressing the problems of existing ignition devices and targeting volume- and weight-sensitive non-solid propellant aerospace propulsion systems, this invention aims to provide a repetitive discharge plasma jet ignition system and method using a solid working fluid. PTFE polymer is used as the solid working fluid block, and during discharge, the arc ablates the tube wall material components, allowing them to enter the plasma. Shortening the gap between the trigger electrode and the cathode plate reduces the trigger voltage of the high-voltage arc-ignition circuit, preventing uncontrolled breakdown within the device during arc ignition and significantly reducing the power supply size. Furthermore, the power arc-maintaining circuit employs DC-DC conversion technology, utilizing an LC series resonant topology to directly and rapidly convert the electrical energy from the DC power supply system into the thermal energy necessary to sustain the arc discharge and ablate the PTFE polymer working fluid block, generating a high-temperature, high-speed plasma jet. This eliminates reliance on traditional large-capacity pulse capacitors for charging and discharging, ensuring the miniaturization and weight reduction of the ignition device.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: A repetitive discharge plasma jet ignition system using a solid working fluid, applicable to aerospace propulsion systems, comprises: a discharge main assembly, including a PTFE polymer working fluid block 9, a trigger electrode 1, a cathode cover plate 7, a cathode support 5, an insulator 2, and a support flange 4; the PTFE polymer working fluid block 9 has a cylindrical discharge channel 20 at its axial center; the front end of the trigger electrode 1, the discharge channel 20 of the PTFE polymer working fluid block 9, and a cylindrical nozzle in the middle of the cathode cover plate 7 are coaxially pressed together; the insulator 2 encloses the trigger electrode 1 and the PTFE polymer working fluid block 9 for electrical insulation; the support flange 4 is connected to the cathode support 5 and grounded; and a high-voltage trigger arc ignition circuit 12, whose high-voltage output terminal is connected to the tail end of the trigger electrode 1. The discharge channel 20 is broken down by a high-voltage pulse to form an initial arc; the power arc-maintaining circuit 13, whose power output terminal is connected to the tail of the trigger electrode 1, is used to output a constant current high power to maintain the arc combustion after successful arc ignition, and to ablate the PTFE polymer working fluid block 9 to generate a high-temperature high-speed plasma jet 17; the Hall current detection module 18 is connected in series in the grounding loop formed by the support flange 4 and the grounding terminals of the high-voltage trigger arc-ignition circuit 12 and the power arc-maintaining circuit 13, and is used to detect the arc current of the discharge loop in real time; the control module 11 is connected to the high-voltage trigger arc-ignition circuit 12, the power arc-maintaining circuit 13 and the Hall current detection module 18 respectively, and is used to send control signals and control the discharge and arc re-ignition of the system according to the current signal fed back by the Hall current detection module 18.

[0006] Preferably, the high-voltage triggering arc-starting circuit 12 includes: a high-voltage DC module U1, used to convert the input DC power into high-voltage DC power; and a current-limiting resistor R. c1 And trigger capacitor C1, the high voltage DC module U1 is connected through the current limiting resistor Rc1 The trigger capacitor C1 is charged; the high-voltage trigger arc ignition switch S receives the trigger control signal 16 sent by the control module 11 at its control terminal, and discharges the trigger capacitor C1 after being turned on; the pulse transformer T1 has its primary side connected to the high-voltage trigger arc ignition switch S and the trigger capacitor C1, and its secondary side is connected to the trigger electrode 1 as a high-voltage output terminal, which is used to boost the discharge pulse of the trigger capacitor C1 to a kilovolt-level high-voltage pulse output.

[0007] Preferably, the power arc-maintaining circuit 13 includes: a full-bridge inverter topology composed of four switching transistors S1, S2, S3, and S4, used to invert the DC power supply U2 into AC power; a drive circuit 21 used to send a first PWM drive signal 22 with complementary duty cycles to the first switching transistor S1 and the fourth switching transistor S4, and a second PWM drive signal 23 with complementary duty cycles to the second switching transistor S2 and the third switching transistor S3; a transformer T, whose primary side is connected to the full-bridge inverter topology, used to boost the AC voltage; a rectifier circuit composed of four diodes connected in series and then in parallel, connected to the secondary side of the transformer T, used to rectify the boosted AC power; and an LC resonant network composed of an inductor L and an energy storage capacitor C connected in series, connected to the output terminal of the rectifier circuit, used to output a stable large current under resonance to maintain the arc 24.

[0008] Preferably, the PTFE polymer working block 9 is formed by pressing PTFE particles.

[0009] The uninterrupted repetitive discharge method of the ignition system, based on the Hall current detection module 18 detecting the arc current to achieve uninterrupted discharge, includes the following steps: Step 1, Ignition system start-up and pre-charging: Control module 11 starts power arc circuit 13 to charge energy storage capacitor C to a predetermined threshold, and at the same time triggers capacitor C1 to pre-charge to high voltage state; Step 2, High-voltage triggering arc ignition: The control module 11 sends a trigger control signal 16 to make the high-voltage triggering arc ignition circuit 12 output a high-voltage pulse, which breaks down the discharge channel 20 to form an initial electric arc and ablates the PTFE polymer working block 9 to form a high-conductivity plasma through discharge channel 20. Step 3, Power Arc Maintenance and Jet Ejection: After the discharge channel 20 is turned on, the power arc maintenance circuit 13 outputs a constant current high power current to maintain the continuous combustion of the arc 24. The pressure inside the cavity increases, causing the high conductivity plasma to be ejected outward from the nozzle of the cathode cover plate 7 to form a high temperature and high speed plasma jet 17. Step 4, Current closed-loop monitoring and arc re-ignition: Hall current detection module 18 monitors the discharge current in the grounding loop in real time. If an arc interruption is detected within the preset working time t, causing the loop current to drop to 0, Hall current detection module 18 sends a re-trigger signal to control module 11. Control module 11 then re-executes steps 2 and 3, breaking down the discharge channel 20 again to form a high-temperature, high-speed plasma jet 17 until the preset working time t is reached. Step 5, work termination: After the preset working time t is reached, the control module 11 sends a control signal 15 to the power arc circuit 13 to forcibly shut down the output of the power arc circuit 13, interrupting the arc and terminating the high-temperature high-speed plasma jet 17.

[0010] In step 2, the high voltage pulse output by the high voltage triggering arc ignition circuit 12 has an amplitude of 5~6kV and a pulse width of microsecond-level narrow pulse.

[0011] In step 3, the power arc circuit 13 directly outputs a constant high-power current through the inverter-rectifier DC / DC conversion technology and the LC resonant network, without relying on a large-capacity pulse capacitor for energy storage and discharge.

[0012] The arc-reignition mechanism in step 4 is a closed-loop control. Within the effective working cycle of a single ignition signal, the Hall current detection module 18 and the control module 11 cooperate to perform multiple automatic re-triggering operations to ensure uninterrupted, continuous, and stable output of the plasma jet.

[0013] Its working principle and process are as follows: The generation of thermal plasma by arc ablation of the PTFE polymer working medium 9 is essentially a cascade conversion of electrical energy into thermal, chemical, and kinetic energy, belonging to a typical ablation capillary discharge mechanism. The high-voltage triggering arc-ignition circuit 12 applies a kV-level pulsed electric field between the trigger electrode 1 and the cathode cover plate 7, causing Townsend avalanche breakdown of the residual gas in the discharge channel 20 or the gas adsorbed on the surface of the PTFE polymer working medium 9, forming an initial conductive channel. Subsequently, the power arc-maintaining circuit 13 injects a large current (tens of amperes), and Joule heating causes the channel temperature to rise instantaneously to over 5000K, completely ionizing the gas to form a high-temperature arc plasma. As a solid working medium, the ablation of the PTFE polymer working medium 9 is not a simple melting and evaporation, but rather dominated by thermochemical decomposition. Radiation heat transfer is dominant: Ultraviolet / vacuum ultraviolet radiation generated in the high-temperature electric arc core region (>10,000K) is the main way of energy input to the wall of PTFE polymer working fluid block 9 (accounting for 70%~90%), which is much higher than convection and conduction.

[0014] Depolymerization reaction: After absorbing radiation energy, the C-C bonds of the PTFE polymer working fluid molecular chain break, resulting in depolymerization, mainly producing tetrafluoroethylene monomer, difluorocarbene, and a small amount of free radical fragments such as F. This process is a strongly endothermic reaction (ablation enthalpy of about 2~3 MJ / kg), effectively absorbing the energy of the electric arc and converting it into the internal energy and chemical potential energy of the working fluid.

[0015] Boundary layer formation: Ablation products form a low-temperature, high-density vapor boundary layer (T≈3000~4000K) between the arc column and the wall of the PTFE polymer working medium 9. This layer protects the unablated PTFE polymer working medium 9 body and also serves as a continuous injection of working medium into the arc core region. Ultimately, a C-type boundary layer is formed. + F + Electron and neutral fragment CF x The plasma is a mixed plasma dominated by fluorine particles. Due to the electronegativity and high emissivity of the fluorine particles, this plasma has high conductivity and a strong volumetric radiative cooling effect, which makes the arc voltage gradient relatively stable (usually on the order of 10~30 V / cm), which is beneficial to the stable power output of the arc circuit.

[0016] Before the ignition system operates, a DC voltage source is simultaneously activated to charge the discharge capacitor C1 to approximately 1000V. At ignition time, an ignition signal 14 needs to be sent from an external source to the control module 11. The control module 11 sends a control signal 15 to activate the power arc-maintaining circuit, charging the energy storage capacitor C to approximately 600V within 3 seconds. After a 3-second delay, the control module 11 sends a trigger control signal 16 to the high-voltage trigger arc-ignition switch S, causing capacitor C1 to discharge to the primary side of transformer T1 and generating a 5-6KV high-voltage pulse on the secondary side, breaking down the discharge channel 20. The discharge channel 20 discharges along its surface to form an electric arc, ablating the PTFE polymer working fluid block 9 in the discharge channel 20 to form high-conductivity plasma that moves towards the cathode cover plate 7. When the plasma reaches the cathode cover plate 7, the discharge channel 20 is filled with high-conductivity plasma. At this time, a current loop is formed from the power output terminal of the power arc-maintaining circuit 13 to the trigger electrode 1, the high-temperature high-speed plasma jet 17, the cathode cover plate 7, the cathode support 5, and grounding. The power arc-maintaining circuit 13 outputs a constant current and high power to maintain the electric arc 24. The high-temperature electric arc radiation energy ablates the energetic doped working fluid material on the tube wall of the solid working fluid to form high-temperature and high-pressure plasma. The material on the inner wall of the discharge channel 20 of the PTFE polymer working fluid block 9 undergoes continuous phase change and decomposition, entering the interior of the discharge channel 20, increasing the internal pressure of the cavity. This causes the plasma to continuously move towards the nozzle of the cathode cover plate 7 under the action of the pressure gradient, and finally eject outward to generate a high-temperature high-speed plasma jet 17.

[0017] Simultaneously, the Hall current detection module 18 measures the current in the discharge circuit. If the arc is interrupted during the duration of the ignition signal, the current in the grounding circuit drops to 0. The Hall current detection module 18 then sends the ignition signal 14 to the control module 11 again, which breaks down the discharge channel 20 again to form a high-temperature high-speed plasma jet 17 until the preset working time t is reached. Then, the control system 11 sends the control signal 15 to the power arc-maintaining circuit 13, interrupting the arc in the discharge channel 20 and terminating the high-temperature high-speed plasma jet 17.

[0018] This invention abandons the traditional multi-electrode suspended discharge structure and adopts a two-electrode structure. The trigger electrode 1 has a protruding cylindrical portion at its front end, and the PTFE polymer working medium block 9 is directly fitted onto this cylindrical portion. The inner diameter (Φ3mm) of the discharge channel 20 is strictly consistent with the outer diameter of the trigger electrode 1 and the inner diameter of the nozzle of the cathode cover plate 7, and the three are coaxially pressed together. The discharge no longer occurs across the air gap between the two metal electrodes, but rather on the inner wall (discharge channel) of the PTFE polymer working medium block 9 between the trigger electrode 1 and the cathode cover plate 7. With the accumulation of discharge cycles, it is the inner wall of the PTFE polymer working medium block 9 that is ablated and consumed, while the physical distance between the trigger electrode 1 and the cathode cover plate 7 is firmly locked by the external rigid structure and remains unchanged. Therefore, the breakdown threshold does not increase with the number of discharge cycles, completely breaking the vicious cycle of "ablation - widening gap - inability to break down". Because the gap is physically fixed by the solid working medium block and the distance is extremely short, the high-voltage triggering arc ignition circuit 12 only needs to generate a low-voltage pulse of 5~6kV to reliably break down the channel, which is far lower than the 20kV of traditional devices, thus reducing the dependence on the power supply output voltage from the source. The main body of the device adopts a three-layer coaxial nested structure of "trigger electrode 1 - insulator 2 - PTFE polymer working medium block 9", which is inserted into the cylinder of cathode support 5. The front end is pressed against the inner wall of cathode cover plate 7, and the rear end is axially pressed by screwing the limiting screw 3 into the threaded hole at the tail of the support. This axial pressing design uses mechanical pre-tightening force to directly ensure the airtightness of the discharge channel 20 and prevent lateral plasma leakage. There is no need for complex flange seals or multiple O-ring designs, which greatly simplifies the shell structure and strictly controls the overall weight to about 100g, achieving dual controllability of weight and volume. The system no longer relies on the "slow charging and fast discharging" of large-capacity capacitors, but uses the power supply to directly convert electrical energy into constant current high power to maintain arc combustion in real time and continuously through the LC resonant network. This "ready-to-use" direct-drive power mode completely eliminates the heavy and bulky energy storage capacitors and complex charging systems, keeping the total weight of the circuit module to around 1.5kg, thus achieving a high degree of miniaturization and lightweighting of the system.

[0019] Compared with the prior art, the present invention has the following advantages: 1. PTFE polymer working fluid is used as the igniter working fluid, which has a simple and reliable processing technology and a light working fluid weight.

[0020] 2. Employing a two-electrode structure design and relying on plasma jet triggering, the jet generator can achieve controllable, repeatable, and highly reliable discharge. No additional electrode structure is required, resulting in a lightweight and compact igniter weighing approximately 100g.

[0021] 3. Rapid discharge is achieved without the need for large-volume energy storage capacitors. A DC-DC circuit and LC resonator directly and rapidly output the power supply to sustain the arc. The circuit topology is reliable, and precise control ensures high robustness of the power supply system. The total weight of the high-voltage trigger arc-starting circuit 12, power arc-maintaining circuit 13, Hall current detection module 18, and control module 11 is approximately 1.5 kg, and they are integrated into a single package, resulting in a high degree of miniaturization of the overall system.

[0022] 4. It abandons the traditional metal wire arc ignition method and adopts gap breakdown arc ignition, enabling multiple repeated ignitions. Continuous ignition operation can be achieved without replacing the working fluid. The system is simple, reliable, and less prone to failure. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall ignition system of the present invention.

[0024] Figure 2 This is a front view structural diagram of the ignition system of the present invention.

[0025] Figure 3 This is a rear view structural diagram of the ignition system of the present invention.

[0026] Figure 4 This is an axial cross-sectional view of the ignition system of the present invention.

[0027] Figure 5 This is a schematic diagram showing the discharge channel of the PTFE polymer working medium and the positions of the trigger electrode and cathode cover.

[0028] Figure 6 This is a schematic diagram of a high-voltage trigger arc-starting circuit.

[0029] Figure 7 This is a schematic diagram of a power arc circuit.

[0030] Figure 8 This is a flowchart illustrating the process of achieving repeatable and uninterrupted discharge in an ignition system.

[0031] Figure 9 It is a coaxial nested structure of trigger electrode, external electrode insulator and working fluid block to enhance the thermal plasma jet pattern generated by arc ablation of the working fluid surface.

[0032] Figure 10 This is a waveform diagram of the discharge circuit current.

[0033] Figure 11 This is a waveform diagram of the voltage of the jet ignition capacitor.

[0034] Figure 12 This is a diagram showing the energy and power of the discharge deposition from the ignition device.

[0035] Figure 13 This is the waveform diagram of the triggered high-voltage pulse.

[0036] Figure 14 This is the result of a repeatable ignition test. Detailed Implementation

[0037] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0038] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, this invention employs a solid working fluid repetitive discharge plasma jet ignition system, including a PTFE polymer working fluid block 9, which is made of PTFE granules and has a cylindrical discharge channel 20 at its center. The inner diameter of the center is the same as the outer diameter of the protruding cylindrical portion at the front end of the trigger electrode 1 and the inner diameter of the cylindrical nozzle in the middle of the cathode cover plate 7, and the three are coaxially pressed together. The cathode support 5 and the cathode cover plate 7 are tightened and fixed by M2 metal screws 8. The insulator 2 encloses the trigger electrode 1 and the PTFE polymer working fluid block 9, achieving electrical insulation between the trigger electrode 1 and the cathode support 5. The PTFE polymer working fluid block 9 is fitted onto the protruding cylindrical portion at the front end of the trigger electrode 1. The three are inserted as a whole into the cylinder of the cathode support 5, with the front end pressing against the inner wall of the cathode cover plate 7 and the rear end pressed by the limiting screw 3, ensuring that the high-temperature, high-speed plasma jet 17 in the discharge channel 20 can only be ejected along the cylindrical nozzle in the middle of the cathode cover plate 7. The support flange 4 and the cathode support 5 are tightened together by M8 metal bolts, which facilitates the fixing of the igniter on the application device. The engine connector 6 in the figure is used to tighten the ignition device at the engine interface, while also forming heat insulation between the igniter and the outer wall of the engine.

[0039] The high-voltage output terminal of the high-voltage trigger arc-ignition circuit 12 is connected to the tail end of the trigger electrode 1, and the power output terminal of the power arc-maintaining circuit 13 is also connected to the tail end of the trigger electrode 1. The bracket flange 4 is grounded and connected to the grounding terminals of the high-voltage trigger arc-ignition circuit 12 and the power arc-maintaining circuit 13. The three circuits are connected in series and flow through the Hall current detection module 18. The control module 11 sends a trigger control signal 16 to the high-voltage trigger arc-ignition circuit 12 and a control signal 15 to the power arc-maintaining circuit 13.

[0040] The high-voltage output terminal of the high-voltage trigger arc ignition circuit 12 is connected to the M4 threaded terminal at the tail end of the trigger electrode 1 via a high-voltage cable. The high-voltage trigger arc ignition circuit 12 receives the trigger control signal 16 sent by the control module 11 and generates a high-voltage pulse with an amplitude of 6kV and a pulse width of 2μs, which is used to break down the gas medium in the discharge channel 20 and establish the initial arc channel.

[0041] The power output terminal of the power arc-maintaining circuit 13 is also connected to the tail of the trigger electrode 1, and is connected in parallel with the high-voltage trigger arc-ignition circuit 12. The power arc-maintaining circuit 13 receives the control signal 15 sent by the control module 11, and provides a continuous low-impedance high current after successful arc ignition to maintain stable arc combustion and ablate the PTFE polymer working fluid block 9, generating a high-temperature and high-speed plasma jet 17.

[0042] The bracket flange 4 is reliably grounded and connected to the grounding terminals of the high-voltage trigger arc ignition circuit 12 and the power arc maintenance circuit 13. The grounding wires of the three circuits are connected in series and then connected to the system ground after passing through the Hall current detection module 18. The Hall current detection module 18 collects the current waveform of the discharge circuit in real time to determine whether the arc ignition is successful, monitor the stability of the arc maintenance current, and realize the overcurrent protection function.

[0043] like Figure 5 As shown, the discharge channel 20 of the trigger electrode 1, the PTFE polymer working block 9, and the cylindrical nozzle in the middle of the cathode cover plate 7 are coaxially pressed together.

[0044] like Figure 6 As shown, the high-voltage trigger arc-starting circuit 12 includes: a high-voltage DC module U1, used to convert the input DC power into high-voltage DC power; and a current-limiting resistor R. c1 And trigger capacitor C1, the high voltage DC module U1 is connected through the current limiting resistor R c1 The trigger capacitor C1 is charged; the high-voltage trigger arc ignition switch S receives the trigger control signal 16 sent by the control module 11 at its control terminal, and discharges the trigger capacitor C1 after being turned on; the pulse transformer T1 has its primary side connected to the high-voltage trigger arc ignition switch S and the trigger capacitor C1, and its secondary side is connected to the trigger electrode 1 as a high-voltage output terminal, used to boost the discharge pulse of the trigger capacitor C1 to a kilovolt-level high-voltage pulse output. The high-voltage trigger arc ignition circuit 12 uses the high-voltage DC module U1 to convert the 28V DC power supply to 800V DC, and then uses the current-limiting resistor R to... c1 The trigger capacitor C1 is charged. The high-voltage trigger arc ignition switch S turns on after receiving the trigger control signal 16. The pulse is boosted to 6KV output through the pulse transformer T1.

[0045] like Figure 7As shown, the power arc-maintaining circuit 13 utilizes a full-bridge inverter topology, inverting the 100V DC power supply U2 into AC power through four switching transistors S1, S2, S3, and S4. After boosting the AC voltage through transformer T, it is rectified using diodes D5, D6, D7, and D8. Under the resonant effect of inductor L and energy storage capacitor C, a stable large current can be output to maintain the arc 24. The drive circuit 21 sends a first drive PWM signal 22 to the first switching transistor S1 and the fourth switching transistor S4, and a second drive PWM signal 23 to the second switching transistor S2 and the third switching transistor S3; wherein the first drive PWM signal 22 and the second drive PWM signal 23 are PWM signals with complementary duty cycles.

[0046] Before the ignition system operates, simultaneously turn on the DC voltage source to charge the trigger capacitor C1 to approximately 1000V. Figure 8 As shown, at the ignition moment, an ignition signal 14 needs to be sent from the outside to the control module 11. The control module 11 sends a control signal 15 to start the power arc-maintaining circuit 13, charging the energy storage capacitor C to about 600V within 3s; after a delay of 3s, the control module 11 sends a trigger control signal 16 to the high-voltage trigger arc-ignition switch S, triggering the capacitor C1 to discharge the primary side of the pulse transformer T1, and generating a 5-6KV high-voltage pulse on the secondary side, breaking down the discharge channel 20. The discharge channel 20 discharges along the surface to form an arc, ablating the PTFE polymer working fluid block 9 of the discharge channel 20 to form a high-conductivity plasma that moves towards the cathode cover plate 7. When the plasma reaches the cathode cover plate 7, the discharge channel 20 is filled with high-conductivity plasma. At this time, the power output terminal of the power arc-maintaining circuit 13—trigger electrode 1—high-temperature high-speed plasma jet 17—cathode cover plate 7—cathode support 5—grounding forms a current loop. The power arc-maintaining circuit 13 outputs a constant current high power to maintain the arc 24. High-temperature electric arc radiation can ablate the energetic doped working material on the tube wall of the solid working fluid, forming high-temperature and high-pressure plasma. The inner wall material of the discharge channel 20 of the PTFE polymer working fluid block 9 undergoes continuous phase change and decomposition, entering the interior of the discharge channel 20, increasing the internal pressure of the cavity. This causes the plasma to move continuously towards the nozzle of the cathode cover plate 7 under the action of the pressure gradient, and finally eject outward to generate a high-temperature and high-speed plasma jet 17.

[0047] Simultaneously, the Hall current detection module 18 measures the current in the discharge circuit. If the arc is interrupted during the duration of the ignition signal, the current in the grounding circuit drops to 0. The Hall current detection module 18 sends a repeat ignition signal 10 to the control module 11, which breaks down the power generation channel 20 again to form a high-temperature high-speed plasma jet 17 until the preset working time t is reached. At this time, the Hall current detection module 18 sends an end control signal 19 to the control module 11. The control system 11 then sends a control signal 15 to the power arc-maintaining circuit 13, interrupting the arc in the discharge channel 20 and terminating the high-temperature high-speed plasma jet 17.

[0048] Its complete working process is as follows: Step 1: Ignition system startup and pre-charge preparation After the ignition system is powered on, the control module 11 receives the "system start" signal; the control module 11 immediately outputs the control signal 15 to start the power arc circuit 13, so that the energy storage capacitor C begins to be charged by the DC voltage source at a constant current; this charging process lasts for 3 seconds (T=3s) until the voltage across the energy storage capacitor C reaches the predetermined threshold (about 600 V) and enters the saturated charging state; at the same time, before the system starts or during the synchronization phase, the trigger capacitor C1 has been pre-charged by the independent DC power supply to about 1000 V (this process can be completed in advance and does not occupy the main timing sequence).

[0049] Step 2: High-voltage triggering arc ignition After the energy storage capacitor C is fully charged, the control module 11 delays for 3 seconds (to ensure sufficient energy accumulation and system stability). Subsequently, the control module 11 outputs a trigger control signal 16 to drive the high-voltage trigger arc ignition switch S to turn on. The trigger capacitor C1 rapidly discharges through the high-voltage trigger arc ignition switch S to the primary side of the pulse transformer T1 (discharge time is about 20 μs, as shown in the flowchart with a narrow pulse width), inducing a high-voltage pulse with an amplitude of about 6 kV on the secondary side of the pulse transformer T1. This high-voltage pulse is applied to both ends of the discharge channel 20, breaking down the gas and medium in the channel to form a surface discharge channel 20, and initiating an initial arc on the surface of the PTFE polymer working block 9.

[0050] Step 3: Ablation gas generation and plasma cathode formation Under the initial high-temperature radiation of the electric arc and the Joule heating effect, the PTFE polymer working medium 9 undergoes pyrolysis, phase transformation and ablation along the inner wall of the discharge channel 20, releasing fluorinated carbon free radicals and small molecule gases; the ablation products are rapidly ionized to form high-conductivity plasma; this plasma extends towards the cathode cover plate 7; when the plasma front reaches the cathode cover plate 7, the discharge channel 20 is completely penetrated by the high-conductivity plasma, forming a low-impedance conductive path.

[0051] Step 4: Power-controlled arc and stable plasma jet injection Once the channel is turned on, the control module 11 detects the establishment of the loop current (see step 5), that is, the control signal 15 is kept valid, so that the power arc circuit 13 continuously outputs constant current high power; at this time, the current loop is: power output terminal of power arc circuit 13 — trigger electrode 1 — high temperature high speed plasma jet 17 — cathode cover plate 7 — cathode support 5 — ground; the constant high current maintains the stable combustion of the arc 24, continuously heats and further ablates the PTFE polymer working fluid block 9 of the tube wall; the pressure in the cavity increases due to the continuous ablation and gas production, and under the drive of the axial pressure gradient, the high temperature and high pressure plasma accelerates towards the nozzle of the cathode cover plate 7, and finally sprays outward in the form of high temperature high speed plasma jet 17.

[0052] Step 5: Current closed-loop monitoring and arc re-ignition protection The Hall current detection module 18 monitors the discharge circuit current in real time. If the arc is interrupted due to the depletion of working fluid, channel contamination, or disturbance within the preset working time t, the circuit current drops sharply to zero. After detecting that the current has returned to zero, the Hall current detection module 18 immediately sends a re-trigger request (repeated ignition signal 10) to the control module 11. After the control module 11 responds, it re-executes steps 2 to 4: that is, it sends the trigger control signal 16 again to trigger the high-voltage pulse, re-breaks down the discharge channel 20, and rebuilds the plasma path and jet. This closed-loop reignition mechanism can be repeated multiple times to ensure continuous and stable output of the plasma jet throughout the entire working cycle t.

[0053] Step 6: Work Termination and System Reset When the cumulative working time reaches the preset value t, the Hall current detection module 18 sends an end control signal 19 to the control module 11; the control module 11 issues a control signal 15 to forcibly shut down the output of the power arc-maintaining circuit 13; the energy storage capacitor C safely discharges through the discharge circuit, the arc 24 is extinguished, and the high-temperature high-speed plasma jet 17 is terminated; the system enters standby mode, waiting for the next ignition signal input, and prepares to enter a new working cycle.

[0054] like Figure 9 As shown, the discharge main assembly adopts a coaxial compression sealing structure, specifically including a trigger electrode 1, an insulator 2, a limit screw 3, a bracket flange 4, a cathode bracket 5, an engine connector 6, a cathode cover 7, an M2 metal screw 8, and a PTFE polymer working block 9.

[0055] PTFE polymer working block 9: Made of PTFE particles through molding and sintering process, it is cylindrical in shape with a pre-reserved cylindrical discharge channel 20 at its center. The inner diameter of the discharge channel 20 is Φ3mm (tolerance H7). The outer diameter of the PTFE polymer working block 9 is Φ10mm and the length is 15mm. It is fitted onto the protruding cylindrical part at the front end of the trigger electrode 1.

[0056] Trigger electrode 1: Made of high-temperature resistant tungsten-copper alloy. Its front end has a protruding cylindrical section with an outer diameter of Φ3mm (tolerance h6), which forms a transition fit with the inner diameter of the discharge channel 20 of the PTFE polymer working medium block 9, ensuring coaxiality and tight contact. The total length of trigger electrode 1 is 28mm, and its tail end has an M4 threaded terminal for connecting to external circuitry.

[0057] Insulator 2: Made of alumina ceramic, it encloses the middle section of trigger electrode 1 and the outer wall of PTFE polymer working block 9, achieving electrical insulation between trigger electrode 1 and cathode support 5. The outer diameter of insulator 2 is Φ14mm, which forms a clearance fit with the inner hole (Φ14mm, H8) of cathode support 5, making it easy to insert the whole into the cylinder of cathode support 5.

[0058] Cathode support 5 and cathode cover plate 7: The cathode support 5 is a stainless steel cylindrical structure, and its front end is tightened and fixed to the cathode cover plate 7 by four evenly distributed M2 metal screws 8. A cylindrical nozzle is located at the center of the cathode cover plate 7, with an inner diameter of Φ3mm (tolerance H7), which is consistent with the inner diameter of the discharge channel 20 and the outer diameter of the front end of the trigger electrode 1, and the three are strictly coaxial. The cathode cover plate 7 is 5mm thick, and the nozzle is 3mm long, used to constrain and accelerate the ejection direction of the high-temperature, high-speed plasma jet 17.

[0059] Axial clamping and sealing: After the trigger electrode 1, insulator 2, and PTFE polymer working block 9 are inserted into the cathode support 5, the front end presses against the inner wall plane of the cathode cover plate 7, and the rear end is axially clamped by screwing the limiting screw 3 into the threaded hole at the tail of the cathode support 5. The pre-tightening torque of the limiting screw 3 is set to 2.5 N·m to ensure the airtightness of the discharge channel 20, prevent the high-temperature and high-speed plasma jet 17 from leaking from the side, and ensure that it can only be ejected directionally along the cylindrical nozzle in the middle of the cathode cover plate 7.

[0060] Bracket flange 4: Bracket flange 4 is tightened to cathode bracket 5 with four M8 metal bolts. Flange 4 has four Φ6.5mm mounting holes for easy mounting of the entire igniter to the combustion chamber or test bench of the application device. Bracket flange 4 serves as the common grounding point for the entire device.

[0061] Engine connector 6: Engine connector 6 is used to tighten the ignition device to the engine interface, and at the same time form heat insulation between the igniter and the outer wall of the engine.

[0062] To ensure the miniaturization and reusability of the device, this embodiment strictly controls the key mating dimensions: The fitting gap between the cylindrical section (Φ3h6) at the front end of the trigger electrode 1 and the discharge channel 20 (Φ3H7) is controlled between 0 and 0.015 mm, which ensures coaxiality and avoids the risk of seizure caused by the thermal expansion of PTFE.

[0063] The end face runout at the junction of the nozzle inner diameter (Φ3H7) of the cathode cover plate 7 and the discharge channel 20 is ≤0.02mm, which eliminates the step effect and reduces the energy loss of plasma flow.

[0064] The single-sided gap between the insulator 2 and the inner wall of the cathode support 5 is 0.02~0.05mm, which effectively suppresses surface flashover under high voltage while ensuring smooth assembly.

[0065] Through the above structural design, the ignition device achieves a compact layout. The PTFE polymer working block 9 is the only consumable part that can be quickly replaced, while the remaining metal and ceramic parts can be reused, meeting the engineering application requirements of miniaturization, low cost and high reliability.

[0066] like Figure 10 The diagram shows the discharge circuit current waveform. It can be seen from the diagram that the average arc current during normal discharge of the igniter is approximately 12A, and the current waveform is relatively stable.

[0067] like Figure 11 The figure shows the voltage waveform of the jet ignition capacitor. It can be seen from the figure that the arc voltage changes drastically during the normal discharge of the igniter, exhibiting a violent fluctuation pattern.

[0068] like Figure 12 The graph shows the discharge deposition energy and power of the ignition device. The dynamic relationship between power and energy can be seen from the graph. The deposition energy of the ignition device in 550ms is approximately 450J.

[0069] like Figure 13 The figure shows the high-voltage pulse waveform at the output of the high-voltage triggering arc ignition circuit. It can be seen from the figure that the trigger voltage pulse width is about 0.2μs (half-width at half maximum) and the peak value reaches 6kV, which reflects the typical pulse triggering characteristics of fast rise time (<0.5μs) and narrow pulse width.

[0070] Figure 14 These are test photos of a repeatable ignition experiment that can achieve five consecutive ignitions. The continuous ignition experiment proves that the invention has the capability for repeated ignition, which can meet the requirements of multiple ignitions in aerospace propulsion systems.

[0071] This invention differs from traditional high-repetition-rate pulsed capillary plasma jet devices in terms of working fluid type, structural design, and application: Regarding the working medium, through parameter diagnosis of the pulsed discharge channel based on the energetic doped working medium, the results show that the discharge electrical parameters of the energetic doped working medium are close to those of polytetrafluoroethylene (PTFE), with a heat flux density only about 1.5% higher. Furthermore, it requires a large-mass pulse capacitor, making it difficult to miniaturize the device. In terms of fabrication process, the energetic doped working medium is complex to process, with high uncertainty in material doping, which has a certain impact on discharge stability. Therefore, this invention selects PTFE polymer as the working medium for generating thermal plasma.

[0072] Second, in terms of device structure, existing dual-gap jet generators typically have a relatively compact spacing between the trigger electrode and the anode, maintained within a range of only 2 to 3 millimeters. Consequently, the trigger driving voltage is also relatively limited, with the trigger peak generally controlled below 20 kV. As the number of discharge cycles accumulates, the electrode material undergoes geometric changes due to ablation and wear, causing the effective trigger gap to gradually widen. This leads to a continuous increase in the breakdown threshold. Once the gap expands to the point where the required breakdown potential exceeds the maximum output voltage that the power supply can provide, the discharge process will be interrupted, severely limiting the cumulative service life of the device. Furthermore, such devices are extremely complex in their electrode and outer casing design, making quality control difficult. The power supply mainly relies on large-capacity capacitors for energy storage, resulting in an excessively large overall device size. In contrast, the device of this invention greatly simplifies the ignition device. It employs a dual-electrode excitation method, where a high-voltage triggering arc-ignition circuit excites a 5-6 kV voltage to break down the gap, generating a discharge path. A power arc-maintaining circuit then sustains the arc, continuously ablating the inner wall of the working fluid block to generate plasma. Under high temperature and pressure, the hot plasma is ejected from the narrow aperture to form a plasma jet. Meanwhile, the device of this invention utilizes the power supply to directly output power through the power arc circuit, eliminating the heavy and bulky charging system and energy storage capacitor of the traditional pulse repetition frequency ignition system, thereby miniaturizing the ignition device and greatly reducing its weight.

[0073] Third, in terms of application background, existing reusable two-gap jet devices are used in fields such as long air gap conduction and high heat load simulation, and are only suitable for the ignition of solid propellants; while the DC pulse plasma jet device of this invention is applied to aerospace propulsion systems using non-solid propellants. The system is simple, reliable, and not prone to failure, and has strong prospects for application and promotion.

Claims

1. A repetitive discharge plasma jet ignition system using a solid working fluid, characterized in that, This ignition system is used for ignition in aerospace propulsion systems and includes: a discharge main assembly, which includes a PTFE polymer working block (9), a trigger electrode (1), a cathode cover plate (7), a cathode support (5), an insulator (2), and a support flange (4); the PTFE polymer working block (9) has a cylindrical discharge channel (20) at its axial center, and the front end of the trigger electrode (1), the discharge channel (20) of the PTFE polymer working block (9), and the cylindrical nozzle in the middle of the cathode cover plate (7) are coaxially pressed together; the insulator (2) wraps around the trigger electrode (1) and the PTFE polymer working block (9) to achieve electrical insulation; the support flange (4) is connected to the cathode support (5) and grounded; a high-voltage trigger arc ignition circuit (12) is used to generate a high-voltage pulse, the high-voltage output end of which is connected to the tail end of the trigger electrode (1). The discharge channel (20) is impacted to form an initial arc; the power arc-maintaining circuit (13), whose power output end is connected to the tail of the trigger electrode (1), is used to output constant current high power to maintain arc combustion after successful arc ignition, and to ablate the PTFE polymer working medium block (9) to generate a high-temperature high-speed plasma jet (17); the Hall current detection module (18) is connected in series in the grounding loop formed by the bracket flange (4) and the grounding end of the high-voltage trigger arc-ignition circuit (12) and the power arc-maintaining circuit (13), and is used to detect the arc current of the discharge loop in real time; the control module (11) is connected to the high-voltage trigger arc-ignition circuit (12), the power arc-maintaining circuit (13) and the Hall current detection module (18) respectively, and is used to send control signals and control the discharge and arc re-ignition of the system according to the current signal fed back by the Hall current detection module (18).

2. The ignition system according to claim 1, characterized in that, The high-voltage triggering arc-starting circuit (12) includes: a high-voltage DC module (U1) for converting input DC power into high-voltage DC power; and a current-limiting resistor (R). c1 The high-voltage DC module (U1) is connected to the current-limiting resistor (R) and the trigger capacitor (C1). c1 The trigger capacitor (C1) is charged; the high-voltage trigger arc ignition switch (S) receives the trigger control signal (16) sent by the control module (11) at its control terminal, and discharges the trigger capacitor (C1) after being turned on; the pulse transformer (T1) has its primary side connected to the high-voltage trigger arc ignition switch (S) and the trigger capacitor (C1), and its secondary side is connected to the trigger electrode (1) as a high-voltage output terminal, which is used to boost the discharge pulse of the trigger capacitor (C1) to a kilovolt-level high-voltage pulse output.

3. The ignition system as described in claim 1, characterized in that, The power arc-maintaining circuit (13) includes: a full-bridge inverter topology, consisting of four switching transistors S1, S2, S3 and S4, used to invert the DC power supply (U2) into AC power; a drive circuit (21), used to send a first PWM drive signal (22) with complementary duty cycles to the first switching transistor S1 and the fourth switching transistor S4 and a second PWM drive signal (23) with complementary duty cycles to the second switching transistor S2 and the third switching transistor S3; a transformer (T), whose primary side is connected to the full-bridge inverter topology, used to boost the AC voltage; a rectifier circuit, consisting of four diodes connected in series and then in parallel, connected to the secondary side of the transformer (T), used to rectify the boosted AC power; and an LC resonant network, consisting of an inductor (L) and a storage capacitor (C) connected in series, connected to the output end of the rectifier circuit, used to output a stable large current under resonance to maintain the arc (24).

4. The ignition system as described in claim 1, characterized in that, The PTFE polymer working block (9) is made by pressing PTFE particles.

5. A method for continuous repetitive discharge operation of an ignition system as described in any one of claims 1 to 4, characterized in that, The uninterrupted discharge is achieved by detecting the arc current using the Hall current detection module (18), including the following steps: Step 1, Ignition system start-up and pre-charging: The control module (11) starts the power arc circuit (13) to charge the energy storage capacitor (C) to a predetermined threshold, and at the same time triggers the capacitor (C1) to pre-charge to a high voltage state; Step 2, high voltage triggering arc ignition: The control module (11) sends a trigger control signal (16) to make the high voltage triggering arc ignition circuit (12) output a high voltage pulse, break down the discharge channel (20) to form an initial electric arc, and ablate the PTFE polymer working block (9) to form a high conductivity plasma through discharge channel (20). Step 3, Power Arc Maintenance and Jet Ejection: After the discharge channel (20) is turned on, the power arc maintenance circuit (13) outputs a constant current high power current to maintain the arc (24) to continue burning. The pressure inside the cavity increases, causing high conductivity plasma to be ejected outward from the nozzle of the cathode cover plate (7) to form a high temperature and high speed plasma jet (17). Step 4, Current closed-loop monitoring and arc re-ignition: The Hall current detection module (18) monitors the discharge current in the grounding loop in real time. If the arc interruption is detected within the preset working time t, causing the loop current to drop to 0, the Hall current detection module (18) sends a re-trigger signal to the control module (11). The control module (11) re-executes steps 2 and 3, and breaks down the discharge channel (20) again to form a high-temperature high-speed plasma jet (17) until the preset working time t is reached. Step 5, work termination: After the preset working time t is reached, the control module (11) sends a control signal (15) to the power arc circuit (13) to forcibly shut down the output of the power arc circuit (13), the electric arc is interrupted, and the high-temperature high-speed plasma jet (17) is terminated.

6. The uninterrupted repetitive discharge method according to claim 5, characterized in that, In step 2, the high voltage pulse output by the high voltage triggering arc ignition circuit (12) has an amplitude of 5~6kV and a pulse width of microsecond-level narrow pulse.

7. The uninterrupted repetitive discharge method according to claim 5, characterized in that, In step 3, the power arc circuit (13) directly outputs a constant high-power current through the DC / DC conversion technology of inverter-rectifier and LC resonant network, without relying on a large-capacity pulse capacitor for energy storage and discharge.

8. The method for continuous repetitive discharge according to claim 5, characterized in that, The arc-reignition mechanism in step 4 is a closed-loop control. Within the effective working cycle of a single ignition signal, the Hall current detection module (18) and the control module (11) work together to perform multiple automatic re-triggering operations to ensure uninterrupted and stable output of the plasma jet.

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