Double electrode structure direct current plasma jet ignition device using solid working substance

Abstract

The application discloses a double-electrode structure direct-current plasma jet ignition device using solid working substance and belongs to the field of space ignition. The device comprises a trigger electrode, a cathode support, an insulator, a limiting screw, a cathode cover plate, a discharge channel, a PTFE polymer working substance block, a high-voltage trigger arc ignition circuit and a power arc maintaining circuit. The PTFE polymer working substance block is sleeved on the front end of the trigger electrode, the discharge channel is coaxially compressed with the trigger electrode and the cathode nozzle and is axially sealed in the cathode support. During operation, the high-voltage trigger arc ignition circuit generates a pulse to break through the discharge channel, the power arc maintaining circuit directly outputs a constant current to maintain the arc, and the inner wall of the working substance is ablated to generate a high-temperature plasma jet. The application uses the solid working substance to physically lock the discharge gap, avoids the increase of the breakdown threshold caused by electrode ablation, discards the traditional large energy storage capacitor, has the advantages of compact structure, light weight, long service life and continuous and stable jet, and is suitable for reliable ignition of non-solid propellants.

Description

Technical Field

[0001] This invention relates to the field of ignition technology for aerospace propulsion systems, mainly focusing on the ignition of non-solid propellants, and specifically to a DC plasma jet ignition device with a two-electrode structure 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 as a solution due to their compact structure, lack of need for additional tanks, and rapid response. Miniaturized ignition sources are used 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 by these thrusters 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 combines miniaturization, long life, and high reliability, can adapt to various non-solid propellants, and supports reusable operation, in order to meet the urgent need of next-generation aerospace propulsion systems for reliable ignition in extreme environments.

[0003] Although reusable two-gap discharge plasma devices already exist, such as the patent "Repetitive-Frequency Plasma Jet Ignition System and Method Using Energetic Modified Working Fluid, Patent No. ZL 2024 1 0430883.3", 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-frequency 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] To address the problems of existing ignition devices and specifically for volume- and weight-sensitive non-solid propellant aerospace propulsion systems, this invention aims to provide a DC plasma jet ignition device with a dual-electrode structure using a solid working medium. PTFE polymer is used as the solid working medium, and during discharge, the arc ablates the tube wall material components, allowing them to enter the plasma. This shortens the gap between the trigger electrode and the cathode plate, reducing the trigger voltage of the high-voltage triggering arc-ignition circuit. Simultaneously, the power arc-maintaining circuit directly and rapidly converts the electrical energy from the DC power supply system into the thermal energy needed to sustain the arc discharge and ablate the working medium to generate the plasma jet, eliminating reliance on traditional large-capacity pulse capacitors for charging and discharging, thus 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 DC plasma jet ignition device with a solid working fluid and a dual-electrode structure is used for ignition in aerospace propulsion systems. The device includes: A PTFE polymer working medium block 6 has a cylindrical discharge channel 9 pre-reserved at its axis; a trigger electrode 1 has a protruding cylindrical portion at its front end, the outer diameter of which is the same as the inner diameter of the discharge channel 9, and the PTFE polymer working medium block 6 is fitted onto the protruding cylindrical portion at the front end of the trigger electrode 1; a cathode cover plate 5 has a cylindrical nozzle at its center, the inner diameter of which is the same as the inner diameter of the discharge channel 9, and the discharge channel 9, the protruding cylindrical portion at the front end of the trigger electrode 1, and the cylindrical nozzle are strictly coaxially pressed together; a cathode support 3 is fixedly connected to the cathode cover plate 5; an insulator 4 encloses the trigger electrode 1 and the PTFE polymer working medium block 6 to achieve electrical insulation between the trigger electrode 1 and the cathode support 3; the trigger electrode 1, the insulator 4, and the PTFE... The PTFE polymer working medium block 6 is inserted into the cylinder of the cathode support 3, with its front end pressed against the inner wall of the cathode cover plate 5 and its rear end tightened by the limiting screw 2. The high-voltage trigger arc ignition circuit 10 has its high-voltage output terminal connected to the tail end of the trigger electrode 1, which is used to break down the discharge channel 9 to establish an initial arc channel. The power arc maintenance circuit 11 has its power output terminal connected to the tail end of the trigger electrode 1, which is used to output a constant current high power to maintain the arc after successful arc ignition, maintain stable arc combustion and ablate the PTFE polymer working medium block 6, and generate a high-temperature high-speed plasma jet 8. The cathode support 3 is grounded and connected to the grounding terminals of the high-voltage trigger arc ignition circuit 10 and the power arc maintenance circuit 11. The control module 12 sends a control signal 13 to start the power arc maintenance circuit 11 and sends a trigger control signal 14 to start the high-voltage trigger arc ignition circuit 10.

[0006] The high-voltage output terminal of the high-voltage triggering arc ignition circuit 10 is connected to the M4 threaded terminal at the tail end of the trigger electrode 1 via a high-voltage cable, generating a high-voltage pulse with an amplitude of 5~6kV and a pulse width of 2μs.

[0007] The power output terminal of the power arc-maintaining circuit 11 is connected in parallel with the high-voltage trigger terminal of the high-voltage trigger arc-starting circuit 10 to the tail of the trigger electrode 1, so as to provide a continuous low-impedance high current, maintain stable arc combustion and ablate the PTFE polymer working medium block 6.

[0008] The high-voltage triggering arc-starting circuit 10 includes: a high-voltage DC module U1, used to convert 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 14 sent by the control module 12 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.

[0009] The power arc-maintaining circuit 11 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 15 used to send a first PWM drive signal 16 with complementary duty cycles to the first switching transistor S1 and the third switching transistor S3, and a second PWM drive signal 17 with complementary duty cycles to the second switching transistor S2 and the fourth switching transistor S4; 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 diodes D5, D6, D7, and D8, 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 a 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.

[0010] Its working principle and process are as follows: The generation of thermal plasma through arc ablation of PTFE is essentially a cascade conversion of electrical energy into thermal, chemical, and kinetic energy, belonging to a typical ablation capillary discharge mechanism. A high-voltage triggering arc-ignition circuit applies a kV-level pulsed electric field between the trigger electrode and the cathode cover, causing Townsend avalanche breakdown of residual gas or PTFE surface-adsorbed gas within the discharge channel, forming an initial conductive channel. Subsequently, a high-power arc-maintaining circuit injects a large current (tens of amperes), and Joule heating instantly raises the channel temperature to over 5000K, completely ionizing the gas to form a high-temperature arc plasma. As a solid working fluid, the ablation of PTFE is not a simple melting and evaporation, but rather primarily involves 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 PTFE wall (accounting for 70%~90%), which is much higher than convection and conduction.

[0011] Depolymerization reaction: After absorbing radiation energy, the C-C bonds of PTFE molecular chains break, resulting in depolymerization, mainly producing tetrafluoroethylene monomers, difluorocarbenes, 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.

[0012] Boundary layer formation: Ablation products form a low-temperature, high-density vapor boundary layer (T≈3000~4000K) between the arc column and the PTFE wall. This layer protects the unablated PTFE bulk and also serves as a working fluid continuously injected into the arc core region. Ultimately, a C-based 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.

[0013] At the start of ignition, the high-voltage triggering arc-ignition circuit 10 emits a 5-6 kV high-voltage pulse, breaking down the discharge channel 9. The discharge channel 9 discharges on the inner surface of the PTFE polymer working medium block 6, forming an arc that ablates the PTFE polymer working medium block 6, creating high-conductivity plasma that moves towards the cathode cover plate 5. When the plasma reaches the cathode cover plate 5, the discharge channel 9 between the trigger electrode 1 and the cathode cover plate 5 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 11—the contact electrode 1—the high-temperature, high-speed plasma jet 8—the cathode cover plate 5—the cathode support 3—to grounding. The power arc-maintaining circuit 11 outputs a constant current with high power to maintain the arc. The high-temperature arc radiation energy ablates the energetic doped working medium material on the tube wall of the solid working medium, forming high-temperature, high-speed plasma. The material on the inner wall of the discharge channel 9 of the PTFE polymer working medium block 6 continuously undergoes phase change and decomposes, entering the interior of the discharge channel 9, increasing the internal pressure of the cavity. This causes the plasma to continuously move towards the nozzle of the cathode cover plate 5 under the action of the pressure gradient, and finally eject outwards to generate the high-temperature, high-speed plasma jet 8.

[0014] This invention abandons the traditional multi-electrode suspended discharge structure and adopts a two-electrode structure. The trigger electrode has a protruding cylindrical portion at its front end, and a PTFE polymer working fluid block is directly fitted onto this cylindrical portion. The inner diameter of the discharge channel (Φ3mm) is strictly consistent with the outer diameter of the trigger electrode and the inner diameter of the cathode cover nozzle, and the three are coaxially pressed together. Discharge no longer occurs across the air gap between the two metal electrodes, but rather on the inner wall of the PTFE solid working fluid block (discharge channel) between the trigger electrode and the cathode cover. As the number of discharge cycles accumulates, it is the inner wall of the PTFE working fluid block that is ablated and consumed, while the physical distance between the trigger electrode 1 and the cathode cover 5 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 fluid block and the distance is extremely short, the high-voltage triggering arc ignition circuit only needs to generate a low-voltage pulse of 5~6kV to reliably break down the channel, far lower than the 20kV of traditional devices, reducing 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 - insulator - PTFE working fluid block", which is inserted into the cathode support cylinder as a whole. The front end is pressed tightly against the inner wall of the cathode cover plate, and the rear end is axially pressed by screwing a limiting screw into the threaded hole at the tail of the support. This axial pressing design uses mechanical preload to directly ensure the airtightness of the discharge channel and prevent lateral plasma leakage. The elimination of complex flange seals or multiple O-ring designs greatly simplifies the shell structure, and the overall weight is strictly controlled to around 100g, achieving dual control over weight and volume. The system no longer relies on the "slow charging and fast discharging" of large-capacity capacitors, but instead uses the power supply directly through an LC resonant network to convert electrical energy into a constant current high power to maintain arc combustion in real time and continuously. This "on-demand" direct power drive 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, achieving a high degree of miniaturization and lightweighting of the system.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The igniter uses PTFE polymer material as the working fluid, which has a simple and reliable processing technology and is lightweight.

[0016] 2. Employing a dual-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.

[0017] 3. Rapid discharge is achieved without the need for large-volume energy storage capacitors, quickly outputting power from the supply to sustain the arc. The circuit utilizes integrated packaging, resulting in a high degree of miniaturization.

[0018] 4. It abandons the traditional metal wire arc ignition method and adopts gap breakdown arc ignition, enabling multiple repeated ignitions. Without changing the working fluid, it can achieve approximately 100 consecutive ignition cycles of 100ms each. The system is simple, reliable, and not prone to failure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall ignition device of the present invention.

[0020] Figure 2 This is a front view of the ignition device of the present invention.

[0021] Figure 3 This is a rear view of the ignition device of the present invention.

[0022] Figure 4 This is an axial cross-sectional view of the ignition device of the present invention.

[0023] Figure 5 This is a schematic diagram of a high-voltage trigger arc-starting circuit.

[0024] Figure 6 This is a schematic diagram of a power arc circuit.

[0025] Figure 7 This diagram shows the positional relationship between the discharge channel of the working fluid block and the trigger electrode and cathode plate.

[0026] Figure 8 A schematic diagram illustrating the coaxial nested structure of the trigger electrode, the outer insulator of the electrode, and the working fluid block to enhance the generation of thermal plasma jets by arc ablation of the working fluid surface.

[0027] Figure 9 This is a waveform diagram of the discharge circuit current.

[0028] Figure 10 The waveform of the capacitor voltage for jet ignition.

[0029] Figure 11 The diagram shows the energy and power of the discharge deposition in the ignition device.

[0030] Figure 12 The waveform diagram for triggering a high-voltage pulse. Detailed Implementation

[0031] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0032] like Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, the DC plasma jet ignition device with a solid working fluid dual-electrode structure includes a PTFE polymer working fluid block 6, which is made of PTFE granules and has a cylindrical discharge channel 9 at its center. The inner diameter of the center is the same as the outer diameter of the protruding cylindrical part 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 5. The three are coaxially pressed together. The cathode support 3 and the cathode cover plate 5 are tightened and fixed by M2 metal screws 7. The insulator 4 wraps around the trigger electrode 1 and the PTFE polymer working fluid block 6 to achieve electrical insulation between the trigger electrode 1 and the cathode support 3. The PTFE polymer working fluid block 6 is fitted onto the protruding cylindrical part at the front end of the trigger electrode 1. The three are inserted into the cylinder of the cathode support 3 as a whole, with the front end pressing against the inner wall of the cathode cover plate 5 and the rear end pressed by the limiting screw 2 to ensure that the high-temperature and high-speed plasma jet 8 in the discharge channel 9 can only be ejected along the cylindrical nozzle in the middle of the cathode cover plate 5.

[0033] The high-voltage output terminal of the high-voltage triggering arc ignition circuit 10 is connected to the tail end of the trigger electrode 1, and the power output terminal of the power arc stabilization circuit 11 is also connected to the tail end of the trigger electrode 1. The cathode support 3 is grounded and connected to the grounding terminals of the high-voltage triggering arc ignition circuit 10 and the power arc stabilization circuit 11.

[0034] Control module 12 sends control signal 13 to start power arc circuit 11, and control module 12 sends trigger control signal 14 to start high voltage trigger arc circuit 10.

[0035] The high-voltage output terminal of the high-voltage trigger arc ignition circuit 10 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 10 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 9 and establish the initial arc channel.

[0036] The power output terminal of the power arc-maintaining circuit 11 is also connected to the tail of the trigger electrode 1, and is connected in parallel with the high-voltage trigger arc circuit 10. After successful arc ignition, it provides a continuous low-impedance high current to maintain stable arc combustion and ablate the PTFE polymer working fluid block 6, generating a high-temperature, high-speed plasma jet 8.

[0037] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the discharge main assembly adopts a coaxial compression sealing structure, specifically including trigger electrode 1, limit screw 2, cathode support 3, insulator 4, cathode plate 5, PTFE polymer working fluid block 6, M2 metal screw 7, and high-temperature high-speed plasma jet 8.

[0038] PTFE polymer working block 6: Made of PTFE particles through molding and sintering process, it is cylindrical in shape. A cylindrical discharge channel 9 is pre-reserved in its center, with an inner diameter of Φ3mm (tolerance H7). The outer diameter of PTFE polymer working block 6 is Φ10mm, and its length is 15mm. It is fitted onto the protruding cylindrical part at the front end of the trigger electrode 1.

[0039] 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 9 of the PTFE polymer working medium block 6, 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.

[0040] Insulator 4: Made of alumina ceramic, it wraps around the middle section of trigger electrode 1 and the outer wall of PTFE polymer working block 6, achieving electrical insulation between trigger electrode 1 and cathode support 3. The outer diameter of insulator 4 is Φ14mm, which forms a clearance fit with the inner hole (Φ14mm, H8) of cathode support 3, making it easy to insert the whole into the cylinder of cathode support 3.

[0041] Cathode support 3 and cathode cover plate 5: The cathode support 3 is a stainless steel cylindrical structure, and its front end is tightened and fixed to the cathode cover plate 5 by eight evenly distributed M2 metal screws 7. The cathode cover plate 5 has a cylindrical nozzle at its center, with an inner diameter of Φ3mm (tolerance H7). The cathode cover plate 7 is 5mm thick and the nozzle is 3mm long, used to constrain and accelerate the ejection direction of the plasma jet 8.

[0042] Axial clamping and sealing: After the trigger electrode 1, insulator 4, and PTFE polymer working block 6 are inserted into the cathode support 3, the front end presses against the inner wall plane of the cathode cover plate 5, and the rear end is axially clamped by screwing the limiting screw 7 into the threaded hole at the tail of the cathode support 3. The preload torque of the limiting screw 7 is set to 2.5 N·m to ensure the airtightness of the discharge channel 9, prevent the high-temperature and high-speed plasma jet 8 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 5.

[0043] 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 PTFE discharge channel 9 (Φ3H7) is controlled between 0.01 and 0.015 mm, which ensures coaxiality and avoids the risk of seizure caused by the thermal expansion of PTFE.

[0044] The end face runout at the junction of the nozzle inner diameter (Φ3H7) of the cathode cover plate 5 and the discharge channel 9 is ≤0.02mm, which eliminates the step effect and reduces the energy loss of plasma flow.

[0045] The single-sided gap between the insulator 4 and the inner wall of the cathode support 3 is 0.02~0.05mm, which effectively suppresses surface flashover under high voltage while ensuring smooth assembly.

[0046] Through the above structural design, the ignition device achieves a compact layout. The PTFE polymer working block 6 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.

[0047] At the moment of ignition, the high-voltage arc-ignition triggering circuit 10 generates a 6KV high-voltage pulse, breaking down the discharge channel 9. The discharge channel 9 discharges along its surface, forming an arc that ablates the PTFE polymer working fluid block 6, creating a high-temperature, high-speed plasma jet 8 that moves towards the cathode cover plate 5. When the high-temperature, high-speed plasma jet 8 reaches the cathode cover plate 5, the discharge channel 9 between the trigger electrode 1 and the cathode cover plate 5 is filled with high-conductivity plasma. At this time, a current loop is formed between the power output terminal of the power arc-maintaining circuit 11, the contact electrode 1, the high-temperature, high-speed plasma jet 8, the cathode cover plate 5, the cathode support 3, and grounding. The power arc-maintaining circuit 11 outputs a constant current with high power to maintain the arc. The high-temperature arc radiation energy ablates the energetic doped working fluid material on the tube wall of the solid working fluid, forming a high-temperature, high-pressure plasma. The material on the inner wall of the discharge channel 9 of the PTFE polymer working fluid block 6 continuously undergoes phase change and decomposes, entering the interior of the discharge channel 9, increasing the internal pressure of the cavity. This causes the plasma to continuously move towards the cylindrical nozzle of the cathode cover plate 5 under the action of the pressure gradient, and finally eject outwards to generate the high-temperature, high-speed plasma jet 8.

[0048] like Figure 5 As shown, the high-voltage trigger arc ignition circuit 10 uses the high-voltage DC module U1 to convert the 28V DC power supply into 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 conducts after receiving the trigger control signal 14. The pulse is boosted to a 6KV output through transformer T1, as shown below. Figure 8 As shown.

[0049] like Figure 6As shown, the power arc-maintaining circuit 11 utilizes a full-bridge inverter topology. Through switches S1, S2, S3, and S4, it inverts the 100V DC power supply U2 into AC power. The AC voltage is then boosted by transformer T and rectified by diodes D5, D6, D7, and D8. Under the resonant effect of inductor L and capacitor C, a stable large current can be output to maintain the arc. The drive circuit 15 sends drive PWM signals 16 to switches S1 and S3, and drive PWM signals 17 to switches S2 and S4; signals 16 and 17 are PWM signals with complementary duty cycles.

[0050] Before the ignition system operates, a DC voltage source is simultaneously activated to charge the trigger capacitor C1 to approximately 1000V. Control module 12 sends control signal 13 to activate the power arc-maintaining circuit 11, charging the energy storage capacitor C to approximately 600V within 3 seconds. After a 3-second delay, control module 12 sends trigger control signal 14 to the high-voltage trigger arc-ignition switch S. The trigger capacitor C1 discharges to the primary side of the pulse transformer T1, generating a 5-6KV high-voltage pulse on the secondary side, breaking down the discharge channel 9. The discharge channel 9 discharges along its surface to form an arc. The discharge channel 9 ablates the PTFE polymer working fluid block 6, forming high-conductivity plasma that moves towards the cathode cover plate 5. When the high-conductivity plasma reaches the cathode cover plate 5, the discharge channel 9 between the trigger electrode 1 and the cathode cover plate 5 is filled with high-conductivity plasma. At this time, a current loop is formed between the power output terminal of the power arc-maintaining circuit 11—the contact electrode 1—the plasma jet 8—the cathode plate 5—the cathode support 3—and ground. The power arc-maintaining circuit 11 outputs a constant current high power to maintain the arc. High-temperature electric arc radiation can ablate the energetic doped working material on the tube wall of the PTFE polymer working block 6, forming a high-temperature and high-pressure plasma. The material on the inner wall of the discharge channel 9 of the PTFE polymer working block 6 undergoes continuous phase change and decomposition, entering the interior of the discharge channel 9 and increasing the internal pressure of the cavity. This causes the plasma to move continuously towards the nozzle of the cathode cover plate 5 under the action of the pressure gradient, and finally eject outward to generate a high-temperature and high-speed plasma jet 8.

[0051] Figure 7 The positional relationship between the discharge channel 9 of the working propellant block, the trigger electrode 1, and the cathode cover plate 5 is shown. Within the sealed cylindrical discharge channel (Φ3mm), the large amount of gas / plasma generated by PTFE ablation is confined to a small space and cannot expand freely. According to the law of conservation of mass and the equation of state, the pressure inside the channel rises sharply to the order of several MPa to tens of MPa. This high pressure is the fundamental source of the jet's kinetic energy. Simultaneously, the self-generated magnetic field produced by the axial current exerts a radial constriction effect on the plasma, further increasing the pressure and temperature in the axial region.

[0052] Figure 8The core innovation of this device lies in the coaxial nested structure of the trigger electrode 1, insulator 4, and PTFE polymer working fluid block 6. This structure not only achieves precise mechanical assembly but also significantly improves the efficiency and quality of generating a thermal plasma jet through three mechanisms: directional control of the thermal flow field, assurance of arc stability, and efficient energy conversion. This coaxial nested structure enhances the generation of a high-temperature, high-speed plasma jet 8 from the arc-ablated working fluid surface. Platform A, acting as a solid-plasma interface, generates a significant velocity gradient, forming a shear layer approximately 0.1 mm thick. The narrow space created by platform B further increases the plasma density and simultaneously generates high pressure within the cavity, squeezing and ejecting the plasma to form a plasma jet. This structure allows the ignition device to maintain high energy density, high repeatability, and high ignition reliability while achieving miniaturization.

[0053] Figure 9 The figure shows the discharge circuit current waveform of the present invention. It can be seen from the figure that the average arc current is about 12A during the normal discharge process of the igniter, and the current waveform is relatively stable.

[0054] Figure 10 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.

[0055] Figure 11 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.

[0056] Figure 12 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.

[0057] 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.

[0058] 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.

[0059] 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 DC plasma jet ignition device employing a dual-electrode structure with a solid working fluid, characterized in that, include: A PTFE polymer working block (6) with a cylindrical discharge channel (9) pre-reserved at its axis; a trigger electrode (1) with a protruding cylindrical part at its front end, the outer diameter of which is the same as the inner diameter of the discharge channel (9), the PTFE polymer working block (6) being fitted onto the protruding cylindrical part at the front end of the trigger electrode (1); a cathode cover plate (5) with a cylindrical nozzle at its center, the inner diameter of which is the same as the inner diameter of the discharge channel (9), the discharge channel (9), the protruding cylindrical part at the front end of the trigger electrode (1), and the cylindrical nozzle being tightly coaxially pressed together; a cathode support (3) fixedly connected to the cathode cover plate (5); an insulator (4) enclosing the trigger electrode (1) and the PTFE polymer working block (6) to achieve electrical insulation between the trigger electrode (1) and the cathode support (3); the trigger electrode (1), the insulator (4), and the PTFE The polymer working block (6) is inserted into the cylinder of the cathode support (3), with the front end pressing against the inner wall of the cathode cover plate (5) and the rear end pressed by the limiting screw (2); the high voltage trigger arc ignition circuit (10) has its high voltage output end connected to the tail end of the trigger electrode (1) and is used to break down the discharge channel (9) to establish the initial arc channel; the power arc maintenance circuit (11) has its power output end connected to the tail end of the trigger electrode (1) and is used to output constant current high power to maintain the arc after successful arc ignition, maintain stable arc combustion and ablate the PTFE polymer working block (6), and generate a high temperature and high speed plasma jet (8); the cathode support (3) is grounded and connected to the grounding end of the high voltage trigger arc ignition circuit (10) and the power arc maintenance circuit (11); the control module (12) sends a control signal (13) to start the power arc maintenance circuit (11), and the control module (12) sends a trigger control signal (14) to start the high voltage trigger arc ignition circuit (10).

2. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The PTFE polymer working block (6) is made of PTFE particles by molding and sintering process, and is cylindrical in shape. The inner diameter of the discharge channel (9) is Φ3mm, the outer diameter of the PTFE polymer working block (6) is Φ10mm, and the length is 15mm.

3. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The trigger electrode (1) is made of high-temperature resistant tungsten copper alloy material. The outer diameter of the protruding cylindrical part at the front end of the trigger electrode (1) is Φ3mm. The tail end of the trigger electrode (1) is provided with an M4 threaded terminal for connecting to an external circuit.

4. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The insulator (4) is made of alumina ceramic material and wraps around the middle section of the trigger electrode (1) and the outer wall of the PTFE polymer working block (6); the outer diameter of the insulator (4) is Φ14mm, which forms a clearance fit with the inner hole of the cathode support (3).

5. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The cathode support (3) is a stainless steel cylindrical structure, and its front end is tightened and fixed to the cathode cover plate (5) by multiple evenly distributed M2 metal screws (7); the cathode cover plate (5) has a thickness of 5mm, and the cylindrical nozzle has a length of 3mm.

6. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The limiting screw (2) is screwed into the threaded hole at the tail of the cathode support (3) for axial tightening. The pre-tightening torque is set to 2.5 N·m to ensure the airtightness of the discharge channel (9).

7. The uninterrupted plasma jet ignition device with a two-electrode structure using a solid working fluid as described in claim 1, characterized in that, The high-voltage output terminal of the high-voltage trigger arc-starting circuit (10) is connected to the M4 threaded terminal at the tail end of the trigger electrode (1) via a high-voltage cable, generating a high-voltage pulse with an amplitude of 5~6kV and a pulse width of 2μs.

8. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The power output terminal of the power arc-maintaining circuit (11) and the high-voltage trigger terminal of the high-voltage trigger arc-starting circuit (10) are connected in parallel to the tail of the trigger electrode (1) to provide a continuous low-impedance high current, maintain stable arc combustion and ablate the PTFE polymer working block (6).

9. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure as described in claim 1, characterized in that, The high-voltage triggering arc-starting circuit (10) 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 (14) sent by the control module (12) 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.

10. The DC plasma jet ignition device with a solid working fluid and a dual-electrode structure according to claim 1, characterized in that, The power arc-maintaining circuit (11) 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 (15), used to send a first PWM drive signal (16) with complementary duty cycles to the first switching transistor S1 and the third switching transistor S3, and a second PWM drive signal (17) with complementary duty cycles to the second switching transistor S2 and the fourth switching transistor S4; 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 diodes D5, D6, D7, and D8, 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 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.

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