Plasma jet ignition device and method using energetic doping and modified working fluid

Abstract

A plasma jet ignition device and method using an energetically doped and modified working fluid. The plasma jet ignition device comprises an energetically doped working fluid block, an anode, a trigger electrode, an insulator, a housing, a cathode nozzle, a rear cover, a limit screw, a pulse voltage generating circuit, and a pulse current generating circuit. The ignition device uses a modified polymer doped with an active metal element as a capillary working fluid. During capillary discharge, the metal element and the polymer enter the plasma, where they undergo a chemical reaction, releasing chemical energy to increase jet energy, thereby raising the temperature and internal energy of the plasma jet and improving ignition efficiency. A three-electrode, two-gaps structural design allows for capillary discharge by conducting an arc between the anode and cathode using the plasma jet triggering principle, thereby achieving repeatable operation of the jet ignition device. By increasing the trigger voltage and strengthening the insulation design between the trigger electrode and the housing, the device improves adaptability to shortened electrode ablation lengths, thereby increasing the number of continuous operations of the jet device.

Description

Technical Field

[0001] The present invention relates to the technical field of ignition of aerospace propulsion systems, and in particular to a plasma jet ignition device and method using an energetically doped and modified working fluid. Background Art

[0002] Ignition of aerospace propulsion systems transitions the system from inoperative mode to operational mode, and reliability is a prerequisite for its application. Advances in aerospace technology have made engine re-ignition difficult under extreme flight conditions, such as high altitude, high speed, low pressure, and low temperature. Traditional spark ignition methods offer low ignition energy, a small ignition zone, and poor ignition reliability under these extreme conditions. New propellants have a different molecular structure than traditional fuels, and traditional ignition methods also face reliability challenges. Therefore, developing a highly reliable ignition system is crucial, and plasma ignition technology is a research hotspot.

[0003] Plasma ignition uses gas discharge to create a localized high-temperature region, stimulating a large number of active particles and rapidly initiating combustion of the fuel. Plasma ignition relies primarily on thermal, aerodynamic, and chemical effects of active particles. Compared to traditional ignition methods, plasma ignition boasts a large ignition area, short ignition delay, and high ignition energy utilization. Depending on the discharge form, it can be categorized as direct breakdown arc ignition, sliding arc discharge, nanosecond pulsed corona discharge ignition, and plasma jet ignition.

[0004] The capillary discharge plasma jet has high temperature (>10000K), high speed (1-10km / s), high heat flux density (up to GW / m 2 Due to its characteristics of high pressure (ranging from several MPa to tens of MPa), capillary discharge has applications in a variety of fields, including space electrothermal propulsion, material surface modification, propellant ignition, hazardous material disposal, and triggering long air trigger gaps. Compared to other plasma ignition methods, capillary discharge uses only solid working fluids and does not rely on complex gas and piping systems. Its simple and reliable structure reduces system failure rates, allows for a larger ignition area, and enables non-contact ignition.

[0005] However, the capillary discharge jet has a short existence time, generally only tens of microseconds to milliseconds. In open space and large-volume combustion chambers, it cannot provide long-term confinement for high-temperature and high-pressure plasma. In addition, the ignition of the aerospace propulsion system requires the ignition system to be able to operate repeatedly. Traditional capillary discharge mostly relies on the electric explosion of metal wire to conduct the capillary channel. After each discharge, the metal detonating wire needs to be replaced, and it cannot be operated repeatedly. Summary of the Invention

[0006] In response to the problems existing in the capillary plasma jet device in the prior art, the purpose of the present invention is to provide a plasma jet ignition device and method using an energetically doped modified working fluid. An energetically doped polymer is used as the capillary working fluid block, aiming to cause the arc to ablate the tube wall material components into the plasma during discharge, so that the active metal components and the polymer components therein undergo a chemical reaction to release energy, thereby increasing the jet temperature and heat flow, and improving the ignition efficiency.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A plasma jet ignition device using an energetically doped modified working medium comprises a housing 8, an energetically doped working medium block 1 coaxially mounted within the housing 8, the energetically doped working medium block 1 being made of active metal powder ranging from nanometer to micrometer size, mixed with polymer powder, pressed, sintered, and machined to form a modified energetic working medium, and a capillary channel 12 being machined at the axis, and a cylindrical channel 14 being machined on the side to communicate with the capillary channel 12; the front portion of the housing 8 being connected to a front flange cover plate 5, and the rear portion being connected to a rear flange cover plate 7; an expanded cathode nozzle 6 being coaxially machined on the front flange cover plate 5; an anode 2 being inserted into the capillary channel 12 from the rear portion of the energetically doped working medium block 1, and a trigger electrode 3 being inserted from the energetically doped working medium block 1 to the capillary channel 12; A cylindrical channel 14 is inserted into the side of the miscellaneous medium block 1, dividing the capillary channel 12 between the end of the anode 2 and the front flange cover 5 into two parts: a part between the anode 2 and the trigger electrode, called the trigger channel 15, and a part between the trigger electrode 3 and the front flange cover 5; insulators 4 are installed outside the anode 2 and the trigger electrode 3 to achieve electrical isolation from the outer casing; in terms of connection with the external circuit, the high voltage output end of the pulse voltage generating circuit 9 is connected to the trigger electrode 3, the low voltage output end of the pulse voltage generating circuit 9 is connected to the front flange cover 5, the high voltage output end of the pulse current generating circuit 10 is connected to the anode 2, and the low voltage output end of the pulse current generating circuit 10 is connected to the front flange cover 5.

[0009] The no-load output voltage of the pulse voltage generating circuit 9 is 39 kV. When the breakdown voltage required to trigger the gap 15 is higher than the output voltage of the pulse voltage generating circuit 9, the plasma jet ignition device cannot be triggered to cause capillary discharge plasma jet and cannot work.

[0010] The energetic doping working medium block 1 and the insulator 4 are interlocked with each other to increase the surface distance, increase the outer surface distance of the insulator 4, and prevent flashover discharge from occurring at positions other than the trigger gap 15, resulting in trigger failure.

[0011] The interlocking structure is that the insulator 4 is first gradually expanded and then has a constant diameter in the energetically doped working medium block 1 .

[0012] The cathode nozzle 6 has a conical expansion shape with a cone angle of 5°-15°.

[0013] A limit screw 11 is installed on the outside of the insulator 4 and fixedly connected to the housing 8.

[0014] The preparation method of the energetic doping working medium block 1 is as follows:

[0015] Active metal powders of nanometer to micron size are mixed with polymer powders of micron particle size in a certain proportion, with the active metal powder accounting for 3%-26% of the total mass of the powders, or some active metal oxide powders are doped to improve the mechanical properties of the energetic working medium block, or a small amount of ammonium perchlorate powder is added to increase the chemical energy released by the reaction; all the powders are placed in a blender for shear mixing and then placed in a cylindrical hydraulic press mold with a hole in the middle, the filling is completed at one time, the pressure is applied and maintained, and then the pressure of the hydraulic press is gradually released to form a cylindrical mold with a through hole in the middle. The column blank is left to stand to eliminate internal stress and then sintered in an argon protective atmosphere. First, the temperature is raised to 370-390 degrees Celsius at a heating rate of 50 degrees Celsius per hour, kept warm for 2-6 hours, then cooled to 327 degrees Celsius at a cooling rate of 50 degrees Celsius per minute, kept warm for 2 hours, and then cooled to room temperature at a cooling rate of 50 degrees Celsius per minute; finally, through mechanical processing, the axial position of the working fluid block is processed into a capillary channel 12, and a cylindrical channel 14 is processed vertically inward on the side of the cylindrical working fluid block to connect with the capillary channel 12.

[0016] The active metal powder is aluminum powder or boron powder; the polymer powder is polytetrafluoroethylene, high-density polyethylene or polyetheretherketone.

[0017] The operating method of the plasma jet ignition device using an energetically doped and modified working medium is as follows: turning on the solid-state switch in the pulse current generating circuit 10 applies a 1-2 kV high voltage between the anode 2 and the front flange cover 5. During the discharge process, the front flange cover 5 acts as a cathode; after a delay, the pulse voltage generating circuit 9 applies a trigger high voltage pulse to the trigger electrode 3, inducing creeping discharge in the trigger channel 15 between the ends of the anode 2 and the trigger electrode 3;

[0018] The trigger channel 15 discharges along the surface to form an arc, and the high-conductivity plasma formed by the arc ablating the capillary wall material of the trigger channel 15 moves toward the front flange cover plate 5 serving as the cathode. When the plasma reaches the cathode front flange cover plate 5, the capillary channel between the anode 2 and the cathode front flange cover plate 5 is filled with high-conductivity plasma, and the channel between the anode 2 and the cathode front flange cover plate 5, that is, the high-voltage output end and the low-voltage output end of the pulse current generating circuit 10 are short-circuited, and the discharge loop from the high-voltage output end of the pulse current generating circuit 10 - the anode 2 - the arc in the capillary channel 12 - the cathode front flange cover plate 5 - the low-voltage output end of the pulse current generating circuit 10 is formed. The electric energy stored in the energy storage capacitor in the pulse current generating circuit 10 begins to be released through the arc load in the capillary channel 12. The high-temperature arc radiation energy causes the capillary wall of the solid working fluid to ablate the energetically doped working fluid material to form a high-temperature and high-pressure plasma. The active metal powder and the polymer powder components in the plasma undergo a chemical reaction to release energy, further increasing the internal energy of the plasma jet. The inner wall material of the capillary channel 12 of the energetically doped working fluid block 1 continuously undergoes phase change and decomposes into the interior of the capillary channel 12, increasing the internal pressure of the cavity, so that the plasma continuously moves toward the cathode nozzle 6 under the action of the pressure gradient, and is finally ejected outward to generate a high-temperature and high-density plasma jet 13.

[0019] The plasma jet ignition device triggers the capillary channel 12 between the anode 2 and the cathode front flange cover 5 through plasma jetting. The mass of the working fluid block and the electrode ablation in a single discharge is between several milligrams and tens of milligrams. There is no obvious change in the morphology after a single discharge. The next discharge can be started immediately after the pulse current generating circuit 10 completes energy storage.

[0020] Although there are already reusable two-gap capillary discharge plasma devices, such as the patent "A combination wave circuit for driving ablation capillary discharge, patent number CN201610256978.3" and the paper "Experimental study on transient high heat load generation based on capillary discharge plasma", the present invention differs from these reusable two-gap capillary jet devices in terms of working fluid type, structural design, and application scenarios:

[0021] (1) In terms of working fluid type, existing reusable capillary discharge jet devices use ordinary polymer working fluids, such as polyethylene and polytetrafluoroethylene. During the ablation process, a large amount of arc energy needs to be absorbed for the dissociation, gasification, and ionization of chemical bonds in the polymer compound to generate plasma. However, the present invention uses a modified polytetrafluoroethylene working fluid doped with aluminum and boron of nanometer to micrometer particle size. During the ablation process, the high temperature causes the components to undergo chemical reactions and release chemical energy, which can compensate for part of the energy loss during the ablation process and increase the jet energy. The reaction equation is:

[0022] 4Al+3C2F4=4AlF3+6C+Q1

[0023] Where Q1 is the heat released by the reaction, and the energy released can reach 14.9 kJ / g.

[0024] (2) In terms of device structure, the gap between the trigger electrode and the anode of the existing reusable two-gap jet device is relatively short, generally only 2-3 mm, and the trigger electrode voltage is not high, generally not exceeding 20 kV. When the electrode is ablated and shortened during multiple discharges, the trigger gap increases and the breakdown voltage gradually increases. When the trigger gap length increases to the point where the required trigger voltage is higher than the peak value of the trigger electrode input voltage, the device cannot be broken down, which limits the number of uses. In addition, the insulation between the electrode and the shell is not reinforced. The device of the present invention takes into account the factor that the trigger electrode becomes longer due to electrode ablation, and increases the no-load voltage applied to the trigger electrode to 39 kV. The interlocking contact surface structure is used to strengthen the inner and outer surface lengths of the trigger electrode insulator to prevent surface flashover between the device and the shell. The high trigger voltage can achieve breakdown with a longer trigger gap, which is well adapted to the process of shortening the trigger gap due to electrode ablation and lengthening, and can achieve more repeated discharges.

[0025] (3) In terms of application background, the existing repeatable two-gap jet device is used in the fields of long air gap conduction, high heat load simulation, etc., while the capillary plasma jet device of the present invention is used in the field of aerospace propulsion system ignition.

[0026] The preparation method of energetically doped polymer working fluid is mentioned in the paper “Theoretical and Experimental Study on the Working Process of Pulsed Plasma Thruster and Working Fluid Modification”, but the working fluid block structure, working environment and doping purpose in the paper are essentially different from those of the present invention.

[0027] The modified working fluid block in the paper is applied to the pulsed plasma thruster. The structure of the working fluid block is a rectangular parallelepiped. It works in a vacuum environment. The conductivity of the ablation plasma is changed by doping, and then the current flowing through the plasma is changed. The purpose is to change the thrust parameters of the thruster. The energetic doped working fluid block of the present invention is applied to the capillary plasma jet igniter. It is made into a coaxial structure with a capillary through hole. During the discharge process, the pressure in the working fluid block capillary can reach several MPa. The purpose of doping is to increase the jet energy through heat release by chemical reaction.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. Using energetic polymer materials as igniter working fluids to increase plasma jet temperature and heat flux, utilizing electrothermal acceleration mechanisms to accelerate energetic particles, and bombarding the propellant surface to enhance local hot spots can improve ignition efficiency.

[0030] 2. The three-electrode structure design relies on plasma jet triggering to achieve controllable, repeatable and highly reliable discharge of the jet ignition device; increasing the trigger electrode voltage and enhancing the insulator surface length to adapt to the shortened electrode ablation length and increased trigger gap breakdown voltage, thereby achieving more discharge times.

[0031] 3. The energy-boosting heavy-frequency plasma jet is produced by using a fully solid working medium, which does not require an ignition material storage and supply device or mechanism. The system is simple, reliable, and not prone to failure.

[0032] 4. The output voltage of the pulse voltage generating circuit is increased to adapt to the lengthening of the trigger gap for multiple discharges, thereby achieving more discharge times. At the same time, a mutually interlocking connection structure is used between the insulator and the energetic doping working medium block to increase the surface distance, and the length of the outer surface of the insulator 4 is increased to enhance the electrical insulation strength of the jet device, so as to avoid the problem of insulation damage in other positions caused by the increase in the output voltage of the pulse voltage generating circuit 9. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a structural principle diagram of the plasma jet ignition device using an energetic doping and modified working medium according to the present invention.

[0034] Figure 2 Schematic diagram of the position of the capillary channel and the side cylindrical channel of the energetic doping working fluid block.

[0035] Figure 3 The following is a typical discharge voltage and current waveform of a pulsed thermal plasma jet ignition device using an aluminum-based energetic working fluid.

[0036] Figure 4 Schematic diagram of the interlocking structure of the trigger electrode, insulator at the anode and working medium block to enhance the surface length and surface insulation.

[0037] Figure 5 (a) to (b) are schematic diagrams of the change in the trigger gap lengthening caused by multiple discharge ablation electrode shortening.

[0038] Figure 6 This is the sintering temperature curve of the energy-enhancing working fluid.

[0039] Figure 7 The flowchart of the preparation of the energized capillary discharge working fluid block is shown. DETAILED DESCRIPTION

[0040] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0041] The present invention provides a plasma jet ignition device using an energetic doping modified working medium, comprising an energetic doping working medium block 1, such as Figure 2As shown, the energetic doping block 1 is made of aluminum powder or boron powder of micron to nanometer scale, mixed with polymer powder such as polytetrafluoroethylene, high-density polyethylene or polyetheretherketone, pressed, sintered, and machined into a cylindrical capillary channel 12 with a central axis and a cylindrical channel 14 on the side to communicate with the capillary channel 12. Figure 1 As shown, the energetic doping working medium block 1 is coaxially installed inside the housing 8; the front of the housing 8 is connected to the front flange cover plate 5, and the rear is connected to the rear flange cover plate 7; the front flange cover plate 5 is coaxially processed with an expanded cathode nozzle 6; the anode 2 is inserted into the capillary channel 12 from the rear of the energetic doping working medium block 1, and the trigger electrode 3 is inserted from the cylindrical channel 14 on the side of the energetic doping working medium block 1, dividing the capillary channel 12 between the end of the anode 2 and the front flange cover plate 5 into a portion between the anode 2 and the trigger electrode, called the trigger channel 15, and the trigger electrode The two parts are between the pole 3 and the front flange cover 5; the insulator 4 is installed outside the anode 2 and the trigger electrode 3 to achieve electrical isolation from the shell, and the limit screw 11 is installed on the outside of the insulator 4 and fixedly connected to the shell 8; in terms of connection with the external circuit, the high voltage output end of the pulse voltage generating circuit 9 is connected to the trigger electrode 3, the low voltage output end of the pulse voltage generating circuit 9 is connected to the front flange cover 5, the high voltage output end of the pulse current generating circuit 10 is connected to the anode 2, and the low voltage output end of the pulse current generating circuit 10 is connected to the front flange cover 5.

[0042] The preparation method of the energetic doped working medium block 1, taking doped aluminum powder as an example, is as follows: Figure 7 As shown:

[0043] Aluminum powder of nanometer to micron size is mixed with polytetrafluoroethylene powder of micron particle size in a certain proportion, with aluminum powder accounting for 3%-26% of the total mass of the powder. Some alumina powder can be doped to improve the mechanical properties of the energetic working medium block, or a small amount of ammonium perchlorate (AP) powder can be added to increase the chemical energy released by the reaction. After all the powders are sheared and mixed evenly in a blender, they are placed in a cylindrical hydraulic press mold with a hole in the middle. The filling is completed at one time and maintained at a pressure of 20 MPa for 5 minutes. After that, the hydraulic press pressure is gradually released to form a cylindrical blank with a through hole in the middle. The blank is left to stand for 24 hours to eliminate internal stress and then sintered in a tubular furnace with an argon protective atmosphere. The temperature curve is set as follows: Figure 6As shown: First, the temperature is raised to 380°C at a rate of 50°C per hour, held at this temperature for 6 hours, then cooled to 327°C at a rate of 50°C per minute, held for 2 hours, and finally cooled to room temperature at a rate of 50°C per minute. This ensures both complete melting and uniform mixing of the polytetrafluoroethylene powder and the crystallinity of the sample after cooling, thus ensuring sufficient mechanical strength. Finally, a capillary channel 12 with a diameter of 1-10 mm and a length of 10-100 mm is machined into the axial center of the working block to accommodate the anode 2. A cylindrical channel 14 with a diameter of 1-5 mm and a depth equal to the cylinder radius is machined perpendicularly inwardly into the side of the cylindrical working block. The distance from the machined channel to the bottom of the cylindrical working block is 25 mm, allowing for the insertion of the trigger electrode 3 in the center.

[0044] exist Figure 1 The characteristics and connection methods of the components inside the plasma jet ignition device are as follows:

[0045] Energetic doping working fluid 1, energetic materials include but are not limited to aluminum-based, boron-based micron, nano-scale energetic metal powders blended with polymer powders such as polytetrafluoroethylene, high-density polyethylene, polyetheretherketone, etc., injection molded, pressed, and formed. This type of working fluid can further release chemical energy during discharge, and the plasma jet has the characteristics of high temperature, high pressure, high heat flux, etc., and is suitable for ignition applications; the energetic doping working fluid 1 usually adopts a hollow cylindrical configuration, the diameter of the hollow structure is usually 1 to 10 mm, and the length of the cylinder is usually 10-100 mm.

[0046] The cathode nozzle 6 is an integrated structure with the front flange cover 5. It is used to position and secure the front of the energetic doping block 1 and also serves as the cathode in the discharge circuit. The diameter of the through-hole of the cathode nozzle 6 near the front flange cover 5 matches the diameter of the capillary channel 12 in the energetic doping block 1. The cathode nozzle 6 adopts a conical expansion shape with a cone angle of 5°-15° to increase the plasma jet velocity while better constraining its expansion, thereby concentrating the plasma jet energy. The front flange cover 5 is connected to the housing 8 via a bolt-flange structure.

[0047] Housing 8 is a coaxial stainless steel structure with a thickness of 4mm to provide sufficient mechanical strength. Its internal diameter is the same as that of the energetic-doped working fluid block 1, ensuring a tight fit. It is also the same length as the energetic-doped working fluid block 1. A threaded hole is machined in the center, at the same location as the through-hole for inserting the energetic-doped working fluid block into the trigger electrode, for mounting the trigger electrode and insulator on the side. Flanges are machined on both sides for bolted connection to the front and rear flange covers 5 and 7.

[0048] The trigger electrode 3 is made of brass or copper-tungsten alloy and is arranged on the shell 8. The end of the electrode extends into the interior of the energetically doped working fluid block 1. Its length allows its end face to contact the wall of the central capillary channel 12 of the energetically doped working fluid block 1. It is insulated from the shell 8 by the insulator 4.

[0049] The insulator 4 is made of insulating materials such as nylon, polyetheretherketone, alumina ceramics, etc., and is fixed to the housing 8 by a limit screw 11 made of stainless steel. Its bottom is connected to the energetic doping working medium block 1 through a mutual interlocking structure, such as Figure 4 As shown in the figure, the internal surface insulation path from the high potential electrode to the low potential limit screw and the shell part is a broken line ABCD. Through the bite structure design, the surface distance is maximized in the limited space inside the working fluid block, and its flashover voltage is increased to prevent the occurrence of insulation failure and unexpected discharge, which leads to the failure of triggering the capillary discharge plasma jet. Figure 4 As shown, the external surface insulation path is EFG, and external flashover discharge is prevented by increasing the height of the insulator 4.

[0050] By strengthening the insulation design of the insulator 4 structure, the compactness of the device can be improved, the volume and weight can be reduced, and the voltage that the trigger electrode can withstand can be increased without causing unexpected discharge. After multiple discharges, the anode 2 and the trigger electrode 3 are burned by the arc, and their lengths are continuously shortened. The length of the trigger gap 15 between the end of the anode 2 and the end of the trigger electrode 3 gradually increases, and the required breakdown voltage gradually increases. Figure 5 As shown, Figure 5 In (a), HI is the trigger gap in the initial state. Figure 5 In (b), KJ is the trigger gap after multiple discharges. Figure 1 The high pulse voltage design in the Chinese and foreign circuit pulse voltage generation circuit 9 can output a no-load trigger voltage amplitude of up to 39kV, enabling breakdown of trigger gaps less than 13mm without causing insulation failure. This is well adapted to extending the trigger gap for electrode ablation, enabling more discharges and extending the life of the fluidic device.

[0051] The rear flange cover 7 is designed with a flange structure identical to that of the housing and is connected to the housing 8 via a bolt-flange structure. A threaded hole is machined at its axis to match the limit screw 11.

[0052] The anode 2 is inserted into the tail of the capillary channel 12 of the energetically doped working medium block 1 . It has the same structure and material as the trigger electrode 3 and is also insulated from the rear flange cover 7 by the insulator 4 . The insulator 4 , the anode 2 and the rear flange cover 7 are fixed by the limit screws 11 .

[0053] The end of the anode 2, the end of the trigger electrode 3 and the cavity surface of the energetic doping working medium block 1 form a trigger gap 15.

[0054] The trigger electrode 3 and the front flange cover 5 are connected to the pulse voltage generating circuit 9 through a wire. The trigger electrode 3 is connected to the high level output of the pulse voltage generating circuit, and the front flange cover 5 is connected to the ground terminal of the pulse voltage generating circuit.

[0055] The pulse voltage generating circuit 9 outputs a pulse voltage with a no-load amplitude of 39 kV and a pulse width of 500 ns.

[0056] The anode 2 and the front flange cover 5 are connected to the high-level terminal and the ground terminal of the pulse current generating circuit 10 via wires. The pulse current generating circuit 10 uses a high-energy-density metallized film capacitor for energy storage, which is controlled on and off by a thyristor solid-state switch. The typical charging voltage is 2kV, and the energy storage capacitor has an adjustable capacitance of 140μF to 560μF, storing 280J-1120J of energy. By pulse discharge in the capillary channel 12, an arc is formed, ablating the capillary wall material to form a high-temperature, high-pressure plasma, which is ejected from the cathode nozzle 6 to form a high-temperature, high-density plasma jet 13.

[0057] The energized plasma jet ignition device provided by this invention uses an energetically doped working fluid, has an overall mass of less than 2 kg, and features a simple and reliable structure. Relying solely on a pure solid-state working fluid, it eliminates the need for complex gas path valves and other devices, special vacuum environments, and explosion-proof measures. It can generate high-temperature, high-pressure, and high-heat-flux plasma under atmospheric conditions. This reduces the likelihood of failure in complex environments and is suitable for ignition in aerospace propulsion systems, where reliability is critical. Its operating principle is as follows:

[0058] like Figure 1 As shown, the solid-state switch in the pulse current generating circuit 10 is turned on, and a high voltage of 1-2 kV is applied between the anode 2 and the front flange cover 5. During the discharge process, the front flange cover 5 acts as a cathode. After a delay of 5 μs, the pulse voltage generating circuit 9 applies a trigger high-voltage pulse to the trigger electrode 3, inducing surface discharge in the channel 15 between the end of the anode 2 and the end of the trigger electrode 3.

[0059] The trigger channel 15 discharges along the surface to form an arc, and the high-conductivity plasma formed by the arc ablation of the capillary wall material of the trigger channel 15 moves toward the front flange cover plate 5 serving as the cathode. When the plasma reaches the cathode front flange cover plate 5, the capillary channel between the anode 2 and the front flange cover plate 5 (cathode) is filled with high-conductivity plasma, and the channel between the anode 2 and the cathode front flange cover plate 5, that is, the high voltage output terminal and the low voltage output terminal of the pulse current generating circuit 10 are short-circuited, and the high voltage output terminal of the pulse current generating circuit 10 - the anode 2 is short-circuited. —The arc in the capillary channel 12—the cathode front flange cover 5 (cathode)—the discharge loop at the low voltage output end of the pulse current generating circuit 10 is formed. The electric energy stored in the energy storage capacitor in the pulse current generating circuit 10 begins to be released through the arc load in the capillary channel 12. The high-temperature arc radiation energy causes the capillary tube wall of the solid working fluid to ablate the energetically doped working fluid material to form a high-temperature and high-pressure plasma. The active components such as aluminum powder in the plasma chemically react with the polytetrafluoroethylene (PTFE) component to release energy, further increasing the internal energy of the plasma jet. The inner wall material of the capillary channel 12 of the energetically doped working fluid block 1 continuously changes phase and decomposes into the interior of the capillary channel 12, increasing the internal pressure of the cavity, so that the plasma continuously moves toward the cathode nozzle 6 under the action of the pressure gradient, and finally ejects outward to produce a high-temperature and high-density plasma jet 13; when the capacitor charging voltage is 2000V and the energy storage is 280J, the single discharge voltage and current waveforms are as follows: Figure 3 As shown, the discharge current peak is about 7.4 kA, the plasma jet triggering process delay is about 74 μs from the breakdown of the trigger gap 15, and the entire discharge process is about 130 μs.

[0060] It should be noted that after multiple discharges, the length of the anode 2 and the trigger electrode 3 continues to shorten due to arc erosion, and the length of the trigger gap 15 between the end of the anode 2 and the end of the trigger electrode 3 gradually increases, and the required breakdown voltage gradually increases. If the required breakdown voltage of the trigger gap 15 is higher than the output voltage of the pulse voltage generating circuit 9, the plasma jet ignition device will not be able to trigger the capillary discharge plasma jet and will not work. This device increases the no-load voltage output by the pulse voltage generating circuit 9 to 39kV, and increases the surface distance by designing a structure that interlocks between the energetic doping working fluid block 1 and the insulator 4, thereby increasing the outer surface distance of the insulator 4, thereby preventing flashover discharge from occurring at locations other than the trigger gap 15, resulting in trigger failure.

[0061] The capillary discharge plasma jet device triggers the capillary channel 12 between the anode 2 and the cathode front flange cover 5 through plasma injection. The mass of the working fluid block and the electrode ablation in a single discharge is between several milligrams and tens of milligrams. There is no obvious change in its morphology after a single discharge. The next discharge can be started immediately after the pulse current generating circuit 10 completes energy storage.

[0062] The present invention proposes a plasma jet ignition device using a Hanergy doped and modified working fluid. Based on the principle of pulsed plasma jets generated by capillary discharge of an all-solid working fluid, it proposes the use of an energized modified polymer working fluid doped with active metal powders such as aluminum powder or boron powder. The chemical reaction between the components of the ablated energetic doped working fluid releases energy, further increasing the jet temperature and energy, thereby improving ignition efficiency. The energized, repetitive plasma jet ignition device uses an all-solid working fluid and does not require an ignition material storage and supply device or mechanism, resulting in a simple, reliable system that is less prone to failure. The design increases the trigger electrode voltage and the length of the insulator along the surface, shortening the electrode ablation length to increase the breakdown voltage of the trigger gap, achieving more discharges and extending the life of the jet device. The three-electrode structure, triggered by plasma jets, enables controllable, repeatable, and highly reliable discharge of the jet generating device, improving the operating performance of the plasma jet ignition device.

Claims

1. A plasma jet ignition device using an energetic doping and modifying working medium, characterized in that: The invention comprises a shell (8), an energetic doping medium block (1) coaxially mounted inside the shell (8), the energetic doping medium block (1) being made of active metal powder ranging from nanometer to micrometer level, mixed with polymer powder, pressed, sintered and machined to form a modified energetic medium, and a capillary channel (12) being machined on the axis, and a cylindrical channel (14) being machined on the side to communicate with the capillary channel (12); the front of the shell (8) being connected to the front flange cover plate (5), and the rear being connected to the rear flange cover plate (7); an expanded cathode nozzle (6) being coaxially machined on the front flange cover plate (5); an anode (2) being inserted into the capillary channel (12) from the rear of the energetic doping medium block (1), and a trigger electrode (3) being inserted into the capillary channel (12) from the cylindrical channel (14) on the side of the energetic doping medium block (1). 14) is inserted to separate the capillary channel (12) between the end of the anode (2) and the front flange cover (5) into two parts: a part between the anode (2) and the trigger electrode, called the trigger channel (15), and a part between the trigger electrode (3) and the front flange cover (5); an insulator (4) is installed outside the anode (2) and the trigger electrode (3) to achieve electrical isolation from the shell; in terms of connection with the external circuit, the high voltage output end of the pulse voltage generating circuit (9) is connected to the trigger electrode (3), the low voltage output end of the pulse voltage generating circuit (9) is connected to the front flange cover (5), the high voltage output end of the pulse current generating circuit (10) is connected to the anode (2), and the low voltage output end of the pulse current generating circuit (10) is connected to the front flange cover (5); The no-load output voltage of the pulse voltage generating circuit (9) is 39 kV, so as to prevent the required breakdown voltage of the trigger channel (15) from being higher than the output voltage of the pulse voltage generating circuit (9), thereby preventing the plasma jet ignition device from being unable to trigger the capillary discharge plasma jet and thus being unable to work; The energetic doping working medium block (1) and the insulator (4) are interlocked with each other to increase the surface distance, thereby increasing the outer surface distance of the insulator (4) and preventing flashover discharge from occurring at locations other than the trigger channel (15) and causing trigger failure.

2. The plasma jet ignition device using an energetic doping and modifying working medium according to claim 1, characterized in that: The mutually interlocking structure is a structure in which the insulator (4) first gradually expands and then has a constant diameter within the energetically doped working medium block (1).

3. The plasma jet ignition device using an energetic doping and modifying working medium according to claim 1, characterized in that: The cathode nozzle 6 has a conical expansion shape with a cone angle of 5°-15°.

4. The plasma jet ignition device using an energetic doping and modifying working medium according to claim 1, characterized in that: A limiting screw (11) is used to install it on the outside of the insulator (4) and is fixedly connected to the housing (8).

5. The plasma jet ignition device using an energetic doping and modifying working medium according to claim 1, characterized in that: The preparation method of the energetic doping working medium block (1) is as follows: Active metal powders with nanometer to micron size are mixed with polymer powders with micron particle size in a certain proportion, with the active metal powder accounting for 3%-26% of the total mass of the powders, or some active metal oxide powders are doped to improve the mechanical properties of the energetic working medium block, or a small amount of ammonium perchlorate powder is added to increase the chemical energy released by the reaction; all the powders are placed in a blender for shear mixing, and then placed in a cylindrical hydraulic press mold with a hole in the middle, the filling is completed at one time, and pressure is applied and maintained, and then the pressure of the hydraulic press is gradually released to form a cylindrical wool with a through hole in the middle. The blank is left to stand to eliminate internal stress and then sintered in an argon protective atmosphere. First, the temperature is increased to 370-390 degrees Celsius at a heating rate of 50 degrees Celsius per hour, kept at this temperature for 2-6 hours, then cooled to 327 degrees Celsius at a cooling rate of 50 degrees Celsius per minute, kept at this temperature for 2 hours, and then cooled to room temperature at a cooling rate of 50 degrees Celsius per minute. Finally, the axial position of the working fluid block is machined into a capillary channel (12) by mechanical processing, and a cylindrical channel (14) is vertically machined inward on the side of the cylindrical working fluid block to communicate with the capillary channel (12).

6. The plasma jet ignition device using an energetic doping and modifying working medium according to claim 5, characterized in that: The active metal powder is aluminum powder or boron powder; the polymer powder is polytetrafluoroethylene, high-density polyethylene or polyetheretherketone.

7. The operating method of a plasma jet ignition device using an energetically doped and modified working medium according to any one of claims 1 to 6, characterized in that: A solid-state switch in the pulse current generating circuit (10) is turned on to apply a high voltage of 1-2 kV between the anode (2) and the front flange cover (5), with the front flange cover (5) serving as a cathode during the discharge process; after a time delay, the pulse voltage generating circuit (9) applies a trigger high-voltage pulse to the trigger electrode (3), inducing creeping discharge in the trigger channel (15) between the end of the anode (2) and the end of the trigger electrode (3); The trigger channel (15) discharges along the surface to form an arc, and the high-conductivity plasma formed by the arc ablating the capillary wall material of the trigger channel (15) moves toward the front flange cover (5) serving as the cathode. When the plasma reaches the cathode front flange cover (5), the capillary channel between the anode (2) and the cathode front flange cover (5) is filled with high-conductivity plasma, and the channel between the anode (2) and the cathode front flange cover (5), that is, the high voltage output end and the low voltage output end of the pulse current generating circuit (10) are short-circuited, and the high voltage output end of the pulse current generating circuit (10) - the anode (2) - the arc in the capillary channel (12) - the cathode front flange cover (5) - the low voltage output end of the pulse current generating circuit (10) is short-circuited. A discharge loop is formed at the output end, and the electric energy stored in the energy storage capacitor in the pulse current generating circuit (10) begins to be released through the arc load in the capillary channel (12). The high-temperature arc radiation energy causes the capillary tube wall of the solid working medium to ablate the energetically doped working medium material to form a high-temperature and high-pressure plasma, and the active metal powder and polymer powder components in the plasma undergo a chemical reaction to release energy, further increasing the internal energy of the plasma jet; the inner wall material of the capillary channel (12) of the energetically doped working medium block (1) continuously undergoes phase change and decomposes into the interior of the capillary channel (12), increasing the internal pressure of the cavity, so that the plasma continuously moves toward the cathode nozzle (6) under the action of the pressure gradient, and is finally ejected outward to generate a high-temperature and high-density plasma jet (13); The plasma jet ignition device triggers the capillary channel (12) between the anode (2) and the cathode front flange cover (5) through plasma jetting. The mass of the working fluid block and the electrode ablation in a single discharge ranges from several milligrams to tens of milligrams. After a single discharge, the morphology thereof does not change significantly. The next discharge starts immediately after the pulse current generating circuit (10) completes energy storage.

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