CN115235301B - Ignition device and ignition method for low-power hollow cathode micro plasma - Google Patents

Abstract

The invention discloses an ignition method and an ignition device for low-power hollow cathode microplasma. The device consists of a miniature high-voltage conversion unit and a miniature plasma generation unit, wherein the miniature high-voltage conversion unit realizes that low-voltage direct current input is converted into high-voltage direct current, alternating current or pulse output; the micro plasma generating unit adopts a sandwich structure consisting of an upper electrode, a lower electrode and an insulating medium in the middle, and one or more holes penetrating the electrodes and the insulating medium are arranged on the sandwich structure to serve as a plasma generating area. The device converts a low-voltage direct-current starting signal into high-voltage output by utilizing a miniature high-voltage conversion unit, and the high-voltage drives a plasma generation unit to generate air unbalanced plasma so as to ignite energetic grains embedded into micropores or an energetic film adhered above the micropores to realize ignition. The device has the characteristics of high safety and reliability, low ignition power and capability of being ignited for multiple times.

Description

Ignition device and ignition method for low-power hollow cathode micro plasma

Technical Field

The invention belongs to the field of ignition of explosive devices, and more specifically, relates to an ignition device and an ignition method for low-power hollow cathode micro plasma.

Background technique

Initiators are the general term for components, devices and systems that, after receiving control information, stimulate pyrotechnic agents to burn or explode with relatively small amounts of energy, and are used to ignite gunpowder, detonate explosives, perform mechanical work or produce special effects. As the initial ignition source, the ignition device is the bridge between the issuance of commands and the achievement of goals. Whether it can function reliably is directly related to whether the initiators and subsequent systems can ignite or detonate normally.

Gas discharge plasma provides a new way for ignition. Gas discharge generates plasma by applying high voltage to the gas, causing the gas to undergo breakdown discharge. Under the action of a strong electric field, the drift motion of electrons is significantly stronger than that of other particles, which makes the electron temperature very high. For example, the electron energy can reach more than 1eV (1eV is equivalent to 11600K), and there are a large number of active nitrogen and oxygen particles (such as N atoms, O atoms, OH molecules, NO molecules, etc.) acting as combustion aids, so it has unique advantages in ignition.

At present, the existing ignition devices in China are still mainly based on sensitive bridge wires, which have low structural strength, poor heat dissipation performance, weak anti-electromagnetic ability, low safety current, and great difficulty in integration with digital logic circuits, which seriously restricts the further development of my country's micro-intelligent weapons and aerospace technology. Some new ignition devices such as semiconductor bridges and explosive foils have not yet been widely used. Among them, semiconductor bridges mainly ignite polysilicon bridges through thermal ionization, while explosive foils generate plasma through thermal ionization bridge foils, and impact flying pieces ignite. The above-mentioned ignition devices are based on thermal ionization to generate plasma rather than gas discharge, and are therefore significantly different from the present invention.

By regulating the density of high-energy electrons and highly active nitrogen and oxygen particles in the plasma, it can be made suitable for the ignition requirements of energetic agents with different sensitivities. At present, domestic pyrotechnics are still dominated by second-generation sensitive bridge pyrotechnics, which have poor safety; conventional third-generation semiconductor bridge pyrotechnics can meet the Class A insensitivity requirements of 1A1W5min without ignition; and explosive foil pyrotechnics can meet the Class B insensitivity requirements of 500V without ignition. Therefore, the above-mentioned ignition device can only be applied to a specific range, and based on the gas discharge microplasma ignition technology, by changing the output voltage and discharge structure, the characteristic parameters such as plasma electron density, electron temperature and active particle density can be efficiently regulated, thereby realizing the reliable ignition of specific insensitive energetic agents.

In the existing plasma ignition technology, the plasma ignition method and plasma generating device described in patent CN13796163A are actually methods and devices for generating plasma, and the working gas described therein is not air. Patent CN214675822U provides a microwave plasma ignition device, but it uses microwave plasma, which is significantly different from the present invention. In addition, its working gas and specific application direction are unclear, and it does not belong to the field of ignition of explosives described in the present invention. Patent CN214674348U provides a plasma ignition power supply system, but it is also a method for generating plasma, and it needs to rely on strong magnetic field control, which is significantly different from the present invention. In short, the above-mentioned plasma ignition technology mainly refers to the method of generating plasma, rather than using plasma to ignite or detonate energetic agents. Patent CN110475309A introduces a programmable plasma point piston, which is mainly used as an ignition source for internal combustion engines, but its operating voltage reaches tens of kilovolts, and the working gas is a mixture of air and fuel (such as gasoline), that is, by directly converting energetic molecules into plasma, which is also significantly different from the present invention.

Summary of the invention

In view of the limitations of existing ignition technology, the purpose of the present invention is to design a new ignition device to achieve reliable ignition of conventional detonators and sensitive explosives, and the ignition device has the advantages of adjustable ignition performance, simple structure, low input power, etc.

In order to achieve the above-mentioned purpose, a low-power hollow cathode micro plasma ignition device and ignition method are provided, which include a micro high-voltage conversion unit and a micro plasma generation unit, wherein the input end of the micro plasma generation unit is connected to the output end of the micro high-voltage conversion unit.

The core ignition mechanism of the hollow cathode plasma discharge ignition device of the present invention is:

Relying on a miniature high-voltage conversion unit, a transient high voltage is applied to the air to cause gas discharge, thereby generating a non-equilibrium plasma. The energy is transferred by bombarding the energetic agent with high-energy electrons generated in the plasma. At the same time, the active nitrogen and oxygen particles in the plasma provide highly active oxidants for the energetic agent. The synergistic effect of the key components in the above plasma is used to achieve the ignition of the energetic agent.

Furthermore, the miniature high-voltage conversion unit includes a rectifier circuit and a boost circuit, and its overall shape can be a cylinder or a cuboid, the diameter of the cylinder is ≥3cm, and the height is ≥10cm; the length and width of the cuboid are ≥3cm, and the height is ≥10cm.

Furthermore, the driving voltage of the micro high-voltage conversion unit is in direct current form, and the input voltage amplitude is between 1.5V and 12V.

Furthermore, the output voltage of the micro high-voltage conversion unit may have a voltage waveform in the form of direct current, alternating current, or pulse.

Furthermore, the DC voltage amplitude is 1kV-30kV; the peak-to-peak value of the AC voltage is 1kV-30kV, and the frequency is 50Hz-300MHz; the pulse voltage amplitude is 1kV-30kV, the rising edge: ≥100μs, and the frequency is 50Hz-300MHz.

The micro plasma generating unit is a hollow cathode structure, which adopts a sandwich structure composed of two upper and lower metal electrodes and an insulating medium in the middle, and has one or more holes penetrating the electrodes and the insulating medium.

Furthermore, the metal electrode material may be copper, silver, aluminum, tungsten, platinum and the like, and the dielectric material may be inorganic non-metallic materials such as _SiO2 , metal oxide materials such as _{Al2O3 ,} and organic non-metallic materials including PCB substrates.

Furthermore, the distance between the two electrodes is ≥1 mm, the diameter of the micropores on the electrodes is ≥2 mm, and the diameter of the micropores in the dielectric layer is ≥10 mm.

After applying high voltage to both ends of the electrode, the plasma generating unit causes breakdown discharge of the gas in the micropores to generate plasma. Preferably, the typical working gas is air. Therefore, the corresponding plasma is air plasma.

Furthermore, microplasma refers to plasma that is smaller than 1 mm in a certain dimension.

Furthermore, by changing the voltage output of the conversion unit and the electrode spacing of the generation unit, the following characteristic parameters of the plasma can be controlled: (1) Peak electron temperature: 1eV-10eV. (2) The adjustable range of electron and ion density is 10 ¹² /cm ³ -10 ¹⁶ /cm ^3. (3) Typical active nitrogen and oxygen particles ≤10 ¹² /cm ³ , including nitrogen ions (N ₂ ⁺ ), oxygen ions (O ₂ ⁺ ), nitrogen atoms (N), oxygen atoms (O), ozone (O ₃ ), etc.

The working principle of the ignition device based on hollow cathode discharge of the present invention is:

(1) Load the energetic agent into the plasma generating area.

(2) Connect the electrode to the output terminal of a high voltage power supply.

(3) Turn on the power supply, and the micro high-voltage conversion unit generates high voltage which is input to the micro plasma generating unit, forming a transient high voltage between the electrodes and generating plasma in the discharge area.

(4) Microplasma acts on energetic agents to achieve ignition.

(5) If the energetic agent needs to be replaced, repeat steps (1) to (4).

In summary, the air microplasma of the present invention has the following characteristics:

(1) Non-equilibrium output characteristics: Due to the strong electric field under the action of high voltage, the electrical energy is preferentially transmitted to electrons, resulting in the plasma having significant non-equilibrium characteristics, and the electron temperature is much higher than the gas temperature.

(2) High and adjustable electron and ion density: The electron and ion density of the air plasma of the present invention is adjustable in the range of 10 ¹² /cm ³ -10 ¹⁶ /cm ³ , and the peak electron density ranges from 1eV to 10eV.

(3) Highly active combustion-supporting ability: In the air discharge, the high-energy electrons in the plasma are accompanied by a large number of excitation and decomposition processes in the process of ionizing atoms and molecules. Therefore, there are a large number of active nitrogen and oxygen particles in the plasma, including ground state atoms: such as nitrogen atoms (N) and oxygen atoms (O); ground state molecules: such as oxygen molecules (O ₂ ) and ozone (O ₃ ); excited state particles: the excited state forms corresponding to the above ground state particles, such as excited oxygen atoms (O1s, O1d, N1p, etc.), singlet oxygen ( ¹ O ₂ ), etc. Ground state or excited state ions: such as oxygen anions (O ^- ) and superoxide anions (O ^2- ). These particles have extremely high oxidation ability and a density of ≤10 ¹² /cm ³ , and can act as combustion-supporting agents, thereby realizing chemical reactions that are difficult to occur under ordinary thermodynamic conditions and improving ignition ability.

(4) Transient response capability: The response time of air discharge plasma is closely related to the discharge gap voltage. When a high voltage is applied to both ends of the electrode, the electrons are accelerated under the action of the strong electric field to gain kinetic energy to collide with atoms and molecules. For air gaps at the millimeter level, the plasma generation process is ≥10μs.

Furthermore, the energetic agent described in the device includes conventional detonating agents (such as lead styphnate, etc.) and nano-thermite.

Preferably, the electrode material of the plasma generating device is copper, the electrode thickness is ≥1mm, the diameter is 0.5mm-10mm, the discharge hole diameter is 0.1mm-1mm, and the distance between the pin and the axis is 1mm-2mm.

Preferably, the insulating dielectric material of the plasma generating device is alumina, with a thickness of ≥1 mm, a diameter of 0.5 mm-12 mm, a diameter of the axial discharge hole of 0.1 mm-1 mm, and a distance between the pin hole and the axis of 1 mm-2 mm.

In general, the ignition device implemented by the present invention can achieve the following beneficial effects compared with the existing device:

(1) Good safety and reliability: Different from the linear energy conversion method of conventional electric thermal ignition devices, the new ignition device based on air discharge microplasma has a special nonlinear energy conversion characteristic - when the external applied voltage is less than the gas breakdown voltage, plasma will not be generated, and when the external applied voltage exceeds the plasma breakdown voltage, the gas will undergo avalanche ionization to form plasma, completing the nonlinear conversion of electrical energy into kinetic energy, molecular and atomic potential energy, and radiation energy.

(2) Good ignition effect: The plasma generated by the ignition device has high electron and ion density, high electron temperature, and high active nitrogen and oxygen particle concentration ≤10 ¹³ /cm ³ . High electron density and high electron temperature are the key to igniting energetic agents, while active nitrogen and oxygen particles have a combustion-supporting effect, which can make the agent burn more fully. The ignition effect is observed to be equivalent to that of a semiconductor bridge.

(3) Adjustable ignition performance: Compared with conventional ignition devices such as sensitive bridge wires, semiconductor bridges, and exploding foils, the ignition performance control of the ignition device of the present invention only requires adjusting the electrode spacing and input voltage parameters, thereby meeting the reliable ignition of specific insensitive energetic agents. For example, the sensitivity of thermite is relatively high, and ignition can be achieved in the normal plasma working mode. For ignition agents such as boron/potassium nitrate, the sensitivity is relatively low, and the plasma power needs to be significantly increased to ≤20W. In addition, compared with the above-mentioned pyrotechnics, it also has the advantages of long service life and multiple ignitions.

(4) Simple structure: The material cost and maintenance cost of this device are very low, and it is economical; no additional ventilation is required during operation, avoiding the need to carry gas cylinders.

(5) Low power, low input voltage requirements, no need to carry high-power power supply equipment, and good portability and assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the device of the present invention.

FIG. 2 shows another form of the micro plasma generating unit in the device of the present invention.

FIG. 3 shows two other forms of the micro plasma generating units in the device of the present invention (a is the array form of form 1, and b is the array form of form 2).

Figure 4 is an embodiment of thin film charging of the micro plasma generating unit in the device of the present invention (a is a film-type charge of form one, b is a film-type charge of form two, c is a film-type charge of form one array, and d is a film-type charge of form two array).

Figure 5 is an embodiment of charging in holes of a micro plasma generating unit in the device of the present invention (a is columnar charging of form one, b is columnar charging of form two, c is columnar charging of form one array, and d is columnar charging of form two array).

Figure 6 Schematic diagram of a micro high voltage conversion unit module.

FIG7 is a typical discharge voltage-current characteristic diagram of the device.

FIG8 is a diagram showing the effect of the device igniting thermite.

In all the drawings, the same figure numbers are used to represent the same elements or structures, among which: 1-micro high-voltage conversion unit, 2-unit interface, 3-lower electrode pin, 4-upper electrode pin, 5-lower electrode, 6-insulating medium, 7-upper electrode, 8-discharge hole, 9-energetic material, 10-rectifier circuit, 11-voltage doubling circuit module.

Detailed ways

To further illustrate the present invention, a specific implementation manner of a low-power ignition device and method based on hollow cathode discharge proposed by the present invention is described in detail below in conjunction with the accompanying drawings.

The plasma ignition device is mainly composed of two units, including a micro high-voltage conversion unit and a micro plasma generation unit, wherein the input end of the micro plasma generation unit is connected to the output end of the micro high-voltage conversion unit. The micro high-voltage conversion unit belongs to the excitation power supply part, which transmits energy to the micro plasma generation unit by generating high voltage in the form of direct current, high-frequency alternating current and pulse; the micro plasma generation unit is designed with a special structure so that the voltage loaded on both ends of the electrode is sufficient to break through the air inside the discharge hole, so that the gas breaks down to generate discharge and plasma, and the high-energy electrons and active particles in the plasma are used to ignite the energetic agent.

The design core of this device lies in the design of the micro high-voltage conversion unit and the structural design of the plasma generation unit. Among them, the design core of the micro high-voltage conversion unit is to convert the input energy of low voltage and high current into high-voltage energy. The design core of the micro plasma generation unit is to control the distance between electrodes and design the discharge hole.

Based on this, the present invention provides a low-power ignition device and ignition method based on hollow cathode discharge, as shown in FIG1 , which is an embodiment 1 of the present invention.

A low-power ignition device based on hollow cathode discharge consists of two parts, as shown in FIG6 . In this embodiment, the micro high-voltage conversion unit 1 consists of a rectifier circuit 10 and a voltage doubler circuit 11 , wherein the rectifier circuit 10 is a single-tube self-excited rectifier circuit composed of a triode and a transformer winding, and the collector voltage of the triode forms positive feedback through a resistor and a feedback winding on the transformer. When the low-voltage input power supply is energized for the high-voltage conversion unit, since the current at both ends of the inductor cannot change suddenly, the triode quickly enters the saturation state from the cut-off state. At this time, the collector voltage drops and causes the base current to decrease, and the triode quickly enters the cut-off state from the saturation state. The whole process repeats itself, thereby converting direct current into high-frequency alternating current and applying it to the primary winding of the transformer. The high-frequency alternating current generated by the rectifier circuit is boosted by the transformer and then input into the voltage doubler circuit for boost rectification. The voltage doubler circuit utilizes the diode guidance effect to store the voltage in each capacitor respectively, and then connects several capacitors in series to form a voltage superposition, and finally applies the obtained high-voltage alternating current to the unit interface 2 and inputs it into the micro plasma generating unit.

In this embodiment, the plasma generating unit is composed of two upper and lower electrodes and an insulating medium in the middle. The electrode material can be copper, silver, aluminum, tungsten, platinum and other materials, and the shape is circular. The upper electrode 7 is connected to a wire as a pin at a certain distance from the axis. The distance depends on the discharge aperture size, the electrode and the insulating medium material and thickness, and the typical distance is ≤0.5mm. The upper electrode pin 4 passes through the insulating medium 6 and the pin hole reserved on the lower electrode 5 and is connected to the micro-boosting device unit interface 2. A discharge hole 8 is reserved at the axis of the upper electrode 7. The lower electrode 5 is made of the same material as the upper electrode 5, and has a pin at a central symmetric position with the pin of the upper electrode 7, which is connected to the micro-boosting device unit interface 2. The insulating medium 6 is a non-metallic oxide material such as _SiO2 , a metal oxide material such as _{Al2O3 ,} and an organic non-metallic material including a PCB substrate, etc., and is circular in shape. Its radius should be slightly larger than the upper and lower electrode sheets. A discharge hole 8 is opened at the axis, and a through hole is opened at the pin corresponding to the upper electrode 7, and a sleeve is connected to separate the upper electrode pin from the lower electrode. The axis of the upper and lower electrodes and the insulating medium 6 should be kept in the same straight line to keep the discharge hole 8 connected. When the micro high-voltage conversion unit 1 applies high frequency and high voltage to the upper and lower electrodes, the strong electric field formed first ionizes the air to generate plasma, in which electrons oscillate between two opposite cathode drop regions, resulting in a high ionization and excitation rate, which further strengthens the ionization and generates more high-energy particles. Since there is no wire connection in its working area, its electromagnetic protection capability is enhanced.

A method for igniting a low-power hollow cathode micro-plasma discharge comprises the following steps:

S1. Loading energetic agent 9 into the plasma generating area.

S2. Input low voltage DC signal to the micro high voltage conversion unit

S3. The micro high voltage conversion unit converts the start signal into a high voltage output

S4. A high voltage driven plasma generating unit generates non-equilibrium plasma by breaking down the gas in the hole, thereby igniting the thermite film or charge column installed thereon.

S5. If the energetic agent needs to be replaced, repeat S1-S4.

Specifically, the low-voltage and high-current start-up signal in step S1 is a DC signal, and its voltage range is 1.5V-12V.

Specifically, the output signal in step S2 of this embodiment may be an AC signal, the peak-to-peak value of which is in the range of 1 kV-30 kV, and the current signal is a nonlinear sudden change current.

Specifically, the film-type charging method and column-type charging method in this embodiment are shown in FIG. 4 and FIG. 5 , respectively.

In this embodiment, when 3V, 1A of energy is input to the micro high voltage conversion unit, the volt-ampere characteristic curve when plasma is generated is shown in Figure 7. The ignition effect is shown in Figure 8, which shows that it can reliably ignite the agent, and its flame height is comparable to the semiconductor bridge ignition effect.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any professional and technical personnel familiar with the present invention can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims (9)

1. A low-power hollow cathode micro plasma ignition device, characterized in that it comprises: a micro high-voltage conversion unit and a micro plasma generating unit; the micro plasma generating unit adopts a sandwich structure composed of two upper and lower electrodes and an insulating medium in the middle, and has one or more holes penetrating the electrodes and the insulating medium as a plasma generating area; the distance between the two electrodes is ≥1mm, and the diameter of the electrode micropores is ≥1mm; wherein the input end of the micro plasma generating unit is connected to the output end of the micro high-voltage conversion unit; the upper electrode is connected with a wire as a pin at a certain distance from the axis, the upper electrode pin passes through the insulating medium layer and the pin hole reserved on the lower electrode and is connected to the interface of the micro booster device unit, the lower electrode has a pin at a central symmetric position with the upper electrode pin, connected to the interface of the micro booster device output unit, the insulating medium and the upper electrode corresponding pin are provided with a through hole, and a sleeve is connected to separate the upper electrode pin from the lower electrode. 2. According to claim 1, the ignition device of the low-power hollow cathode microplasma is characterized in that the micro high-voltage conversion unit comprises a rectifier circuit and a boost circuit, and its overall shape is a cylinder or a cuboid, the diameter of the cylinder is ≥3cm, and the height is ≥10cm; the length and width of the cuboid are ≥3cm, and the height is ≥10cm; it can increase the voltage at the input end to 1kV-30kV and then output it, its input DC voltage signal is ≥12V, the current is ≥3A, the output voltage is in the form of high voltage DC, AC and pulse, and the total power is ≥36W. 3. The ignition device of low-power hollow cathode microplasma according to claim 1 is characterized in that the electrode material of the micro plasma generating unit is copper, silver, aluminum, tungsten, or platinum, and the insulating medium material is _SiO2 inorganic non-metallic material, _{Al2O3 metal} oxide material, and organic non-metallic material including PCB substrate; the shape of the electrode and the insulating medium is circular, with a thickness of ≥1mm and a diameter of 0.5mm-10mm, and the diameter of the insulating medium material is larger than the diameter of the electrode material. 4. An ignition method using the ignition device of any one of claims 1 to 3 for low-power hollow cathode microplasma, characterized in that it comprises the following steps: S1. Loading the energetic agent into the plasma generating area; S2. Input a low voltage and high current start signal to the micro high voltage conversion unit; S3. The micro high voltage conversion unit converts the low voltage DC start signal into a high voltage output; S4. A high voltage drives the plasma generating unit to generate air non-equilibrium plasma, thereby igniting the energetic charge embedded in the micropores or the energetic film adhered to the micropores to achieve ignition; S5. If the energetic agent needs to be replaced, repeat S1-S4. 5. The ignition method according to claim 4 is characterized in that the input in step S1 is low voltage direct current with a voltage range of 1.5V-12V; and the output in step S2 is high voltage wave direct current, alternating current and pulse form. 6. The ignition method according to claim 4 is characterized in that the DC output voltage amplitude is 1kV-30kV; the peak-to-peak value of the AC output voltage is 1kV-30kV, and the frequency is 50Hz-300MHz; the pulse output voltage amplitude is 1kV-30kV, the rising edge: ≥100μs, and the frequency is 50Hz-300MHz; the plasma discharge current waveform is a nonlinear mutation current, and the ignition has a transient response capability: for an air gap at the millimeter level, the plasma generation process is ≥10μs. 7. The ignition method according to claim 4 is characterized in that the working gas is air, the plasma is a non-equilibrium plasma, and the characteristic parameters include: (1) peak electron temperature: 1eV-10eV; (2) the electron and ion density adjustment range is 10 ¹² /cm ³ -10 ¹⁶ /cm ³ ; (3) typical active nitrogen and oxygen particles ≤10 ¹² /cm ³ , including nitrogen ions (N ₂ ⁺ ), oxygen ions (O ₂ ⁺ ), nitrogen atoms (N), oxygen atoms (O), and ozone (O ₃ ). 8. The ignition method according to claim 4 is characterized in that the energetic agent in step S3 is lead styphnate igniter, thermite pyrotechnic agent or boron/potassium nitrate ignition agent, and the igniter or thermite coated on the surface of the device is attached to the top of the discharge hole in the form of a film, or penetrates into the hole in the form of a charge column. 9. The ignition method according to claim 4, characterized in that the ignition method is multiple ignitions.