A composite field modulation microwave cold plasma jet device

Abstract

The present invention provides a composite field-modulated microwave cold plasma jet device, which includes a cavity part, a microwave coupling part, a tuning part, and an electric field modulation part; the cavity part is a coaxial resonant cavity structure with one end open, and the microwave transmission mode is the TEM mode; the microwave coupling part can couple microwave energy into the cavity part in ways such as conductance coupling, capacitance coupling, and magnetic field coupling; the electric field modulation part is realized by an inner electrode applying a nanosecond pulse (or DC voltage). Based on the characteristics that microwave cold plasma has less ozone generation, higher plasma concentration, richer excited-state particles, and it is easier to form a long and straight cold plasma with a nanosecond pulse (or DC), the present invention proposes a cold plasma jet with composite field modulation, that is, an auxiliary electric field is applied to the microwave cold plasma, and the auxiliary electric field is used to traction charged particles to accelerate and extend the length of the jet.

Description

Technical Field

[0001] The present invention belongs to the fields of material processing, material detection, plasma biomedicine, clinical medicine, etc. Specifically, it relates to a composite field modulated microwave cold plasma jet device that can obtain a stable atmospheric pressure long straight microwave plasma jet. Background Art

[0002] Plasma is composed of electrons, ions, neutral particles, etc. When the temperature of heavy particles is much lower than that of electrons, it is called cold plasma. At present, atmospheric pressure cold plasma is widely used in the fields of waste gas treatment, assisted combustion, surface modification, medical sterilization, clinical medicine, etc. Among them, the atmospheric pressure cold plasma jet is generated in an open space. While transporting active substances and charged particles, it also separates the discharge area and the working area, with higher safety. Therefore, it has good application prospects in the fields of biology, clinical medicine, etc. In practical applications, the jet length is the key parameter to be considered first, which greatly affects and restricts the application of the atmospheric pressure cold plasma jet. At the same time, the plasma composition is also a key factor to be considered, which limits the application scenarios of the plasma jet.

[0003] Cold plasma can be generated by driving corresponding devices through high voltage, microwave, radio frequency, etc. The driving method and device structure have an important impact on the jet length and composition. Among them, the microwave cold plasma jet has the advantages of large electron density, high ionization degree, strong controllability, and low ozone generation amount, and can be efficiently applied to various scenarios such as germ inactivation, wound treatment, and human surgery.

[0004] The cold plasma jet is generated in an open space, and the influx of air results in a short jet length. To solve this problem, there are currently three ways to extend the jet length.

[0005] One is to use a large flow of inert gas (helium, argon, neon, etc.) as the working gas, so that the jet nozzle is in an inert gas environment with a relatively low breakdown field strength threshold, which is conducive to plasma formation. At the same time, the high flow of gas can pull the plasma outwards;

[0006] The second is to drive by high-voltage nanosecond pulses. Under extremely high and extremely fast energy input, a significant increase in the plasma jet length has been observed;

[0007] The third is to adopt a composite coaxial double-line structure to regulate the plasma jet shape in the way of double resonant cavities cooperating with double gas flow constraints. (Corresponding patent number: CN201910658894.6).

[0008] 1) When using inert gas as the working gas, a large gas cylinder is required, which is inconvenient to carry and is not suitable for outdoor, grounded material collection and other working environments. In addition, the plasma jet is not suitable for some special environments (such as lung treatment, etc.);

[0009] 2) Among the commonly used working gases, air has a wider application prospect because it does not need to be equipped with gas cylinders, is portable and easy to operate, etc., but it also has problems such as the breakdown field strength threshold is much greater than that of inert gases, and a large amount of ozone is generated when the discharge is stimulated by using high-voltage driven dielectric barrier discharge and other methods. When applied to clinical medicine, it is not conducive to the health of the treated objects;

[0010] 3) When the plasma jet is ejected by airflow, the pathogens and other medical objects being treated may be separated from their positions due to the disturbance of airflow, which may cause potential problems of biochemical contamination;

[0011] 4) When a microwave cold plasma jet is generated by a composite coaxial double-line and double-gas flow method, since the open ends are all straight tube structures, the electric field strength is not further enhanced, and it is difficult to reach the excitation field strength of air microwave cold plasma, which restricts its application when air is the working gas. Summary of the invention

[0012] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a composite field modulated microwave cold plasma jet device, which uses a microwave source to drive a dual-resonance cavity structure to generate a normal-pressure cold plasma jet, and on this basis introduces an auxiliary electric field formed by high pressure to pull the extremely dense charged particles in the microwave plasma to move out of the nozzle, thereby extending the jet length.

[0013] The present invention can be implemented through the following technical solutions:

[0014] A composite field modulated microwave cold plasma jet device, consisting of a cavity part, a microwave coupling part, a tuning part and an electric field modulation part;

[0015] The cavity part is an outer tube with one end open, a middle tube with two ends open, and an inner electrode coaxial resonant cavity structure, the outer tube is provided with a microwave feeding port, a tangential flow shielding gas inlet and a gas inlet, and the outer tube is grounded;

[0016] The microwave coupling part includes a coupling ring, which couples microwave energy to the cavity part;

[0017] The tuning part is a structure for adjusting the length of the resonant cavity at the tuning end to adjust the field strength at the open end, and the upper end of the tuning end is a reflective end surface; the depth of the cavity part adjusted to the tuning end is Mλ / 4, where λ is the wavelength at the microwave frequency, and M is a positive odd number;

[0018] The electric field modulation part is connected to the inner electrode by a nanosecond pulse / DC voltage.

[0019] Furthermore, the outer tube, the middle tube, and the inner electrode are all made of metal. The outer tube, the middle tube, and the reflection end form a coaxial resonator with one end open. The middle tube and the inner electrode are of coaxial line structure, and microwaves are all transmitted in TEM mode. A TEM standing wave field is formed inside the former, and a traveling wave field is formed in the latter.

[0020] Furthermore, the axial length of the outer tube is Nλ / 4, where λ is the wavelength at the microwave frequency and N is a positive odd number.

[0021] Furthermore, the upper ports of the outer tube and the middle tube are of a gradually tapered closing structure. The outer tube is tapered by 0 to 60°, and the middle tube is tapered by 0 to 30°.

[0022] Furthermore, there is a porous coaxial washer made of insulating material between the middle tube and the inner electrode.

[0023] Furthermore, the upper port of the middle tube is not higher than the outer tube, and the upper end of the inner electrode is not lower than the middle tube.

[0024] Furthermore, the outer tube and the middle tube introduce gas through the shielding gas inlet or the gas inlet.

[0025] Furthermore, the shielding gas is introduced in a tangential flow manner at the shielding gas inlet; the gas flow rates at the shielding gas inlet and the gas inlet are controlled within 0 to 20 L / min.

[0026] Furthermore, the distance between the coupling ring and the upper port of the outer tube is adjustable; the applicable electromagnetic wave frequency range of the microwave plasma jet device is from several MHz to several GHz.

[0027] Furthermore, the output pulse width of the nanosecond pulse power supply is 10 to 900 ns, the rising edge is 1 to 200 ns, the amplitude is 3 to 220 kV, the frequency is 1 to 20 kHz, and the duty cycle is 1 to 99%; the output voltage of the DC power supply is 0 to 60 kV or 0 to -60 kV.

[0028] Beneficial effects

[0029] In the present invention, the electric field dominates and drives the movement of charged particles, effectively avoiding the possible biochemical contamination caused by air flow disturbance. At the same time, the high voltage can drive the generation of cold plasma, which can assist ignition at the torch tube port, facilitating the formation of the microwave plasma jet and improving its stability. Among them, due to the large difference in the working frequencies between the nanosecond pulse / DC high voltage and the microwave, the DC electric field and the microwave field can be decoupled in the plasma resonator. In addition, the microwave cold plasma generation device is based on the deformation of the microwave plasma torch (MPT), and a gradually tapered closing structure is added to the upper ends of the outer tube and the middle tube to regulate the electric field at the open end.

[0030] With the above structure, a stable microwave cold plasma jet with a length of 5 - 40 mm can be generated, the microwave power conversion efficiency is higher than 80%, and the present invention integrates microwave generation, auxiliary electric field, auxiliary ignition, etc., greatly reducing the overall volume, being light in weight, portable, having a low ozone generation amount, and being applicable to special environments such as outdoors, local material utilization, and enclosed spaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic structural diagram of the present invention DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following describes the embodiments of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Specific Embodiment 1

[0034] Specific Embodiment 1 provides a composite field modulated microwave cold plasma jet device of the present invention, and a typical structural diagram is given in combination with Figure 1 A typical structural diagram is given.

[0035] The composite field modulated microwave cold plasma jet device is composed of a cavity part, a microwave coupling part, a tuning part, and an electric field modulation part;

[0036] See Figure 1 , the composite field modulated microwave cold plasma jet device of the present invention includes a microwave feeding port 1, an outer tube 2, a tuning end 3, a middle tube 4, an inner electrode 5, a coupling ring 6, an insulating dielectric porous coaxial gasket 7, a tangential flow shielding gas inlet 8, a nanosecond pulse / DC high voltage input end 9, and a gas inlet 10;

[0037] The cavity part is a coaxial resonant cavity structure of an outer tube 2, a middle tube 4, and an inner electrode 5;

[0038] The outer tube, middle tube, and inner electrode are all made of metal. The outer tube, middle tube, and reflection end form a coaxial resonant cavity with one end open. The middle tube and inner electrode are coaxial line structures, and the microwave is transmitted in the TEM mode. The former forms a TEM standing wave field inside, and the latter is a traveling wave field;

[0039] The inner electrode is connected to an auxiliary power supply (DC or nanosecond pulse modulation source);

[0040] The axial length of the outer tube is Nλ / 4 (λ is the wavelength at the microwave frequency, and N is a positive odd number);

[0041] The upper ports of the outer tube and the middle tube are of a gradually tapered structure. The outer tube is tapered by 0 - 60°, and the middle tube is tapered by 0 - 30°. This design is used to adjust the electric field at the port;

[0042] There is a porous coaxial washer made of insulating material between the middle tube and the inner electrode;

[0043] The upper port of the middle tube is not higher than that of the outer tube, and the upper end of the inner electrode is not lower than that of the middle tube. Preferably, the upper end of the middle tube is 0 - 2 mm lower than the upper port of the outer tube, and the upper end of the inner electrode is 0 - 5 mm higher than the upper port of the middle tube; Figure 1 The upper ends of the middle and inner electrodes are flush with the upper port of the outer tube;

[0044] The outer tube and the middle tube can introduce shielding gas. Preferably, the gas is introduced in a tangential flow manner at the gas inlet 8; the gas flow rates of the gas inlet 8 and the gas inlet 10 are controlled within 0 - 20 L / min;

[0045] The microwave coupling part can couple microwave energy to the cavity part in ways such as conductance coupling and capacitance coupling; Figure 1 The structure diagram of introducing microwave energy into the resonant cavity by conductance coupling is given; the distance between the coupling ring 6 and the upper port of the outer tube is adjustable; the applicable electromagnetic wave frequency range of the microwave plasma jet device is several MHz to several GHz. Preferably, a stable atmospheric pressure microwave cold plasma jet with a length of 5 - 40 mm is generated at a frequency of 2.45 GHz, and the microwave power conversion efficiency is greater than 80%.

[0046] The tuning part is a structure for adjusting the length of the resonant cavity by the tuning end 3 to adjust the field strength at the open end. The upper end of the tuning end is a reflecting end face, and its material is a metal material; the depth of the tuning end adjusted into the cavity part is Mλ / 4 (λ is the wavelength at the microwave frequency, and M is a positive odd number);

[0047] The electric field modulation part is that the auxiliary power supply (nanosecond pulse or DC high voltage) is connected to the inner electrode 5, and the ground wire is connected to the outer tube; the output pulse width of the nanosecond pulse power supply is 10 - 900 ns, the rising edge is 1 - 200 ns, the amplitude is 3 - 220 kV, the frequency is 1 - 20 kHz, and the duty cycle is 1 - 99%; the output voltage of the DC power supply is 0 - 60 kV or 0 - -60 kV;

[0048] The described microwave plasma jet device can work in the following 14 methods:

[0049] 1) Microwave is coupled to the resonant cavity through the microwave coupling part, forming a TEM standing wave in the resonant cavity. The nanosecond pulse power supply is connected to the inner electrode, and plasma is formed at the axis position of the upper port of the resonant cavity and is ejected outward under the drive of the pulsed electric field;

[0050] 2) Microwave is coupled to the resonant cavity through the microwave coupling part, forming a TEM standing wave in the resonant cavity. The high - voltage (positive / negative) power supply is connected to the inner electrode, and plasma is formed at the axis position of the upper port of the resonant cavity and is ejected outward under the drive of the high - voltage electric field;

[0051] 3) Microwaves are coupled into the resonant cavity through the microwave coupling part, forming a TEM standing wave in the resonant cavity. Plasma is formed at the axis position of the upper port of the resonant cavity and ejected outward;

[0052] 4) The nanosecond pulse power supply is connected to the inner electrode. Plasma is formed at the tip position of the inner electrode and ejected outward;

[0053] 5) The DC high voltage (positive / negative) power supply is connected to the inner electrode. Plasma is formed at the tip position of the inner electrode and ejected outward;

[0054] 6) Based on Method 1), the outer tube is not connected to the ground wire, and the infinite far end is used as the ground wire;

[0055] 7) Based on Method 2), the outer tube is not connected to the ground wire, and the infinite far end is used as the ground wire;

[0056] 8) Based on Method 4), the outer tube is not connected to the ground wire, and the infinite far end is used as the ground wire;

[0057] 9) Based on Method 5), the outer tube is not connected to the ground wire, and the infinite far end is used as the ground wire;

[0058] 10) Based on Method 1), the gas (single / mixed) is input from Inlet 8 and Inlet 10, synergistically driving the microwave plasma jet to eject with the pulsed electric field, and adjusting the plasma composition;

[0059] 11) Based on Method 2), the gas (single / mixed) is input from Inlet 8 and Inlet 10, synergistically driving the microwave plasma jet to eject with the high voltage electric field, and adjusting the plasma composition;

[0060] 12) Based on Method 3), the gas (single / mixed) is input from Inlet 8 and Inlet 10, pulling the microwave plasma jet to eject, and adjusting the plasma composition;

[0061] 13) Based on Method 4), the gas (single / mixed) is input from Inlet 8 and Inlet 10, pulling the cold plasma jet driven by the nanosecond pulse to eject, and adjusting the plasma composition;

[0062] 14) Based on Method 5), the gas (single / mixed) is input from Inlet 8 and Inlet 10, pulling the cold plasma jet driven by the DC high voltage to eject, and adjusting the plasma composition.

[0063] The present invention extends the length of the microwave cold plasma jet. By coordinating different driving parameters and gas parameters, specific cold plasma can be generated intelligently, improving its operability and practicality in fields such as clinical hospitals.

[0064] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations, modifications and various combinations with the above specific embodiments within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A composite field modulated microwave cold plasma jet device, characterized in that, It consists of a cavity part, a microwave coupling part, a tuning part, and an electric field modulation part; The cavity part is a structure of an outer tube with one end open, a middle tube with both ends open, and an inner electrode coaxial resonator. The outer tube is provided with a microwave feeding port, a tangential flow shielding gas inlet, and a gas inlet, and the outer tube is grounded; The microwave coupling part includes a coupling ring for coupling microwave energy into the cavity part; The tuning part is a structure for adjusting the length of the resonator by the tuning end to adjust the field strength at the open end. The upper end of the tuning end is a reflecting end face; the depth of the tuning end adjusted into the cavity part is Ml / 4, where l is the wavelength at the microwave frequency and M is a positive odd number; The electric field modulation part is connected to the inner electrode by a nanosecond pulse or DC voltage; the outer tube, the middle tube, and the inner electrode are all made of metal. The outer tube, the middle tube, and the reflecting end form a coaxial resonator with one end open. The middle tube and the inner electrode are coaxial line structures, and the microwave is transmitted in the TEM mode. A TEM standing wave field is formed inside the former, and a traveling wave field is formed in the latter; the axial length of the outer tube is Nl / 4, where l is the wavelength at the microwave frequency and N is a positive odd number; The upper ports of the outer tube and the middle tube are of a gradually tapered structure. The taper angle of the outer tube is 0 to 60°, and the taper angle of the middle tube is 0 to 30°.

2. The composite field modulated microwave cold plasma jet device according to claim 1, wherein There is a porous coaxial washer made of insulating material between the middle tube and the inner electrode.

3. A composite field modulation microwave cold plasma jet device according to claim 1, characterized in that, The upper port of the middle tube is not higher than that of the outer tube, and the upper end of the inner electrode is not lower than that of the middle tube.

4. A composite field modulated microwave cold plasma jet device according to claim 1, characterized in that, The outer tube and the middle tube introduce gas through the shielding gas inlet or the gas inlet.

5. A composite field modulated microwave cold plasma jet device according to claim 1, characterized in that, The shielding gas is introduced in a tangential flow manner at the shielding gas inlet; the gas flow rates of the shielding gas inlet and the gas inlet are controlled within 0 to 20 L / min.

6. A composite field modulated microwave cold plasma jet device according to claim 1, characterized in that, The distance between the coupling ring and the upper port of the outer tube is adjustable; the applicable electromagnetic wave frequency range of the microwave cold plasma jet device is several MHz to several GHz.

7. A composite field modulated microwave cold plasma jet device according to claim 1, characterized in that, The output pulse width of the nanosecond pulse power supply is 10 to 900 ns, the rising edge is 1 to 200 ns, the amplitude is 3 to 220 kV, the frequency is 1 to 20 kHz, and the duty cycle is 1 to 99%; the output voltage of the DC power supply is 0 to 60 kV or 0 to -60 kV.

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