A dual-channel atmospheric pressure microwave plasma jet device

Abstract

The invention discloses a dual-channel atmospheric pressure microwave plasma jet device, which belongs to the field of atmospheric pressure microwave plasma jet application; it includes a dual-channel coaxial resonator, a pulse modulated microwave power supply and a gas path input. The dual-channel coaxial resonator is composed of a gas pipeline, a large coaxial cavity and a small coaxial cavity, an SMA interface, a cavity threaded interface, and a hollow coaxial line. The microwave energy of the pulse modulated microwave power supply is generated by a microwave signal generator and transmitted to a microwave power output interface through a power amplifier and a directional coupler. The gas path input includes a gas storage bottle, a pressure reducing valve, a needle valve and a gas flow meter, and the needle valve and the gas flow meter can control the input flow rate of the working gas. The present invention can separate the working gas, realize the spatiotemporal distribution regulation of active particles in the plasma jet, and the density of the active particles generated is large, which can effectively regulate the temperature of the plasma jet and increase the scope of use of the microwave plasma jet.

Description

Technical Field

[0001] The invention relates to the technical field of atmospheric pressure microwave plasma jet application, in particular to a dual-channel atmospheric pressure microwave plasma jet device. Background Art

[0002] Plasma is called the fourth state of matter. It is rich in a large number of highly active particles and is widely used in the fields of material modification, environmental treatment, auxiliary combustion, biomedicine, etc. In actual production, plasma can usually be generated in the form of gas discharge, such as corona discharge, microwave discharge, dielectric barrier discharge, etc. Among them, the plasma generated by microwave discharge has the advantages of high particle activity and high density. It has great application prospects in the fields of auxiliary ignition, chemical element detection, material surface treatment, medical sterilization and wound treatment. However, common atmospheric pressure microwave plasma generation equipment is kilowatt-level and has a complex structure, which is not conducive to energy conservation and miniaturization. The coaxial resonator is a low-power microwave plasma source designed according to the transmission line principle. It can generate and maintain discharge using lower microwave power in an atmospheric pressure environment, and the size of the coaxial resonator is greatly reduced compared to other kilowatt-level microwave discharges.

[0003] The Chinese patent "A coaxial plasma torch and a low-power microwave microplasma excitation device" (application number: 202111232706.7, authorization publication number: CN113923847A, authorization publication date: 2022-01-11) discloses a coaxial plasma torch and a low-power microwave microplasma excitation device, which can reduce the microwave automatic excitation power of the atmospheric pressure microplasma to 10W, while greatly reducing the volume of the structure. However, this device is only suitable for working under a single gas, and the temperature of the plasma jet cannot be adjusted by the microwave power supply, which limits its application range.

[0004] The Chinese patent "An air microwave plasma jet surface treatment device" (application number: 202011110550.0, authorization publication number: CN112135409A, authorization publication date: 2020-12-25) discloses an air microwave plasma jet surface treatment device, which includes a microwave power supply and a cylindrical coaxial resonant cavity. This device can adjust the position of the coaxial line, can better meet the resonance matching, and the device can work under mixed gas, with good practicality. However, when this device works with mixed gas, the working gas will be pre-mixed in the resonant cavity first, and the working gas cannot be separated, and the spatiotemporal distribution adjustment of different active particles in the plasma jet cannot be achieved. Summary of the invention

[0005] The object of the present invention is to provide a dual-channel atmospheric pressure microwave plasma jet device which can achieve the regulation of the spatiotemporal distribution of active particles in a plasma jet and can effectively control the temperature of the plasma jet, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A dual-channel atmospheric pressure microwave plasma jet device, comprising a dual-channel coaxial resonator, a pulse modulated microwave power supply and a gas input; the dual-channel coaxial resonator is composed of a gas pipeline, a large coaxial cavity and a small coaxial cavity, an SMA interface, a cavity thread interface, and a hollow coaxial line; the large coaxial cavity and the small coaxial cavity are combined into a complete resonant cavity through the cavity thread interface, the hollow coaxial line is fixed on the resonator, and the working gas is passed into the resonator and the hollow coaxial line through the gas pipeline; the SMA interface is used for feeding microwave power and generating field strength at the open end;

[0008] The microwave energy of the pulse modulated microwave power supply is generated by a microwave signal generator, and its microwave parameters are manually adjusted by the pulse signal modulator. The microwave energy generated by the microwave signal generator is transmitted to the SMA interface via a power amplifier and a directional coupler;

[0009] The gas circuit input includes a gas storage bottle, a pressure reducing valve, a needle valve and a gas flow meter, and the needle valve and the gas flow meter are used to control the input flow size of the working gas.

[0010] Furthermore, the large coaxial cavity and the small coaxial cavity are made of copper, the outer diameter of the large coaxial cavity is 24mm, the inner diameter is 14mm, and the length is 20mm, the outer diameter of the small coaxial cavity is 10mm, the inner diameter is 8mm, and the length is 30mm, and the outer diameter of the cavity threaded interface is 14mm.

[0011] Furthermore, the resonator composed of the large coaxial cavity and the small coaxial cavity is configured with one end short-circuited and the other end open-circuited, so as to obtain the maximum field strength at the open end after microwave feeding.

[0012] Furthermore, the hollow coaxial line is made of copper, and its inner diameter and outer diameter are 1 mm and 2 mm respectively.

[0013] Furthermore, the SMA interface is 3 mm away from the short-circuit end.

[0014] Furthermore, the gas pipeline is made of plastic material, the inner diameter of the gas inlet end is 4 mm, the outer diameter is 6 mm, and it is fixed to the large coaxial cavity by gluing.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. A dual-channel atmospheric pressure microwave plasma jet device provided by the present invention adds pulse modulation technology to the ordinary microwave power supply technology. The temperature of the plasma jet can be effectively adjusted by controlling the duty cycle and pulse modulation frequency of the pulse modulation, thereby increasing the application range of the microwave plasma jet.

[0017] 2. The present invention provides a dual-channel atmospheric pressure microwave plasma jet device, in which the pulse power rise rate of the pulse modulated microwave power supply is as high as 2kW / μs, and the pulse steepness is large. The high pulse steepness is beneficial to increasing the number of high-energy electrons, thereby increasing the concentration of active particles and improving the efficiency of microwave plasma in practical applications.

[0018] 3. The present invention provides a dual-channel atmospheric pressure microwave plasma jet device. The dual-channel coaxial resonator is based on the transmission line theory and the length of the resonant cavity is reasonably designed. Plasma can be generated at the open end under lower incident power input.

[0019] 4. The present invention provides a dual-channel atmospheric pressure microwave plasma jet device, in which the coaxial line is designed as a gas transmission pipeline to effectively separate the mixed gas. By adding external power, a plasma jet with a spatiotemporal distribution can be obtained at the open end, and the spatiotemporal distribution adjustment of different active particles can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the working principle of the device of the present invention.

[0021] Figure 2 It is a schematic diagram of the Ar plasma jet state based on the device of the present invention;

[0022] Figure 3 It is a schematic diagram of the pure Ar / N2 plasma jet state based on the device of the present invention;

[0023] Figure 4 It is a schematic diagram of the He plasma jet state based on the device of the present invention;

[0024] Figure 5 It is a schematic diagram of the pure He / N2 plasma jet state based on the device of the present invention;

[0025] Figure 6 Schematic diagram of the time-varying electron density of the Ar / CF4 plasma jet based on the device of the present invention.

[0026] In the figure: 1. Gas pipeline; 2. Large coaxial cavity; 3. SMA interface; 4. Cavity threaded interface; 5. Small coaxial cavity; 6. Hollow coaxial line; 7. Pulse signal modulator; 8. Directional coupler; 9. Power amplifier; 10. Microwave signal generator; 11. Gas flow meter; 12. Needle valve; 13. Pressure reducing valve; 14. Gas storage bottle. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] See also Figure 1 In an embodiment of the present invention, a dual-channel atmospheric pressure microwave plasma jet device is provided, including a dual-channel coaxial resonator, a pulse modulated microwave power supply and a gas path input; the dual-channel coaxial resonator is composed of a gas pipeline 1, a large coaxial cavity 2 and a small coaxial cavity 5, an SMA interface 3, a cavity threaded interface 4, and a hollow coaxial line 6; the large coaxial cavity 2 and the small coaxial cavity 5 are combined into a complete resonant cavity through the cavity threaded interface 4, and the hollow coaxial line 6 is fixed on the resonator. The gas pipeline 1 is made of plastic material, and the inner diameter of the gas inlet end is 4 mm and the outer diameter is 6 mm. It is fixed on the large coaxial cavity 2 by gluing, and the working gas is supplied by the gas pipeline. Channel 1 passes through the resonator and the hollow coaxial line 6, the hollow coaxial line 6 is made of copper, and its inner diameter and outer diameter are 1mm and 2mm respectively; the SMA interface 3 is used for feeding microwave power and generating field strength at the open end; the large coaxial cavity 2 and the small coaxial cavity 5 are made of copper, the outer diameter of the large coaxial cavity 2 is 24mm, the inner diameter is 14mm, and the length is 20mm, the outer diameter of the small coaxial cavity 5 is 10mm, the inner diameter is 8mm, and the length is 30mm, and the outer diameter of the small coaxial cavity at the threaded interface is 14mm. The resonator composed of the large coaxial cavity 2 and the small coaxial cavity 5 is set to be short-circuited at one end and open-circuited at the other end, so as to obtain the maximum field strength at the open end after microwave feeding.

[0029] The pulse modulated microwave power supply includes a pulse signal modulator 7, a microwave signal generator 10, a power amplifier 9 and a directional coupler 8, wherein the microwave energy is generated by the microwave signal generator 10, and the microwave parameters are manually adjusted by the pulse signal modulator 7. The microwave energy generated by the microwave signal generator 10 is transmitted to the SMA interface 3 via the power amplifier 9 and the directional coupler 8, and the SMA interface 3 is 3 mm away from the short-circuit end; the pulse signal modulator 7 outputs a 5V square wave, a duty cycle of 0.01-0.99, and a pulse frequency of 10Hz-200kHz; the frequency range of the microwave signal generator 10 is 2.4GHz-2.5GHz, and the output power is 1mW; the output continuous power of the power amplifier 9 is 0-200W, and the pulse rise rate is 2kW / μs.

[0030] The gas circuit input includes two gas storage bottles 14, two pressure reducing valves 13, two needle valves 12 and a gas flow meter 11. The needle valve 11 and the gas flow meter 12 are used to control the input flow of the working gas.

[0031] In order to further better explain the present invention, the following specific embodiments are also provided:

[0032] Embodiment 1:

[0033] The dual-channel atmospheric pressure microwave plasma jet device of the present invention was built for experimental testing: the pulse modulation microwave power supply parameters were set to: microwave frequency 2.45 GHz, pulse modulation frequency 20 kHz, pulse modulation duty cycle 50%; first, Ar was used as the working gas and passed into the hollow coaxial line 6, and its flow rate was set to 0.3 L / min. The discharge morphology was as follows Figure 2 Then use Ar / N2 as the working gas, where Ar is passed into the hollow coaxial line 6, the flow rate is set to 0.3L / min, N2 is passed into the resonant cavity, the flow rate is set to 2L / min, the discharge morphology is as shown Figure 3 As shown, from Figure 2 to Figure 3 It can be seen that the plasma jet generated by the device of the present invention achieves spatial distribution regulation.

[0034] Embodiment 2:

[0035] The dual-channel atmospheric pressure microwave plasma jet device of the present invention was built for experimental testing: the pulse modulation microwave power supply parameters were set to: microwave frequency 2.45 GHz, pulse modulation frequency 20 kHz, pulse modulation duty cycle 50%. First, He was used as the working gas and introduced into the gas pipeline 1 of the hollow coaxial line 6 at a flow rate of 0.3 L / min. The discharge morphology was as follows: Figure 4Then He / N2 is used as the working gas, He is introduced into the hollow coaxial line 6, and N2 is introduced into the resonator. The flow rates of the two working gases are 0.3L / min and 2L / min, respectively. The discharge morphology is as shown Figure 5 As shown, from Figure 4 to Figure 5 It can be seen that the He and He / N2 jet morphologies show elongated stratified shapes, and different plasmas appear in different spatial positions of the jets.

[0036] Embodiment three:

[0037] The plasma jet based on the device of the present invention was diagnosed with time-varying electron density. The discharge parameters were set as follows: microwave frequency 2.45 GHz, pulse modulation frequency 20 kHz, pulse modulation duty cycle 50%. 0.5 L / min of Ar was introduced into the hollow coaxial line 6, and 0.6 L / min of CF4 gas was introduced into the resonant cavity. The time-varying electron density of the plasma jet under these parameters was measured using a microwave Rayleigh scattering device. The results are as follows: Figure 6 As shown. Figure 6 It can be seen from the figure that the electron density of the microwave plasma jet under the device of the present invention can reach 10 20 Order of magnitude.

[0038] In summary: the dual-channel atmospheric pressure microwave plasma jet device provided by the present invention can not only separate the working gas, but also realize the spatiotemporal distribution regulation of active particles in the plasma jet, and the density of active particles generated is large. The temperature of the plasma jet can be effectively adjusted by controlling the pulse modulation parameters, thereby increasing the application range of the microwave plasma jet.

[0039] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A dual-channel atmospheric pressure microwave plasma jet device, characterized in that: The invention comprises a dual-channel coaxial resonator, a pulse modulated microwave power supply and a gas input; the dual-channel coaxial resonator is composed of a gas pipeline (1), a large coaxial cavity (2) and a small coaxial cavity (5), an SMA interface (3), a cavity thread interface (4) and a hollow coaxial line (6); the large coaxial cavity (2) and the small coaxial cavity (5) are combined into a complete resonant cavity through the cavity thread interface (4); the hollow coaxial line (6) is fixed on the resonator, and the working gas is passed into the resonator and the hollow coaxial line (6) through the gas pipeline (1); the SMA interface (3) is used for feeding in microwave power and generating a field strength at the open end; The microwave energy of the pulse modulated microwave power source is generated by a microwave signal generator (10), and its microwave parameters are manually adjusted by a pulse signal modulator (7). The microwave energy generated by the microwave signal generator (10) is transmitted to the SMA interface (3) via a power amplifier (9) and a directional coupler (8); The gas circuit input comprises a gas storage bottle (14), a pressure reducing valve (13), a needle valve (12) and a gas flow meter (11), and the needle valve (12) and the gas flow meter (11) are used to control the input flow rate of the working gas.

2. A dual-channel atmospheric pressure microwave plasma jet device according to claim 1, characterized in that: The large coaxial cavity (2) and the small coaxial cavity (5) are made of copper. The large coaxial cavity (2) has an outer diameter of 24 mm, an inner diameter of 14 mm and a length of 20 mm. The small coaxial cavity (5) has an outer diameter of 10 mm, an inner diameter of 8 mm and a length of 30 mm. The outer diameter of the threaded interface of the small coaxial cavity is 14 mm.

3. A dual-channel atmospheric pressure microwave plasma jet device as claimed in claim 2, characterized in that: The resonator composed of the large coaxial cavity (2) and the small coaxial cavity (5) is arranged with one end short-circuited and the other end open-circuited, so as to obtain the maximum field strength at the open end after microwave feeding.

4. A dual-channel atmospheric pressure microwave plasma jet device as claimed in claim 1, characterized in that: The hollow coaxial line (6) is made of copper, and its inner diameter and outer diameter are 1 mm and 2 mm respectively.

5. A dual-channel atmospheric pressure microwave plasma jet device according to claim 1, characterized in that: The SMA interface (3) is 3 mm away from the short-circuit end.

6. A dual-channel atmospheric pressure microwave plasma jet device according to claim 1, characterized in that: The gas pipeline (1) is made of plastic material, has an inner diameter of 4 mm and an outer diameter of 6 mm at its gas inlet end, and is fixed to the large coaxial cavity (2) by gluing.

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