CN119136397A

CN119136397A - A microwave cold plasma generating device based on a coaxial arrowhead-shaped structure

Info

Publication number: CN119136397A
Application number: CN202411290550.1A
Authority: CN
Inventors: 黄劢韦
Original assignee: Chengdu Haoyun Haomai Technology Co ltd
Current assignee: Chengdu Haoyun Haomai Technology Co ltd
Priority date: 2024-09-14
Filing date: 2024-09-14
Publication date: 2024-12-13

Abstract

The invention discloses a microwave cold plasma generating device based on a coaxial arrowhead-shaped structure, which relates to the field of plasma generating devices, including an outer conductor sleeve, the interior of which includes a cylindrical cavity and a conical cavity that are connected, and the interior of the outer conductor sleeve can be connected to a gas source; an inner conductor, which is arranged in the outer conductor sleeve and coaxially arranged with the outer conductor sleeve, and the inner conductor is used to transmit microwave energy to the conical cavity area; the inner conductor includes a columnar portion and an arrowhead portion, one end of the columnar portion is connected to the microwave source, and the other end is connected to the opposite side of the tip of the arrowhead portion, and the columnar portion is used to transmit the microwave energy of the microwave source to the arrowhead portion. The invention sets the tip of the arrowhead portion to be lower than the tip of the conical cavity, forms a conical cavity at the coaxial terminal, and adopts a unique arrowhead-shaped inner conductor structure, which does not block the internal gas circulation while improving the electric field strength of the coaxial terminal, so as to facilitate the low-power self-excited working gas to generate plasma.

Description

Microwave cold plasma generating device based on coaxial metal arrowhead type structure

Technical Field

The invention relates to the field of plasma generating devices, in particular to a coaxial metal arrowhead-type structure-based microwave cold plasma generating device.

Background

The plasma is composed of electrons, ions, radicals, photons, and other neutral particles. Wherein electrons, ions and radicals are active particles, which react very easily with the surface of other solid substances, and plasma treatment is performed by utilizing this characteristic. Plasma is considered as a fourth form of matter present in addition to solid, liquid, and gas. The excitation of the plasma state needs to meet certain conditions, such as a certain low pressure (vacuum), a certain electric field or temperature, etc. The plasma can be classified into high temperature plasma and low temperature plasma according to temperature classification. The temperature of the high-temperature plasma can be from one hundred degrees to ten thousand degrees, the temperature of the plasma jet is high, and the surface temperature is higher after the plasma jet collides with a solid phase, so that the plasma is only suitable for treating heat-resistant materials such as ceramics, metals and the like. The temperature of the low-temperature plasma can be controlled to be close to normal temperature, and the low-temperature plasma is suitable for treating thermolabile materials such as plastics, silica gel, chips and the like.

The microwave is one of the methods for generating the plasma, and compared with other traditional plasmas, the microwave plasma has the advantages of low substrate temperature, stable and easy control of a microwave generator, high efficiency of microwave discharge, high safety factor, quiet plasma and the like, and a plasma generation chamber and a treatment chamber can be separated and combined, so that the process is flexible. The atmospheric pressure microwave plasma jet has the advantages of moderate gas temperature, stable system, lower cost and the like. The method is widely applied to various fields such as material surface cleaning and etching, sewage treatment, polymer material surface modification, wound disinfection, cancer cell treatment and the like. Wherein the active radicals and energetic particles of the plasma jet can significantly affect the effectiveness of the application. At present, there is little progress in the research of microwave plasma technology in China, but there is little distance from commercialization.

Atmospheric pressure microwave plasma jet has been studied to some extent, for example, in the prior art, an atmospheric pressure microwave plasma device mainly includes two structures, the first is a rectangular waveguide structure, and the structure mostly adopts a rectangular waveguide as a plasma excitation area. The microwave plasma torch structure has the advantages of focusing electric field, realizing that microwave energy is gathered in a region to be excited to generate a larger electric field through a compressed waveguide, and carrying out tip discharge by a high-voltage probe, and the plasma and the cylindrical resonant cavity form a coaxial structure, continuously introducing gas, on one hand, maintaining the gas component of the plasma, on the other hand, driving the plasma to flow out directionally, and simultaneously taking away a large amount of heat by the gas, thereby playing a role in heat dissipation.

However, in the two structures, the problems of self-ignition, plasma maintenance and safety are that higher microwave power is needed to excite and form plasma, the energy conversion efficiency of the plasma is not high, the normal pressure plasma torch is unstable, the plasma is difficult to maintain even under severe conditions, the synthetic material impurities are more, particularly, metal wires are needed to be ignited during ignition, pollutants are easy to introduce, meanwhile, the plasma contains a large amount of free electrons, so that the conductivity of the plasma is extremely strong, after the plasma generator generates the plasma, the high-density cylindrical plasma is used as an electromagnetic energy conducting medium and is equivalent to an antenna, electromagnetic waves are radiated outwards, the microwave radiation is not controlled in the prior art, and the long-term use is unsafe.

Disclosure of Invention

The invention aims to provide a coaxial metal arrowhead-type structure-based microwave cold plasma generating device, which is combined with an inner conductor with an arrow head part through an outer conductor sleeve with a conical cavity, so as to solve the problems that the self-ignition is difficult to realize and the low-temperature plasma is difficult to prepare in the prior art.

The embodiment of the invention is realized by the following technical scheme:

The embodiment of the invention provides a coaxial metal arrowhead-type structure-based microwave cold plasma generating device, which comprises:

The outer conductor sleeve is arranged as a peripheral structure of the plasma generation area, the inside of the outer conductor sleeve comprises a cylindrical cavity and a conical cavity which are communicated, and the inside of the outer conductor sleeve can be communicated with an air source;

the inner conductor is arranged in the outer conductor sleeve and is coaxially arranged with the outer conductor sleeve, an annular gap is formed between the inner conductor and the outer conductor sleeve, and the inner conductor is used for transmitting microwave energy to the conical cavity area;

The inner conductor comprises a columnar part and an arrow part, one end of the columnar part is connected with the microwave source, the other end of the columnar part is connected with the opposite side of the tip of the arrow part, and the columnar part is used for transmitting microwave energy of the microwave source to the arrow part;

the columnar part is positioned in the columnar cavity, and the arrow head is positioned in the conical cavity;

The tip of the arrow part is arranged at the tip side of the conical cavity, the outer conductor sleeve at the tip side of the conical cavity is provided with a transmitting hole, the tip end face of the arrow part is lower than the end face of the transmitting hole, and the transmitting hole is used for transmitting cold plasma to the external environment of the outer conductor sleeve;

The conical cavity is arranged to concentrate an electric field in microwave energy at the tip of the arrow part, so that the electric field intensity at the tip of the arrow part is increased, and the self-ignition excitation gas source is realized to generate plasma.

Further, the outer conductor sleeve comprises a cylindrical sleeve and a conical sleeve, the cylindrical cavity is positioned in the cylindrical sleeve, the conical cavity is positioned in the conical sleeve, and the top of the cylindrical sleeve is detachably connected with the bottom of the conical sleeve;

The diameter of the cylindrical cavity is equal to the maximum diameter of the conical cavity.

Further, a limiting mechanism is arranged in the outer conductor sleeve, and the limiting mechanism is arranged to coaxially limit the inner conductor and the outer conductor sleeve.

Further, an annular groove is formed in the cylindrical sleeve, the limiting mechanism is a limiting gasket, the limiting gasket is arranged in the annular groove, and the limiting gasket and the outer conductor sleeve are coaxially arranged;

The center of the limiting gasket is provided with a through hole, the columnar part penetrates through the through hole, the arrow part is positioned above the limiting gasket, the limiting gasket is provided with a plurality of vent holes, and the vent holes are used for circulating an air source in a cavity below the limiting gasket to the cavity above the limiting gasket.

Further, the columnar part comprises a lower external connection part and an upper internal connection part which are axially connected, the lower external connection part is connected with a microwave source connection mechanism, and the diameter of the through hole is larger than that of the upper internal connection part and smaller than the outer diameter of the lower external connection part;

the arrow part comprises a tip part and a connecting part which are axially connected, the connecting part is of a hollow structure with a downward opening, and the upper inscription part of the columnar part can be inserted into the hollow structure;

The upper inscription part is inserted into the hollow structure after penetrating through the through hole, and the limit gasket is fixed at the joint of the columnar part and the arrow part;

the outer diameter of the connecting part is larger than the diameter of the through hole.

Further, when the limit gasket is fixed at the joint of the columnar part and the arrow part, the upper end face of the lower external connection part is attached to the bottom of the limit gasket, and the lower end face of the connecting part is attached to the upper end of the limit gasket;

the upper internal joint is in threaded connection with the connecting part.

Further, the microwave source connecting mechanism comprises a first connecting end and a second connecting end, a mounting plate is arranged between the first connecting end and the second connecting end, and the mounting plate is fixedly connected with the bottom of the cylindrical sleeve through a plurality of bolt mechanisms;

the first connecting end penetrates through the bottom of the cylindrical sleeve and is connected with the lower external connection part of the cylindrical part, the mounting plate and the second connecting end are arranged on the outer side of the cylindrical sleeve, and the second connecting end is used for connecting a microwave source.

Further, the bottom of the cylindrical sleeve is provided with an air inlet component which is communicated with the cylindrical cavity, and the air inlet component is arranged to be communicated with an air source pipeline at the outer side of the air inlet component and convey an air source in the air source pipeline into the cylindrical cavity;

the flow direction of the air source conveyed by the air inlet assembly, which enters the cylindrical cavity for the first time, is the horizontal direction.

Further, a blocking mechanism is arranged above the outer conductor sleeve, and is arranged at the emitting hole to prevent microwaves from passing through and allow gas to circulate, so that microwave energy is prevented from leaking after plasma is excited.

Further, the separation mechanism comprises four separation blocks, gaps exist between two adjacent separation blocks, the four separation blocks enclose into a cone structure, the diameter of the cone structure gradually decreases from bottom to top, the cone structure is provided with a central channel, the central channel is communicated with an emitting hole and an external environment, and the central channel and the emitting hole are coaxially arranged.

Compared with the prior art, the embodiment of the invention has the following advantages and beneficial effects:

1. the outer conductor sleeve is of a peripheral structure of a plasma generation area, a cylindrical cavity and a conical cavity are arranged in the outer conductor sleeve and are used for connecting an air source, an annular gap formed between the inner conductor and the outer conductor sleeve is a key area for converting microwave energy into an electric field, and the inner conductor is responsible for transmitting the microwave energy from the microwave source to the conical cavity area.

When microwaves propagate in the cylindrical cavity and the conical cavity, the microwaves form standing waves in the cavity due to the size and shape of the cavity, and the anti-nodes of the standing waves are positioned at the tip of the conical cavity, so that plasma is generated. The columnar portion is positioned within the columnar cavity to transfer energy from the microwave source to the arrow-head portion, the columnar portion helping to maintain efficient transfer of microwave energy and ensuring that the energy does not decay too much before reaching the arrow-head portion. The arrowhead is located within the conical cavity, the tip of which is the critical area for plasma generation, and the arrowhead concentrates the electric field at the tip, thereby creating a high electric field strength in that area, facilitating breakdown of the gas and formation of the plasma.

The arrangement position of the arrow part corresponds to the conical cavity, namely the tip side of the conical cavity corresponds to the tip side of the arrow part, so that effective transmission and concentration of electric field energy are ensured, plasma generation can be realized under lower microwave power, self-ignition excitation of the air source to generate plasma is realized, and energy efficiency is improved.

Meanwhile, the structure of the conical cavity is beneficial to controlling the shape and jet length of the plasma, so that the plasma is more uniform and stable. In addition, since the arrow tip is lower than the end face of the emission hole, it helps to prevent the plasma from directly contacting some parts of the device, thereby protecting the device and ensuring stable generation of plasma.

2. The outer conductor sleeve comprises a cylindrical sleeve and a conical sleeve, wherein a cylindrical cavity is formed in the cylindrical sleeve and used for accommodating a cylindrical part of an inner conductor and providing a channel for microwave energy transmission, and the conical cavity is formed in the conical sleeve and is beneficial to focusing of an electric field, particularly to the vicinity of the pointed end of an arrow and excitation of plasma.

3. The limiting mechanism provided by the embodiment of the invention ensures the stability of the coaxial positions of the inner conductor and the outer conductor sleeve, can be a limiting gasket, is matched with the annular groove of the cylindrical sleeve to realize detachable stable connection, and is provided with a plurality of vent holes, so that the correct position and the coaxiality of the inner conductor are ensured, and the circulation of gas in the annular gap is not influenced.

4. The embodiment of the invention is provided with the baffle at the transmitting hole, which is equivalent to a cut-off waveguide, and utilizes the principle of the cut-off frequency of electromagnetic waves in the waveguide, and the electromagnetic waves can not propagate in the waveguide below the cut-off frequency, so that the cut-off of the microwaves can be realized. In a plasma generating apparatus, the apparatus can effectively prevent leakage of microwave energy even after plasma excitation, thereby improving operational safety.

5. The air source in the embodiment of the invention enters the plasma generating device from the single air inlet component and is similar to the input end of the microwave source connecting mechanism. When in actual use, the gas pipeline and the cable of the microwave source can be bundled together to form a traction wire, and the pipeline or the cable is not bent when being arranged on the same side.

In general, the embodiment of the invention provides a microwave cold plasma generating device based on a coaxial metal arrowhead type structure, which combines an outer conductor sleeve with a conical cavity and an inner conductor with an arrow part, sets the tip of the arrow part to be lower than the tip of the conical cavity, adopts a unique metal arrowhead type inner conductor structure while forming the conical cavity at a coaxial terminal, does not block the internal gas circulation, improves the electric field strength of the coaxial terminal, and is convenient for low-power self-excited working gas to generate plasma.

Drawings

In order to more clearly illustrate the technical solutions of the present application, the drawings that are needed in the description of the present application will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.

FIG. 1 is a schematic diagram of an explosion structure of a microwave cold plasma generating device according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional structure of a microwave cold plasma generating device according to an embodiment of the present invention;

fig. 3 is a schematic diagram of the overall structure of a microwave cold plasma generating device according to an embodiment of the present invention;

FIG. 4 is a block diagram showing the internal structure of a microwave cold plasma generator according to an embodiment of the present invention;

FIG. 5 is a diagram showing the relationship between an inner conductor, a spacing pad and a microwave source connection mechanism according to an embodiment of the present invention;

FIG. 6 is a diagram showing the relationship between a cylindrical sleeve and an inner conductor and microwave source connection mechanism according to an embodiment of the present invention;

fig. 7 is a schematic diagram showing an electric field distribution of a microwave plasma torch provided by an embodiment of the present invention outside a cylindrical cavity and a conical cavity;

FIG. 8 is a schematic diagram of the distribution of the electric field of a microwave plasma torch within a cylindrical cavity and a conical cavity according to an embodiment of the present invention;

Fig. 9 is a front view of a partial enlarged distribution of an electric field of a microwave plasma torch at a tip portion according to an embodiment of the present invention;

Fig. 10 is a top view of a partial enlarged distribution of an electric field of a microwave plasma torch at a tip portion according to an embodiment of the present invention.

Reference numerals illustrate:

100. The device comprises an outer conductor sleeve, 101, a cylindrical cavity, 102, a conical cavity, 103, a transmitting hole, 104, a cylindrical sleeve, 105, a conical sleeve, 106, an annular groove, 200, an inner conductor, 201, a cylindrical part, 202, an arrow part, 203, a lower external part, 204, an upper internal part, 205, a tip part, 206, a connecting part, 300, a limiting mechanism, 301, a limiting gasket, 302, a through hole, 303, a vent hole, 400, a microwave source connecting mechanism, 401, a first connecting end, 402, a second connecting end, 403, a mounting plate, 404, a bolt mechanism, 500, an air inlet component, 501, a connecting pipe, 502, a mounting hole, 600, a blocking mechanism, 601, a blocking block, 602 and a central channel.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Example 1:

Fig. 1 to 4 show, wherein fig. 1 is an explosion structure schematic diagram of a microwave cold plasma generating device, fig. 2 is a cross-sectional structure schematic diagram of the microwave cold plasma generating device, fig. 3 is an overall structure schematic diagram of the microwave cold plasma generating device, and fig. 4 is a line block diagram of an internal structure of the microwave cold plasma generating device. A coaxial metal arrowhead-type structure microwave cold plasma generating device, comprising:

an outer conductor sleeve 100, which is arranged as a peripheral structure of a plasma generation area, wherein the inside of the outer conductor sleeve 100 comprises a cylindrical cavity 101 and a conical cavity 102 which are communicated, and the inside of the outer conductor sleeve 100 can be communicated with an air source;

An inner conductor 200, preferably made of brass, disposed within the outer conductor sleeve 100 and coaxially disposed with the outer conductor sleeve 100, with an annular gap formed between the inner conductor 200 and the outer conductor sleeve 100, the inner conductor 200 being configured to transmit microwave energy to the region of the tapered cavity 102;

Wherein the inner conductor 200 comprises a columnar portion 201 and an arrow portion 202, one end of the columnar portion 201 is connected with the microwave source, and the other end is connected with the opposite side of the tip of the arrow portion 202, and the columnar portion 201 is used for transmitting microwave energy of the microwave source to the arrow portion 202;

The columnar part 201 is positioned in the columnar cavity 101, and the arrow part 202 is positioned in the conical cavity 102;

The tip of the arrow part 202 is arranged on the tip side of the conical cavity 102, the outer conductor sleeve 100 on the tip side of the conical cavity 102 is provided with a transmitting hole 103, the tip end face of the arrow part 202 is lower than the end face of the transmitting hole 103, and the transmitting hole 103 is used for transmitting cold plasma to the external environment of the outer conductor sleeve 100;

The tapered cavity 102 is configured to focus the electric field in the microwave energy at the tip of the arrow head 202, increasing the electric field strength at the tip of the arrow head 202, enabling the self-igniting excited gas source to generate a plasma.

Specifically, the device provided by the embodiment of the invention adopts a coaxial structure, that is, the inner conductor 200 is positioned on the central axis of the outer conductor sleeve 100, so that the efficiency of concentrating and transmitting microwave energy can be ensured, one end of the columnar part 201 of the inner conductor 200 is connected with the microwave source, the other end of the columnar part is connected with the arrow part 202, the energy of the microwave source is transmitted to the arrow part 202, the conical cavity 102 is arranged without blocking the circulation of internal gas, and at the same time, the electric field in the microwave energy is focused at the tip of the arrow part 202, and high electric field strength is generated at the point, which is sufficient for ionizing gas source molecules to generate plasma, that is, self-ignition is realized.

Wherein the columnar portion 201 of the inner conductor 200 is directly connected to a microwave source, ensuring efficient transmission of energy. The connection of the pillar portion 201 to the arrow portion 202 ensures that energy is transferred from the pillar portion 201 to the arrow portion 202, the arrangement of the arrow portion 202 facilitating focusing of the electric field. The outer conductor sleeve 100 is provided in communication with the interior thereof and is capable of being connected to a gas source to provide the necessary gas for generating plasma. The tip of the arrow 202 is located below the emission hole 103, ensuring that the plasma can be guided to the external environment through the emission hole 103.

Because the electric field intensity of the tip of the arrow part 202 is high, plasma can be generated under lower microwave energy input, the tip of the arrow part 202 is positioned below the emitting hole 103, so that the energy consumption and loss can be reduced, the energy efficiency of the whole system can be improved, meanwhile, the plasma can be prevented from directly impacting the end face of the emitting hole 103, and the erosion and damage to device materials can be reduced, so that the service life of equipment can be prolonged.

In the operation process, the generation and output of the plasma can be controlled by adjusting the power of the microwave source and the flow of the air source, and the coaxial structure enables the device to be small in size and convenient to integrate into various devices.

The embodiment of the invention fully utilizes the principles of microwave energy and electric field focusing, and utilizes the special shape of the conical cavity 102 to enhance the electric field strength, so that the microwave energy is concentrated in the conical cavity 102 while the internal gas circulation is not blocked. Particularly at the tip of the arrow portion 202, the electric field lines are more concentrated due to the tip effect, and the electric field strength is significantly increased. The electric field distribution facilitates easier ionization of gas molecules at the tip of the arrow 202, and plasma can be generated at lower microwave power due to concentration of the electric field. Wherein the cylindrical cavity 101 provides a stable environment such that the inner conductor 200 can transmit the energy of the microwave source to the area of the conical cavity 102, uniformly distributing the microwave energy within the cylindrical cavity 101, and then concentrating the energy at the tip of the arrow portion 202 by the focusing action of the conical cavity 102. Therefore, the plasma is generated by self-ignition excitation, and the generated cold plasma can be used in various application fields such as surface treatment, disinfection, material processing and the like.

Further, the outer conductor sleeve 100 comprises a cylindrical sleeve 104 and a conical sleeve 105, the cylindrical sleeve 104 and the conical sleeve 105 are preferably made of brass, the cylindrical cavity 101 is positioned in the cylindrical sleeve 104, the conical cavity 102 is positioned in the conical sleeve 105, the top of the cylindrical sleeve 104 is detachably connected with the bottom of the conical sleeve 105, and the diameter of the cylindrical cavity 101 is equal to the maximum diameter of the conical cavity 102.

It should be noted that, the cylindrical sleeve 104 and the conical sleeve 105 may be integrally disposed, or may be disposed in a spliced manner, which is not limited herein.

As the preferred embodiment of the invention, the cylindrical sleeve 104 and the conical sleeve 105 are connected through the threaded structure, and the connecting structure not only can ensure enough connection stability and tightness, but also provides a flexible detachable connecting structure, is convenient for cleaning the whole cavity and maintaining and replacing single parts, and improves the use flexibility of the whole device.

Of course, in other embodiments, the connection manner of the cylindrical sleeve 104 and the conical sleeve 105 is not limited to the threaded connection, and may be an adhesive connection, a clamping connection, a welding connection, or the like, so long as the effect of sufficient connection stability and sealing performance can be achieved.

Returning to the embodiment of the invention, cylindrical sleeve 104 provides cylindrical cavity 101 and conical sleeve 105 provides conical cavity 102. The outer shapes of the cylindrical sleeve 104 and the tapered sleeve 105 are not limited herein, and may be set according to actual needs as long as the purpose of providing the cylindrical cavity 101 and the tapered cavity 102, respectively, can be achieved.

As a preferred embodiment of the present invention, the outer shape of both the cylindrical sleeve 104 and the conical sleeve 105 are provided as cylindrical shapes. The arrangement of the cylindrical cavity 101 with the diameter equal to the maximum diameter of the conical cavity 102 in the embodiment of the invention helps to smoothly transition energy, reduce the loss of energy in the propagation process, and also helps to maintain the stability of plasma.

In order to improve stability of the relative position between the outer conductor sleeve 100 and the inner conductor 200, a limiting mechanism 300 may be provided in the outer conductor sleeve 100, and the limiting mechanism 300 may be configured to coaxially limit the inner conductor 200 and the outer conductor sleeve 100. The application of the coaxial confinement technique ensures proper centering of the inner conductor 200 within the cylindrical cavity 101, prevents misalignment, and achieves efficient transmission of microwave energy in the annular gap and uniformity of the plasma.

In particular, the stop mechanism 300 may be implemented mechanically, such as using stop bolts, retainers, or specially designed components to limit movement of the inner conductor 200, ensuring that it remains in the correct position during assembly and operation.

Importantly, the spacing mechanism 300 requires consideration in the process of setting up that the spacing mechanism 300 does not affect the delivery and flow of gas. Illustratively, an annular groove 106 is arranged in the cylindrical sleeve 104, the limiting mechanism 300 is a limiting gasket 301, the limiting gasket 301 is arranged in the annular groove 106, the limiting gasket 301 and the outer conductor sleeve 100 are coaxially arranged, a through hole 302 is arranged in the center of the limiting gasket 301, the cylindrical part 201 penetrates through the through hole 302, the arrow part 202 is located above the limiting gasket 301, a plurality of ventilation holes 303 are arranged on the limiting gasket 301, and the ventilation holes 303 are used for circulating an air source in a cavity below the limiting gasket 301 into a cavity above the limiting gasket 301.

Specifically, annular groove 106 is located inside cylindrical sleeve 104 for mounting limit pad 301, limiting the position and angle of mounting limit pad 301 within outer conductor sleeve 100. The limiting spacer 301 is preferably horizontally mounted, and a through hole 302 is formed in the center of the limiting spacer 301 for penetrating the columnar portion 201 of the inner conductor 200, and the through hole 302 has a limiting effect on the inner conductor 200.

Preferably, inner conductor 200 is disposed perpendicular to spacing pad 301.

Wherein, a plurality of vent holes 303 are arranged on the limiting gasket 301, the limiting gasket 301 coaxially limits the inner conductor 200 through the central hole, ensures the correct position of the inner conductor 200 in the cylindrical sleeve 104, and ensures the gas circulation through the vent holes 303 on the limiting gasket 301.

It should be noted that the material of the limiting gasket 301 is not limited herein, and the material of the limiting gasket 301 should be selected in consideration of various aspects such as temperature resistance, chemical resistance, mechanical strength, creep resistance, processability, compatibility with a medium in contact, and cost effectiveness, preferably, polytetrafluoroethylene is a polytetrafluoroethylene material, and the polytetrafluoroethylene has strong chemical stability, and is an insulating material, so that the electric field in the outer conductor sleeve 100 is not affected, and the polytetrafluoroethylene does not react chemically with plasma or gas.

It should be noted that the size, number and arrangement of the through holes 302 on the limiting gasket 301 are not limited herein, so long as the sufficient supporting performance of the limiting gasket 301 and the smoothness of the air flow in the cavity can be ensured.

As a preferred embodiment of the present invention, the through holes 302 on the limiting gasket 301 are uniformly distributed, and may be arranged in a circular array, for example. The uniform distribution of the through holes 302 facilitates the gas source to form a uniform gas flow between the cavities below and above the spacing pad 301, which facilitates the uniform generation and maintenance of the plasma.

For example, six through holes 302 are uniformly distributed on the limiting gasket 301, and are distributed in a circular array. Of course, in other embodiments, the number of the through holes 302 may be two, three, four, etc., and the arrangement is not limited to a circular array.

Example 2:

the difference from embodiment 1 is that the specific structure of the inner conductor 200 is set in detail.

Illustratively, as shown in fig. 5, the columnar portion 201 includes a lower external connection portion 203 and an upper internal connection portion 204 which are axially connected, the lower external connection portion 203 is connected with a microwave source connection mechanism 400, the diameter of the through hole 302 is larger than the diameter of the upper internal connection portion 204 and smaller than the outer diameter of the lower external connection portion 203, the arrow portion 202 includes a tip portion 205 and a connection portion 206 which are axially connected, the connection portion 206 is a hollow structure with a downward opening, the upper internal connection portion 204 of the columnar portion 201 can be inserted into the hollow structure, the upper internal connection portion 204 is arranged to penetrate through the through hole 302 and then be inserted into the hollow structure, and the limit gasket 301 is fixed at the connection portion of the columnar portion 201 and the arrow portion 202, and the outer diameter of the connection portion 206 is larger than the diameter of the through hole 302.

Specifically, the lower external connection portion 203 is a lower end portion of the pillar portion 201, and is connected to the microwave source connection mechanism 400, so as to receive energy transmitted from the microwave source, and the upper internal connection portion 204 is an upper end portion of the pillar portion 201, and is configured to be inserted into a hollow structure of the arrow portion 202, so as to connect the pillar portion 201 and the arrow portion 202. The through hole 302 is disposed at the center of the limit gasket 301, and is used for the upper inscription part 204 of the columnar part 201 to pass through, so as to realize preliminary limit of the limit gasket 301 and the columnar part 201.

The diameter of the through hole 302 is set to be larger than the diameter of the upper inner joint 204, so that the upper inner joint 204 can be ensured to pass through smoothly, and is smaller than the outer diameter of the lower outer joint 203, so as to ensure good sealing and fixing between the lower outer joint 203 and the limiting gasket 301.

Wherein, the tip 205 is the front section of the arrow 202, is located in the conical cavity 102, and is responsible for generating high electric field intensity at the tip, and exciting the gas source to generate plasma. The connecting portion 206 is a rear section of the arrow portion 202, is hollow, and is designed to be opened downward so that the upper inscription portion 204 of the pillar portion 201 can be inserted therein to achieve connection. The outer diameter of the connection portion 206 is set to be larger than the diameter of the through hole 302, and when the upper inner joint portion 204 passes through the through hole 302 and is inserted into the hollow structure of the connection portion 206, the limit pad 301 can be fixed at the connection portion of the pillar portion 201 and the arrow portion 202, ensuring the stability and coaxiality of the entire inner conductor 200.

The above-mentioned connection structure ensures tight connection between the columnar portion 201 and the arrow-shaped portion 202 of the inner conductor 200, and simultaneously fixes the limit gasket 301 by using the through holes 302 on the limit gasket 301 and the hollow structure of the connection portion 206, thereby ensuring stability and coaxiality of the whole inner conductor 200, being beneficial to improving efficiency of microwave energy transmission and uniformity of plasma generation, and being convenient for assembly and maintenance.

In a preferred embodiment of the present invention, when the limit gasket 301 is fixed at the connection position between the pillar portion 201 and the arrow portion 202, the upper end surface of the lower external portion 203 is attached to the bottom of the limit gasket 301, the lower end surface of the connecting portion 206 is attached to the upper end of the limit gasket 301, and the upper internal portion 204 is screwed to the connecting portion 206. In this preferred structure, the spacer 301 not only functions to fix the inner conductor 200, but also ensures accurate alignment and coaxiality between the columnar portion 201 and the arrow-head portion 202.

Specifically, this structure helps to ensure the sealability and structural stability between the columnar portion 201 and the stopper spacer 301, and at the same time, the lower end face of the connecting portion 206 of the arrow portion 202 is also closely fitted to the upper end of the stopper spacer 301, and alignment and fixation between the arrow portion 202 and the stopper spacer 301 are also further ensured. The upper inner joint part 204 of the columnar part 201 and the connecting part 206 of the arrow part 202 are connected by screw threads, which allow fine adjustment during assembly to ensure accurate coaxiality and correct position of the inner conductor 200, and the screw thread connection structure provides good mechanical strength to ensure that the connection between the columnar part 201 and the arrow part 202 is not loosened due to vibration or thermal expansion during operation of the plasma generating device.

Example 3:

The difference from embodiment 2 is that the microwave source connection mechanism 400 is specifically provided.

As shown in fig. 5 and 6, the microwave source connection mechanism 400 includes a first connection end 401 and a second connection end 402, a mounting plate 403 is disposed between the first connection end 401 and the second connection end 402, the mounting plate 403 is fixedly connected to the bottom of the cylindrical sleeve 104 through a plurality of bolt mechanisms 404, the first connection end 401 penetrates through the bottom of the cylindrical sleeve 104 and is connected to the lower external connection portion 203 of the cylindrical portion 201, the mounting plate 403 and the second connection end 402 are disposed outside the cylindrical sleeve 104, and the second connection end 402 is used for connecting a microwave source.

Specifically, the first connection end 401 is a part of the microwave source connection mechanism 400, and is connected to the lower external connection portion 203 of the columnar portion 201 of the inner conductor 200, preferably in a threaded connection manner, so that good electromagnetic compatibility and sealing performance are ensured to prevent loss of microwave energy. The second connection end 402 is another part of the connection mechanism, and is located on the outer side of the cylindrical sleeve 104, for connecting to an external microwave source, and the mounting plate 403 is an intermediate structure connecting the first connection end 401 and the second connection end 402, providing a stable platform for mounting and fixing the entire microwave source connection mechanism 400.

It should be noted that, the first connection end 401, the second connection end 402 and the mounting plate 403 may be integrally provided, or may be detachably connected, which is not limited herein, so that the first connection end 401, the second connection end 402 and the mounting plate 403 are integrally provided for easy understanding.

Preferably, the mounting plate 403 is fixedly attached to the bottom of the cylindrical sleeve 104 by a plurality of bolt mechanisms 404 in a manner that not only provides structural stability, but also allows the attachment mechanisms to be disassembled and serviced when needed.

Wherein the first connection end 401 extends through the bottom of the cylindrical sleeve 104 and transmits microwave energy from the connection mechanism directly to the cylindrical portion 201 of the inner conductor 200. The mounting plate 403 and the second connection end 402 are disposed on the outer side of the cylindrical sleeve 104, which helps to protect the microwave source connection mechanism 400 from the direct influence of the plasma generation region, and also facilitates monitoring and maintenance by an operator, and also ensures stability and sealing of the microwave source connection mechanism 400.

In the present embodiment, the number of the bolt mechanisms 404 is not limited here, nor is the shape of the mounting plate 403 limited here, as long as sufficient effects of mounting stability and sealability can be achieved, and the mounting plate is illustratively a rectangular parallelepiped thin plate, and the bolt mechanisms 404 are provided with four, respectively provided on four right-angle sides of the rectangular parallelepiped thin plate.

Further, an air inlet assembly 500 is arranged at the bottom of the cylindrical sleeve 104, the air inlet assembly 500 is communicated with the cylindrical cavity 101, the air inlet assembly 500 is arranged to be communicated with an air source pipeline at the outer side of the air inlet assembly 500, and an air source in the air source pipeline is conveyed into the cylindrical cavity 101. As shown in fig. 4, the direction of flow of the air source delivered through the air intake assembly 500 into the cylindrical cavity 101 for the first time is horizontal.

Specifically, the air inlet assembly 500 is disposed at the bottom of the cylindrical sleeve 104, which is beneficial to the introduction and distribution of the air source, and the air inlet assembly 500 is directly communicated with the cylindrical cavity 101, so as to ensure that the air source can smoothly enter and fill the cavity, and the outer side of the air inlet assembly 500 is communicated with the air source pipeline.

Illustratively, the air source conduit is a connecting tube 501 as shown, and the air source first enters the air intake assembly 500 from the connecting tube 501 and is then delivered into the cylindrical cavity 101, and a mounting hole 502 may be provided in the bottom of the cylindrical sleeve 104 to facilitate connection with the connecting tube 501.

In the embodiment of the present invention, preferably, the flow direction of the gas source fed through the gas inlet assembly 500, which first enters the cylindrical cavity 101, is horizontal, and the gas source forms a uniform gas flow in the cavity, so as to provide uniform gas distribution for plasma generation. Of course, the air inlet assembly 500 may also include a valve or other control mechanism for adjusting the flow rate and pressure of the air source so as to control the characteristics of the plasma, such as density and temperature, and the air inlet assembly 500 may also be provided with a seal ring for ensuring structural tightness, etc., so as to prevent air leakage and ensure safe and effective delivery of the air source.

More optionally, the embodiment of the present invention provides a single air inlet assembly 500 at the bottom of the cylindrical sleeve 104, such that the air source enters the plasma generating device from the single air inlet assembly 500 and is positioned close to the input end of the microwave source connection mechanism 400. When in actual use, the gas pipeline and the cable of the microwave source can be bundled together to form a traction wire, and the pipeline or the cable is not bent when being arranged on the same side.

Example 4:

The difference from embodiment 3 is that a blocking mechanism 600 for preventing magnetic leakage is provided, and the blocking mechanism 600 is preferably connected with the tapered sleeve 105 by a screw structure.

Illustratively, a blocking mechanism 600 is disposed above the outer conductor sleeve 100, the blocking mechanism 600 being configured to block the passage of microwaves at the emission aperture 103 and allow the passage of gases to prevent leakage of microwave energy after the plasma is excited.

Specifically, barrier mechanism 600 is disposed above outer conductor sleeve 100, in close proximity to emission aperture 103, to ensure that microwave energy does not leak from emission aperture 103 after the plasma is excited. Ensuring that all microwave energy is used to excite the plasma rather than being uselessly dissipated into the environment. At the same time, the blocking mechanism 600 allows gas to circulate so that plasma can be smoothly discharged from the emission hole 103.

In some embodiments, barrier mechanism 600 employs a special material, such as a microwave absorbing material or a shielding material, such as a brass material, to effectively block the propagation of microwaves, and includes a microporous structure or a specific arrangement of voids that block microwave radiation but allow the passage of gas molecules.

Illustratively, the blocking mechanism 600 includes four blocking blocks 601, gaps exist between two adjacent blocking blocks 601, the four blocking blocks 601 enclose a cone structure, the diameter of the cone structure gradually decreases from bottom to top, the cone structure is provided with a central channel 602, the central channel 602 is configured to communicate with the emission hole 103 and the external environment, and the central channel 602 is coaxially disposed with the emission hole 103.

In the embodiment of the present invention, gaps exist between two adjacent blocking blocks 601, and these gaps allow gas to circulate and prevent microwaves from passing through at the same time, and the size and shape of the gaps can be specifically set according to actual requirements, where no limitation is made to ensure that gas can pass through smoothly, and microwaves are blocked effectively. Four baffle blocks 601 enclose a resultant cone structure, the diameter of which gradually decreases from bottom to top, helping to enhance the stability of the structure and helping to guide the gas flow.

The central channel 602 arranged in the cone structure is communicated with the emission hole 103 and the external environment, so that the plasma or the gas for exciting the plasma can be smoothly discharged through the emission hole 103, the central channel 602 and the emission hole 103 are coaxially arranged, namely, the central line of the central channel 602 coincides with the central line of the emission hole 103, and the structure is beneficial to keeping the consistency and stability of the gas flow. In general, the barrier mechanism 600 ensures the efficiency and safety of the microwave cold plasma generating device while allowing for efficient management of plasma and gases.

The device provided by the embodiment of the invention is convenient to assemble, and in an exemplary installation process, the cylindrical sleeve 104, the connecting pipe 501 and the microwave source connecting mechanism 400 are assembled, the limit gasket 301 is sleeved into the cylindrical part 201, and then the arrow part 202 is fixed with the cylindrical part 201 to fix the limit gasket 301, so that the inner conductor 200 and the limit gasket 301 are assembled into a whole, and the whole is placed into the cylindrical sleeve 104, so that the limit gasket 301 is installed in the annular groove 106, namely, the coaxial limit of the outer conductor sleeve 100 and the inner conductor 200 is realized. The cylindrical sleeve 104 and the conical sleeve 105 are connected through threads, and finally the blocking mechanism 600 and the conical sleeve 105 are connected, so that the microwave plasma generating device according to the embodiment of the invention is assembled, the blocking device can be assembled or disassembled according to the use requirement, the specific structure of the blocking device is not limited to the structure, the blocking device can be realized by adopting other existing blocking device structures, the structure is not limited herein, and the assembled structure is shown in fig. 2-4.

In operation, the microwave source connection mechanism 400 is connected to a microwave source, and then gas is injected from the gas inlet assembly 500 to turn on the microwave source switch. The microwave energy is focused at the tip 205 of the coaxial terminal so that the electric field strength is high there, the output power of the microwave source is adjusted, and when it reaches a certain preset value, the electric field strength at the tip 205 breaks down the gas nearby, generating a plasma. Because the embodiment of the invention uses the conical cavity and metal arrowhead type inner conductor 200 to excite the plasma, the microwave power required for excitation is lower, so that the temperature of the generated plasma is lower. The gas to be introduced may be argon, air, oxygen, nitrogen, helium, etc., and is not limited herein, and may be specifically set according to actual requirements.

The ion generating device of example 4 was tested with an input microwave power of 20W, and the test results are shown in fig. 7 to 10. Fig. 7 is a schematic diagram of an electric field distribution of the microwave plasma torch outside the cylindrical cavity 101 and the tapered cavity 102, fig. 8 is a schematic diagram of an electric field distribution of the microwave plasma torch inside the cylindrical cavity 101 and the tapered cavity 102, fig. 9 is a partially enlarged front view of an electric field distribution of the microwave plasma torch inside the tip portion 205, and fig. 10 is a partially enlarged top view of an electric field distribution of the microwave plasma torch inside the tip portion 205. As can be seen from the above, the distance between the tip 205 and the upper end of the conical sleeve 105 is the strongest, the maximum is 106V/m, the argon gas can be self-excited, and the field intensity is uniformly distributed with the center of the emission hole 103 as the center of symmetry, so that the plasma symmetrical with the inner conductor 200 in the axial direction can be generated.

In order to more clearly embody the advantages of the microwave cold plasma generating device provided by the embodiment of the present invention compared with the prior art, the device will be tested as follows, specifically as shown in the following embodiment 5:

Example 5:

On the basis of embodiment 4, the lower external connection part 203 of the columnar part 201 of the inner conductor 200 is set to be a cylinder with the diameter of 3mm, the microwave source connecting mechanism 400 is set to be an N-type head, the diameter of the first connecting end 401 of the N-type head is 1.27mm, the cylindrical sleeve 104 is in threaded connection with the conical sleeve 105, so that different conical sleeves 105 can be conveniently replaced according to requirements, the conical sleeve 105 is in threaded connection with the blocking mechanism 600, and the blocking mechanism 600 can be replaced or cancelled according to the length of plasma jet after excitation or the different practical application positions.

In the embodiment of the invention, the introduced gas is pure argon, the N-type head is connected with a microwave source through a cable, the microwave source is a magnetron, and in other embodiments, the microwave source can be a traveling wave tube, a beam tuning tube, a solid source and the like.

The microwave frequency may be any frequency point in the electromagnetic wave, such as 915MHz, 2450MHz, 5800MHz, etc. The length of the coaxial structure can be increased or decreased according to practical use requirements, so that the field strength at the tip of the conductor 200 in the device can be maximized at different frequencies. The microwave power can be adjusted, namely, the microwave power can be adjusted according to the type of the gas, or different microwave powers are used for the same gas so as to obtain plasmas with different properties, and the flow rate of the gas can also be adjusted. Illustratively, when argon is introduced, adjusting the microwave power may result in a plasma jet length in the range of 2-13.5mm.

Returning to the embodiment of the invention, the plasma generated by the device is used for treating facial skin, so as to achieve the purposes of resisting aging and promoting skin firmness. When the device is used, argon is excited to be introduced into the air inlet assembly 500 from the gas steel cylinder, after the cylindrical cavity 101 and the conical cavity 102 are filled with the gas, a microwave source is started, the output power of the microwave is regulated, high field intensity can be generated at the tip end 205, and the argon is broken down to perform gas discharge, so that an argon plasma jet is formed. When the microwave input power is 4.5W and the argon flow is 8.6L/min, the hand is placed at the tail end of the plasma jet for 30s, and the temperature of the finger is raised to 36.8 ℃, so that the finger has no heat sensation and pain sensation.

The barrier of the device is placed on the skin of a human face, the tail end of the plasma jet just strikes the skin, active free radicals and high-speed particles generated by the plasma act on the skin, the activity of the skin on the surface is stimulated, and the skin is re-refreshed to a beautiful and young state.

In the embodiment of the invention, the argon plasma effect is actually generated, and when the microwave input power of 2.45GHz is 6.16W and the argon flow is 2.5L/min, the length of the argon plasma is 13.5mm. When the argon flow rate was 0.9L/min, the minimum microwave maintenance power was 1.57W, and the plasma jet length at this time was 2mm. When the microwave input power is 8W, the argon flow ranges from 0.3L/min to 30L/min, and the plasma can be maintained. Regarding the safety problem, after the device is connected with a microwave source and plasma is excited, the microwave leakage condition is tested at each position of the equipment port, and the data obtained by monitoring is 190 mu W/cm ² at most, so that the microwave in the ion generating device provided by the embodiment of the invention hardly leaks.

The microwave low-temperature plasma can increase the excitation, ionization and dissociation processes of gas molecules, has more excited sub-state atoms, has ionization and dissociation degrees for the gas which are higher than those of other types of plasmas by an order of magnitude, such as radio frequency electric field plasmas, and has the advantages of high plasma density, high ionization degree, high energy and strong activity, and is easier to generate or initiate related physical and chemical reactions. Therefore, the efficiency is higher in the medical treatment depending on the active components of the plasma, and compared with the active particles generated by the prior art, the plasma generated by the device provided by the embodiment of the invention has the advantages of high electron temperature and high electron density, so that the application effect is more obvious.

In general, in conventional coaxial microwave plasma torch configurations, the discharge tip 205 is generally flush with the terminal end of the tapered sleeve 105, while in embodiments of the present invention, the terminal end of the tip 205 is not flush with the terminal end of the tapered sleeve 105, but rather is disposed such that the terminal end of the tapered sleeve 105 is longer than the discharge tip 205, which forms a tapered cavity at the coaxial terminal end that increases the electric field strength of the coaxial terminal end, thereby facilitating sustained plasma ignition. The metal arrowhead-type structure is arranged to generate high electric field intensity at the tip 205, which is conducive to generating plasma by self-exciting working gas under low power, thereby reducing energy consumption and improving efficiency, ensuring smooth gas circulation, and generating high field intensity at the tip, which is conducive to effective utilization of gas and ensuring uniform generation of plasma. The arrangement of the baffle is similar to that of a cut-off waveguide, so that microwave leakage is effectively prevented, high safety can be maintained even after plasma excitation, and the device can be directly placed on the surface of human skin for treatment without worrying about the risk of microwave radiation.

The device provided by the embodiment of the invention can maintain the generation of the plasma with extremely low power as low as 1.57W, so that the energy efficiency is improved, the stability of the device is also improved, and the generated plasma contains high-concentration hydroxyl radical active particles and high-energy particles, so that the effect is better, and the device is especially suitable for the fields of medical treatment, surface treatment and the like.

Meanwhile, the device provided by the embodiment of the invention has compact and small structure, is convenient to carry and assemble and is easy to mass produce. The detachable arrangement of the tip 205 of the inner conductor 200 and the conical sleeve 105 allows an operator to replace the corresponding components according to different microwave source frequencies, which is suitable for the production of different kinds of gases and plasmas. The air inlet assembly 500 is arranged adjacent to the microwave source connecting mechanism 400, so that an operator can conveniently hold the microwave source connecting mechanism by hand, and meanwhile, the air pipe and the cable can be bound and fastened, and the convenience in use is further improved.

The device not only can use argon gas, can also use multiple gases such as air, oxygen, nitrogen gas, helium gas, has increased the flexibility of using, can change conical outer conductor sleeve and metal arrowhead type inner conductor 200 of equidimension simultaneously according to different microwave frequency of use for the device can adapt to different application demands. The microwave cold plasma generating device provided by the embodiment of the invention has obvious advantages in the aspects of improving the plasma generating efficiency, reducing the energy consumption, enhancing the safety, improving the operation convenience and the like, and has higher practical application value.

It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

It should also be noted that, in the present document, the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate an orientation or a positional relationship based on that shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Moreover, relational terms such as "first" and "second" may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions, or order, and without necessarily being construed as indicating or implying any relative importance. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal.

The microwave cold plasma generating device based on the coaxial metal arrowhead type structure provided by the application is described in detail, and specific examples are applied to illustrate the principle and the implementation mode of the application, and the description of the examples is only used for helping to understand the application, and the content of the description is not to be construed as limiting the application. While various modifications of the embodiments and applications of the application will occur to those skilled in the art, it is not necessary and not intended to be exhaustive of all embodiments, and obvious modifications or variations of the application are within the scope of the application.

Claims

1. A coaxial metal arrowhead-based microwave cold plasma generating device, comprising:

The outer conductor sleeve (100) is arranged to be a peripheral structure of a plasma generation area, the inside of the outer conductor sleeve comprises a cylindrical cavity (101) and a conical cavity (102) which are arranged in a communicated mode, and an air source can be connected to the inside of the outer conductor sleeve (100);

An inner conductor (200) disposed within the outer conductor sleeve (100) and coaxially disposed with the outer conductor sleeve (100), an annular gap being formed between the inner conductor (200) and the outer conductor sleeve (100), the inner conductor (200) being configured to transmit microwave energy to a region of the tapered cavity (102);

Wherein the inner conductor (200) comprises a columnar part (201) and an arrow part (202), one end of the columnar part (201) is connected with a microwave source, and the other end of the columnar part is connected with the opposite side of the tip of the arrow part (202), and the columnar part (201) is used for transmitting microwave energy of the microwave source to the arrow part (202);

-the cylindrical portion (201) is located within the cylindrical cavity (101), and-the arrow-head portion (202) is located within the conical cavity (102);

The tip of the arrow part (202) is arranged on the tip side of the conical cavity (102), an emitting hole (103) is arranged on the outer conductor sleeve (100) on the tip side of the conical cavity (102), the tip end face of the arrow part (202) is lower than the end face of the emitting hole (103), and the emitting hole (103) is used for emitting the cold plasma into the external environment of the outer conductor sleeve (100);

The conical cavity (102) is configured to concentrate an electric field in microwave energy at the tip of the arrow (202), so that the electric field strength at the tip of the arrow (202) is increased, and the self-ignition excitation of the gas source to generate plasma is realized.

2. A coaxial metal arrowhead-based microwave cold plasma generator according to claim 1, wherein the outer conductor sleeve (100) comprises a cylindrical sleeve (104) and a conical sleeve (105), the cylindrical cavity (101) is located in the cylindrical sleeve (104), the conical cavity (102) is located in the conical sleeve (105), and the top of the cylindrical sleeve (104) is detachably connected with the bottom of the conical sleeve (105);

The diameter of the cylindrical cavity (101) is equal to the maximum diameter of the conical cavity (102).

3. A coaxial metal arrowhead-based microwave cold plasma generator according to claim 2, characterized in that a limiting mechanism (300) is provided in the outer conductor sleeve (100), the limiting mechanism (300) being arranged to limit the inner conductor (200) coaxially with the outer conductor sleeve (100).

4. A coaxial metal arrowhead-based microwave cold plasma generator according to claim 3, wherein an annular groove (106) is provided in the cylindrical sleeve (104), the limit mechanism (300) is a limit gasket (301), the limit gasket (301) is provided in the annular groove (106), and the limit gasket (301) and the outer conductor sleeve (100) are coaxially provided;

The limiting gasket (301) is provided with a through hole (302) at the center, the columnar portion (201) penetrates through the through hole (302), the arrow portion (202) is located above the limiting gasket (301), the limiting gasket (301) is provided with a plurality of vent holes (303), and the vent holes (303) are used for enabling a gas source in a cavity below the limiting gasket (301) to flow into the cavity above the limiting gasket (301).

5. A coaxial metal arrowhead-type structure-based microwave cold plasma generator according to claim 4, wherein the pillar portion (201) includes a lower external portion (203) and an upper internal portion (204) which are axially connected, the lower external portion (203) is connected with a microwave source connection mechanism (400), and the diameter of the through hole (302) is larger than the diameter of the upper internal portion (204) and smaller than the outer diameter of the lower external portion (203);

The arrow part (202) comprises a tip part (205) and a connecting part (206) which are axially connected, the connecting part (206) is of a hollow structure with a downward opening, and an upper inscription part (204) of the columnar part (201) can be inserted into the hollow structure;

The upper inscription part (204) is inserted into the hollow structure after penetrating through the through hole (302), and the limit gasket (301) is fixed at the joint of the columnar part (201) and the arrow part (202);

The outer diameter of the connection portion (206) is larger than the diameter of the through hole (302).

6. The coaxial metal arrowhead-based microwave cold plasma generator according to claim 5, wherein when the limit gasket (301) is fixed at the connection of the columnar portion (201) and the arrow portion (202), the upper end surface of the lower external portion (203) is attached to the bottom of the limit gasket (301), and the lower end surface of the connecting portion (206) is attached to the upper end of the limit gasket (301);

The upper inner joint part (204) is in threaded connection with the connecting part (206).

7. The coaxial metal arrowhead-based microwave cold plasma generator, as set forth in claim 5, characterized in that the microwave source connection mechanism (400) includes a first connection end (401) and a second connection end (402), a mounting plate (403) is disposed between the first connection end (401) and the second connection end (402), and the mounting plate (403) is fixedly connected with the bottom of the cylindrical sleeve (104) through a plurality of bolt mechanisms (404);

The first connecting end (401) penetrates through the bottom of the cylindrical sleeve (104) and is connected with the lower external connection portion (203) of the cylindrical portion (201), the mounting plate (403) and the second connecting end (402) are arranged on the outer side of the cylindrical sleeve (104), and the second connecting end (402) is used for connecting a microwave source.

8. A coaxial metal arrowhead-based microwave cold plasma generator according to claim 7, wherein an air inlet assembly (500) is arranged at the bottom of the cylindrical sleeve (104), the air inlet assembly (500) is communicated with the cylindrical cavity (101), the air inlet assembly (500) is arranged to be communicated with an air source pipeline at the outer side thereof, and the air source in the air source pipeline is conveyed into the cylindrical cavity (101);

The flow direction of the air source conveyed by the air inlet assembly (500) entering the cylindrical cavity (101) for the first time is the horizontal direction.

9. A coaxial metal arrowhead-based microwave cold plasma generator according to claim 1, characterized in that a blocking mechanism (600) is provided above the outer conductor sleeve (100), the blocking mechanism (600) being arranged to block microwaves from passing at the emission aperture (103) and to allow gas circulation, preventing microwave energy from leaking after plasma excitation.

10. The microwave cold plasma generating device based on a coaxial metal arrowhead type structure according to claim 9, wherein the blocking mechanism (600) includes four blocking blocks (601), a gap exists between two adjacent blocking blocks (601), four blocking blocks (601) enclose a cone structure, the diameter of the cone structure gradually decreases from bottom to top, the cone structure is provided with a central channel (602), the central channel (602) is configured to be communicated with the emitting hole (103) and the external environment, and the central channel (602) is coaxially configured with the emitting hole (103).