Microwave plasma torch generator

Abstract

The present disclosure provides a microwave plasma torch generating device, comprising: an input waveguide for inputting microwaves; a gradient waveguide, comprising a first gradient waveguide section and a second gradient waveguide section, the first gradient waveguide section and the second gradient waveguide section are used to distribute the power of microwaves to obtain a first microwave and a second microwave, wherein the power of the first microwave is higher than the power of the second microwave; a coaxial resonant cavity, used to generate a high-intensity electric field according to the second microwave; a quartz glass tube is a reaction cavity of a microwave plasma flame, used to generate a microwave plasma flame according to gas molecules under the action of a high-intensity electric field, and a cylindrical resonant cavity is used to generate an electric field of a certain intensity according to the first microwave to maintain the plasma flame. The plasma torch generated by the microwave plasma torch generating device has a larger plasma volume, a longer gas processing distance, does not require a mechanical ignition device for triggering, and consumes less energy.

Description

Technical Field

[0001] The present disclosure relates to the field of microwave plasma technology, and in particular to a microwave plasma torch generating device. Background Art

[0002] Plasma is the fourth state of matter, different from solid, liquid and gas. Plasma is an ionized gas, mainly composed of neutral atoms or molecules, excited atoms or molecules, free radicals, electrons or positive and negative ions, and radiated photons. Their negative charge number is the same as their positive charge number, so they are electrically neutral on a macroscopic scale. The principle of microwave plasma generation is to use a waveguide device to inject microwave energy into gas molecules, induce a series of reactions such as excitation and ionization of gas molecules, and then produce highly reactive plasma. The characteristics of the "hole structure" of the microwave electromagnetic field can confine the plasma generated by the excitation ionization to a specific space and realize the transmission of the plasma [1]. Compared with other methods of generating plasma, microwave plasma has many advantages, such as high ionization degree, wide pressure range, high electron density, easy control of microwave and plasma characteristics, etc. These characteristics make the research on microwave plasma technology have greater practical application value.

[0003] At one atmosphere of pressure, the breakdown field strength of air is 3×10 6 V / m. In order to generate the high electric field intensity required for plasma, the most commonly used solutions in microwave resonant cavities include the following two: increasing the microwave input power or reducing the size of the microwave resonant cavity. Increasing the microwave input power can increase the microwave field intensity per unit volume, which is beneficial to increase the electric field intensity, but the increase in microwave power is limited. Reducing the size of the microwave resonant cavity can make the electric field more concentrated, greatly enhance the field intensity, and facilitate implementation and personalized design. Therefore, the most commonly used traditional microwave plasma torch is a compressed waveguide structure, which can reduce the volume of the resonant cavity and concentrate the electric field to increase the electric field intensity; or a resonant cavity structure with multiple input ports to provide greater microwave power. However, the plasma volume generated by this resonant cavity structure is small, the gas processing distance is short, the isolation between multiple ports is difficult, higher power input is required, and usually an external mechanical ignition device is required for triggering. Summary of the invention

[0004] In view of the above technical problems, an embodiment of the present disclosure provides a microwave plasma torch generating device, comprising: an input waveguide for inputting microwaves; a gradient waveguide, comprising a first gradient waveguide segment and a second gradient waveguide segment, the first gradient waveguide segment and the second gradient waveguide segment being used to distribute the power of the microwaves to obtain a first microwave and a second microwave, wherein the power of the first microwave is higher than the power of the second microwave; a coaxial resonant cavity, for generating a high-intensity electric field according to the second microwave; and a cylindrical resonant cavity, a quartz glass tube being provided at the center, the quartz glass tube being a reaction cavity of a microwave plasma flame, for generating a microwave plasma flame according to gas molecules under the action of a high-intensity electric field, and the cylindrical resonant cavity being used to generate an electric field of a certain intensity according to the first microwave to maintain the plasma flame.

[0005] According to an embodiment of the present disclosure, the power distribution ratio of the first gradually changing waveguide section to the second gradually changing waveguide section to the microwave is 3:1.

[0006] According to an embodiment of the present disclosure, the microwave plasma torch generating device further includes: a connecting waveguide and a coupling port, wherein one end of the connecting waveguide is connected to the first gradient waveguide segment, and the other end is connected to the cylindrical resonant cavity through the coupling port to feed the first microwave into the cylindrical resonant cavity.

[0007] According to an embodiment of the present disclosure, the microwave plasma torch generating device further includes: a short-circuit waveguide connected to the second gradient waveguide section; a coupling probe connected to the short-circuit waveguide and used to concentrate the second microwave; a coaxial line inner conductor and a coaxial line outer conductor, the coaxial line outer conductor being sleeved on the outside of the coaxial line inner conductor and being coaxial with the coaxial line inner conductor, one end of the coaxial line inner conductor and the coaxial line outer conductor being connected to the coupling probe and the other end being connected to the coaxial resonant cavity, for transmitting the second microwave to the coaxial resonant cavity.

[0008] According to an embodiment of the present disclosure, the coaxial resonant cavity includes: a conductor inside the coaxial resonant cavity, used to generate a high-intensity electric field according to a second microwave; wherein one end of the conductor inside the coaxial resonant cavity is open-circuited and the other end is short-circuited, and the open end is inserted into a quartz glass tube; and the coaxial resonant cavity housing is used to support and fix the conductor inside the coaxial resonant cavity.

[0009] According to an embodiment of the present disclosure, the diameter of the conductor in the coaxial resonant cavity gradually decreases along the direction from the open-circuited end to the short-circuited end.

[0010] According to an embodiment of the present disclosure, an air inlet pipe is further provided at one end of the quartz glass tube close to the coaxial resonant cavity, and the air inlet pipe forms a preset angle with the central axis of the quartz glass tube.

[0011] According to an embodiment of the present disclosure, the air inlet pipes are symmetrically distributed on both sides of the central axis of the quartz glass tube.

[0012] According to an embodiment of the present disclosure, the surface of the quartz glass tube not covered by the cylindrical resonant cavity is covered with a metal cylinder.

[0013] According to an embodiment of the present disclosure, the input waveguide and the connecting waveguide are rectangular waveguides. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0015] Figure 1 A front view schematically shows the structure of a microwave plasma torch generating device according to an embodiment of the present disclosure.

[0016] Figure 2 A top view schematically shows the structure of a microwave plasma torch generating device according to an embodiment of the present disclosure.

[0017] [Description of Reference Numerals]

[0018] 1-input waveguide, 2-gradient waveguide, 201-first gradient waveguide section, 202-second gradient waveguide section, 3-coaxial resonant cavity, 301-coaxial resonant cavity inner conductor, 302-coaxial resonant cavity shell, 4-cylindrical resonant cavity, 5-quartz glass tube, 501-inlet pipe, 6-connecting waveguide, 7-coupling port, 8-short-circuit waveguide, 9-coupling probe, 10-coaxial line inner conductor, 11-coaxial line outer conductor, 12-metal cylinder. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0020] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0021] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0022] In the description of the present disclosure, it is necessary to understand that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the subsystem or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present disclosure.

[0023] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the present disclosure, any reference symbol between brackets should not be constructed as a limitation to the present disclosure.

[0024] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present disclosure, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0026] In order to solve the deficiencies of the prior art, the present disclosure provides a microwave plasma torch generating device, which is implemented based on a combined microwave resonant cavity and mainly consists of a waveguide assembly, a Y-shaped branch waveguide power divider, a probe waveguide-coaxial transition section, a cylindrical resonant cavity, a 1 / 4 wavelength coaxial resonant cavity, a quartz tube, an air inlet, etc. A similar introduction is given below in conjunction with a specific embodiment.

[0027] Figure 1 A front view schematically shows the structure of a microwave plasma torch generating device according to an embodiment of the present disclosure. Figure 2 A top view schematically shows the structure of a microwave plasma torch generating device according to an embodiment of the present disclosure.

[0028] like Figure 1 and Figure 2 As shown, in one embodiment of the present disclosure, a microwave plasma torch generating device may include, for example, an input waveguide 1, a gradient waveguide 2, a coaxial resonant cavity 3, a cylindrical resonant cavity 4 and a quartz glass tube 5.

[0029] Specifically, the input waveguide 1 is used to input the microwave M. Preferably, the input waveguide 1 can be, for example, a rectangular waveguide. The metal diaphragm of the gradient waveguide 2 is divided into two upper and lower parts, including a first gradient waveguide section 201 and a second gradient waveguide section 202. The first gradient waveguide section 201 and the second gradient waveguide section 202 are both connected to the output end of the input waveguide 1, and are used to distribute the power of the microwave M to obtain the first microwave and the second microwave. The power of the first microwave is higher than the power of the second microwave. Among them, the first gradient waveguide section 201 transmits the first microwave, and the second gradient waveguide section 202 transmits the second microwave, that is, the first gradient waveguide section 201 and the second gradient waveguide section 202 are equivalent to a power divider. Preferably, the power distribution ratio of the first gradient waveguide section 21 and the second gradient waveguide section to the microwave M is preferably 3:1.

[0030] The coaxial resonant cavity 3 receives the second microwave and generates a high-intensity electric field according to the second microwave, and the high-intensity electric field plays an ignition triggering role in the generation of microwave plasma flame. The quartz glass tube 5 is arranged at the center of the cylindrical resonant cavity 4 as a reaction cavity of the microwave plasma flame, and is used to generate a microwave plasma flame according to gas molecules under the ionization effect of the high-intensity electric field. The cylindrical resonant cavity 4 receives the first microwave and generates an electric field of a certain intensity according to the first microwave to maintain the plasma flame.

[0031] According to the microwave plasma torch generating device provided in this embodiment, based on a single microwave source, the gradient waveguide is set to a "Y"-shaped structure composed of a first gradient waveguide section and a second gradient waveguide section with different power distribution ratios, and a small part of the microwave energy input by the input waveguide is fed into the coaxial resonant cavity through the second gradient waveguide section. The coaxial resonant cavity generates a high-intensity electric field based on a small part of the microwave energy to ignite the gas molecules in the quartz glass tube to generate a microwave plasma flame, and most of the microwave energy input by the input waveguide is fed into the cylindrical resonant cavity through the first gradient waveguide section to generate an electric field of a certain intensity to maintain the plasma flame, thereby fully utilizing the advantages of the combined resonant cavity, and microwave plasma can be continuously generated without the need for an additional ignition device to trigger. In addition, although the electric field intensity at the center of the cylindrical resonant cavity is small, while maintaining the plasma flame, a larger volume of plasma flame can be formed and the gas processing distance is longer.

[0032] Continue reading Figure 1 and Figure 2 In another embodiment of the present disclosure, the microwave plasma torch generating device may further include a connecting waveguide 6 and a coupling port 7, one end of the connecting waveguide 6 is connected to the first gradient waveguide section 201, and the other end is connected to the cylindrical resonant cavity 4 through the coupling port 7 to feed the first microwave into the cylindrical resonant cavity 4. The cylindrical resonant cavity 4, the quartz glass tube 5 and the coupling port 7 constitute a component for maintaining the torch. Preferably, the connecting waveguide 6 may be, for example, a rectangular waveguide.

[0033] According to the microwave plasma torch generating device provided in this embodiment, by providing a connecting waveguide and a coupling port, it can better ensure that most of the energy is fed into the cylindrical resonant cavity.

[0034] In another embodiment of the present disclosure, the microwave plasma torch generating device may further include a short-circuit waveguide 8, a coupling probe 9, a coaxial inner conductor 10, and a coaxial outer conductor 11. The short-circuit waveguide 8 is connected to the second gradient waveguide section 202, and is used to short-circuit the microwave transmitted by the second gradient waveguide section 202. The coupling probe 9 is connected to the short-circuit waveguide 8, and is used to concentrate the second microwave. The coaxial outer conductor 11 is sleeved outside the coaxial inner conductor 10 and is coaxial with the coaxial inner conductor 10. One end of the coaxial inner conductor 10 and the coaxial outer conductor 11 are connected to the coupling probe 9, and the other end is connected to the coaxial resonant cavity 3, and is used to transmit the second microwave to the coaxial resonant cavity 3. Specifically, the second gradient waveguide section 202 first transfers a small portion of the microwave energy through the waveguide to coaxial interface, and then connects the inner and outer conductors of the coaxial line to the right input port of the coaxial resonant cavity 3, and finally feeds the energy into the coaxial resonant cavity 3 through ring coupling.

[0035] According to the microwave plasma torch generating device provided in this embodiment, by providing a short-circuit waveguide, a coupling probe, a coaxial inner conductor and a coaxial outer conductor, a small portion of microwave energy can be better concentrated so that the coaxial resonant cavity can generate a high-intensity electric field.

[0036] In another embodiment of the present disclosure, the coaxial resonant cavity 3 may include, for example, a coaxial resonant cavity inner conductor 301 and a coaxial resonant cavity shell 302, wherein the coaxial resonant cavity inner conductor 301 is used to generate a high-intensity electric field according to the second microwave; wherein one end of the coaxial resonant cavity inner conductor 301 is open-circuited and the other end is short-circuited, and the open end is inserted into the quartz glass tube 5, and the coaxial resonant cavity shell 302 is used to support and fix the coaxial resonant cavity inner conductor 301. Preferably, the coaxial resonant cavity 3 may be, for example, a 1 / 4 wavelength coaxial resonant cavity.

[0037] Furthermore, along the direction from the open end to the short-circuited end, the diameter of the conductor 301 in the coaxial resonant cavity gradually decreases, that is, the coaxial resonant cavity 3 adopts a gradual structure, the diameter of the open end is smaller, and the electric field is more concentrated.

[0038] According to the microwave plasma torch generating device provided in this embodiment, by opening one end of the conductor in the coaxial resonant cavity and short-circuiting the other end, and the diameter of the open end is smaller than the diameter of the short-circuited end, the open end of the coaxial resonant cavity can generate a high-intensity electric field, which fully meets the ignition requirements of the plasma torch. In addition, a small part of the open end is inserted into the quartz glass tube, so that the field intensity is concentrated to generate tip ignition, which stimulates the generation and maintenance of the plasma torch.

[0039] In another embodiment of the present disclosure, an inlet pipe 501 is further provided at one end of the quartz glass tube 5 close to the coaxial resonant cavity 3. The inlet pipe 501 and the central axis of the quartz glass tube 5 may form a preset angle, which is generally an acute angle. Preferably, the inlet pipes 501 are symmetrically distributed on both sides of the central axis of the quartz glass tube 5. The gas enters the quartz glass tube 5 from the inlet pipes 501 on both sides of the coaxial resonant cavity.

[0040] According to the microwave plasma torch generating device provided in this embodiment, the air inlet pipe at the bottom of the quartz tube forms a certain angle with the central axis to generate a spiral airflow, thereby preventing the high-temperature torch from melting the quartz tube wall.

[0041] In another embodiment of the present disclosure, the surface of the quartz glass tube 5 not covered by the cylindrical resonant cavity 4 may be covered with a metal cylinder 12, for example. Figure 1 As shown in FIG. 1 , the upper and lower outer sides of the quartz glass tube 5 are covered with metal cylinders 12 .

[0042] According to the microwave plasma torch generating device provided in this embodiment, the surface of the quartz glass tube not covered by the cylindrical resonant cavity is covered with a metal cylinder, which can prevent microwave leakage.

[0043] In order to verify the advantages of the above-mentioned microwave plasma torch generating device, the embodiment of the present disclosure also conducts simulation experiments.

[0044] Specifically, the cylindrical resonant cavity operates in the TM mode. 010 The electric field direction is constant along the axial direction, and the field value is the largest at the center axis of the cylinder. When the input power is 1W, the CST simulation shows that the peak value of the electric field intensity at the open end of the coaxial resonant cavity is greater than 1×10 5 V / m, the electric field at the axis of the cylindrical resonant cavity is about 1×10 4 V / m.

[0045] Based on this, it can be seen that the microwave plasma torch generating device provided in the embodiment of the present disclosure can complete the breakdown of air under atmospheric pressure and form a large-volume plasma torch under the condition of relatively small microwave power input. After simulation calculation, the design requirements can be met when the input power is 1.5kW.

[0046] In summary, compared with the traditional compressed waveguide plasma torch, the microwave plasma torch generating device provided by the embodiment of the present disclosure has a larger plasma volume, a longer gas processing distance, does not require a mechanical ignition device for triggering, and consumes less energy.

[0047] It should be noted that the microwave plasma torch generating device provided in the embodiment of the present disclosure can be actually applied to waste exhaust gas treatment, material surface treatment, biomedicine and other applications.

[0048] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A microwave plasma torch generating device, comprising: An input waveguide (1) for inputting microwaves; A gradient waveguide (2), comprising a first gradient waveguide section (201) and a second gradient waveguide section (202), wherein the first gradient waveguide section (201) and the second gradient waveguide section (202) are used to distribute the power of the microwave to obtain a first microwave and a second microwave, wherein the power of the first microwave is higher than the power of the second microwave; and the distribution ratio of the power of the microwave by the first gradient waveguide section (201) and the second gradient waveguide section (202) is 3:1; A coaxial resonant cavity (3), used for generating a high-intensity electric field according to the second microwave; A cylindrical resonant cavity (4) is provided with a quartz glass tube (5) at the center thereof, the quartz glass tube (5) being a reaction cavity of a microwave plasma flame and being used to generate the microwave plasma flame according to gas molecules under the action of the high-intensity electric field, the cylindrical resonant cavity (4) being used to generate an electric field of a certain intensity according to the first microwave to maintain the plasma flame; A short-circuit waveguide (8) connected to the second gradient waveguide section (202); A coupling probe (9), connected to the short-circuit waveguide (8), and used to concentrate the second microwave; A coaxial inner conductor (10) and a coaxial outer conductor (11), wherein the coaxial outer conductor (11) is sleeved outside the coaxial inner conductor (10) and is coaxial with the coaxial inner conductor (10), and one end of the coaxial inner conductor (10) and the coaxial outer conductor (11) are connected to a coupling probe (9) and the other end is connected to the coaxial resonant cavity (3), and is used to transmit the second microwave to the coaxial resonant cavity (3).

2. The microwave plasma torch generating device according to claim 1, wherein: The microwave plasma torch generating device also includes: A connecting waveguide (6) and a coupling port (7), wherein one end of the connecting waveguide (6) is connected to the first gradient waveguide section (201), and the other end is connected to the cylindrical resonant cavity (4) through the coupling port (7), so as to feed the first microwave into the cylindrical resonant cavity (4).

3. The microwave plasma torch generating device according to claim 1, wherein: The coaxial resonant cavity (3) comprises: A conductor (301) in a coaxial resonant cavity, used to generate a high-intensity electric field according to the second microwave; wherein one end of the conductor (301) in the coaxial resonant cavity is open-circuited and the other end is short-circuited, and the open end is inserted into the quartz glass tube (5); The coaxial resonant cavity housing (302) is used to support and fix the conductor (301) in the coaxial resonant cavity.

4. The microwave plasma torch generating device according to claim 3, wherein: Along the direction from the open circuit end to the short circuit end, the diameter of the conductor (301) in the coaxial resonance cavity gradually decreases.

5. The microwave plasma torch generating device according to claim 1, wherein: An air inlet pipe (501) is also provided at one end of the quartz glass tube (5) close to the coaxial resonant cavity (3); the air inlet pipe (501) forms a preset angle with the central axis of the quartz glass tube (5).

6. The microwave plasma torch generating device according to claim 5, wherein: The air inlet pipes (501) are symmetrically distributed on both sides of the central axis of the quartz glass tube (5).

7. The microwave plasma torch generating device according to claim 1, wherein: The surface of the quartz glass tube (5) not covered by the cylindrical resonant cavity (4) is covered with a metal cylinder (12).

8. The microwave plasma torch generating device according to claim 2, wherein: The input waveguide (1) and the connecting waveguide (6) are rectangular waveguides.

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