阅读说明：本技术 一种基于微波非线性器件的高效设备 (High-efficiency equipment based on microwave nonlinear device ) 是由 王清源 于 2021-09-10 设计创作，主要内容包括：本发明公布了一种基于微波非线性器件的高效设备的设计方案。微波等离子体在高强度光源、微波紫外线空气灭菌和工业废气治理、等离子体火炬和微波等离子体推进方面有重要应用。本发明采用耦合螺钉和矩形波导、圆波导、同轴线或者其它传输线实现了两个相互串接的谐振腔,其谐振频率分别对应该设备的运行频率和点火频率。微波源首先工作在点火频率点火成功,然后变化频率到运行频率高效地运行。本发明既能自动地被点燃,又可以高效率地运行,可以被应用到各种气体和液体的消毒杀菌处理、微波等离子体火炬、微波等离子体气相沉积、微波等离子体推进器等领域。(The invention discloses a design scheme of high-efficiency equipment based on a microwave nonlinear device. Microwave plasma has important applications in high intensity light sources, microwave ultraviolet air sterilization and industrial waste gas treatment, plasma torches and microwave plasma propulsion. The invention adopts a coupling screw and a rectangular waveguide, a circular waveguide, a coaxial line or other transmission lines to realize two resonant cavities which are connected in series, and the resonant frequencies of the two resonant cavities respectively correspond to the operating frequency and the ignition frequency of the equipment. The microwave source first operates at the ignition frequency to ignite successfully and then changes the frequency to the operating frequency to operate efficiently. The invention can be ignited automatically, can operate efficiently, and can be applied to the fields of disinfection and sterilization treatment of various gases and liquids, microwave plasma torches, microwave plasma vapor deposition, microwave plasma propellers and the like.)

1. A high-efficiency device based on a microwave nonlinear device is characterized by comprising a microwave source (1), a regulating circuit (2) and at least one nonlinear device (3) which are sequentially communicated; the adjusting circuit (2) and the nonlinear device (3) form a nonlinear load, and a port of the nonlinear load connected with the microwave source (1) is an input end; the nonlinear load has two states, a small signal state and a large signal state; the adjusting circuit (2) comprises at least one adjusting body (21), a first coupling structure (21A) and a second coupling structure (21B), wherein the first coupling structure (21A) is located at the front end of the adjusting body (21), and the second coupling structure (21B) is located at the rear end of the adjusting body (21); in small signals, the first coupling structure (21A), the second coupling structure (21B), and the adjusting body (21) between the first coupling structure (21A) and the second coupling structure (21B) together form a first resonant cavity, and the resonant frequency of at least one resonant mode of the first resonant cavity is f 1; and in large signals, the second coupling structure (21B), the adjusting body (21) between the second coupling structure (21B) and the nonlinear device (3), and the nonlinear device (3) together form a second resonant cavity, and the resonant frequency of at least one resonant mode of the second resonant cavity is f 2.

2. A microwave nonlinear device-based high efficiency apparatus according to claim 1, characterized in that after the microwave source (1) is turned on, the center frequency of the microwave output from the microwave source (1) is changed at least once from f2 to a certain frequency f 3.

3. A microwave nonlinear device-based high efficiency apparatus in accordance with claim 2 wherein f3 is equal to f1 or the relative error between f3 and f1 is less than five percent.

4. A microwave nonlinear device-based high efficiency apparatus in accordance with claim 1 wherein the Q values of the first cavity and the second cavity are both greater than or equal to 100 and less than or equal to 10000 in said small signal state.

5. A microwave nonlinear device-based high-efficiency apparatus according to claim 1, characterized in that both the first coupling structure (21A) and the second coupling structure (21B) are in a weak coupling state.

6. The microwave nonlinear device-based high-efficiency apparatus according to claim 1, wherein the adjusting body (21) is a section of transmission line or more than one section of transmission lines which are communicated with each other.

7. A microwave nonlinear device-based high efficiency apparatus in accordance with claim 4 wherein the transmission line is a rectangular waveguide.

8. A microwave nonlinear device-based high-efficiency apparatus in accordance with claim 4, characterized in that the transmission line further includes a coaxial line inner conductor (23), and the transmission line is a coaxial line.

9. The microwave nonlinear device-based high-efficiency equipment according to claim 6 is characterized in that a hollow pipe (24) is arranged inside the coaxial line inner conductor (23), a metal head (34) is arranged at the tail end of the outer conductor of the transmission line far away from the microwave source (1), a gas outlet hole (35) is formed in the center of the metal head (34), gas is input from the outside through at least one gas inlet pipe (25) into the hollow pipe (24), and the gas is sprayed out from the gas outlet hole (35) in the center of the metal head (34).

10. A microwave nonlinear device-based high-efficiency apparatus according to any one of claims 1 to 7, characterized in that the first coupling structure (21A) and the second coupling structure (21B) are coupling screws or metal diaphragms with through holes or a combination thereof; in the case of a coupling screw, the depth of the coupling screw into the adjusting body (21) can be changed from the outside and fixed, and the depth of the coupling screw into the adjusting body (21) is greater than 2/3 of the maximum travel of the coupling screw in the adjusting body (21); in the case of a metal diaphragm with through holes, the size of the through holes is smaller than 1/3 of the size of the metal diaphragm at least in one direction of the cross section.

Technical Field

The invention relates to high-efficiency equipment based on a microwave nonlinear device. In particular to a high-efficiency plasma device which realizes the automatic ignition of a gas plasma discharge device and works with high efficiency by utilizing an impedance matcher and a variable-frequency microwave source.

Background

Under the action of high-power microwaves, the gas is ionized, plasma is generated, and light is emitted. The high-intensity gas discharge lamp realized by exciting the plasma by utilizing the microwave has the advantages of high brightness, color spectrum close to sunlight, long service life, high luminous efficiency and the like, and can be widely applied to automobile headlights, square illumination and greenhouse vegetable light sources. The electrodeless ultraviolet lamp lighted by the microwave has the advantages of high brightness, long service life, high luminous efficiency and the like, can be widely used for sterilizing atmosphere and drinking water, and can also be used in the fields of industrial waste gas and industrial wastewater treatment and the like. The microwave plasma torch realized by utilizing the microwave ionized gas has the characteristics of high temperature, no pollution and quick start and stop, and has wide application in the aspects of motor vehicle engine ignition, large boiler ignition, metal cutting, surface cleaning and even surgical operation. The microwave plasma thruster generates plasma by utilizing microwave ionized gas, and is expected to provide a new power for space flight.

However, most microwave plasma devices exhibit strong non-linearity in their input impedance, and are strongly non-linear devices. At small signals, the gas is not ionized and the microwave absorption is weak. Most of the microwaves incident on the gas will be reflected. To ionize the gas, a strong microwave field strength is required. For example, at one atmosphere, the breakdown field strength of air is three million volts per meter. Under the action of high-power microwaves, the plasma formed after the gas is ionized can well absorb the microwaves. Early solutions require high power microwaves to ignite the plasma device. When the device is ignited, due to the severe impedance mismatch caused by the significant load change, most of the microwave energy is reflected, the microwave power absorbed by the plasma is small, and the energy efficiency of the device is low. The strong non-linearity of microwave plasma devices also makes low power microwave plasma devices difficult to implement.

Hong et al, 2011 reported a microwave plasma torch [ IEEE transitions ON PLASMA SCIENCE, VOL.39, NO.10, octber 2011, pp.1958-1962 ]. Wherein a moving tungsten filament is used to ignite the microwave plasma device manually. This method is not conducive to the automated operation of the apparatus. Christoph Schopp and Holger Heuermann in 2013 proposed a two-state matching scheme [ 2013, Proceedings of the 43rd European Microwave Conference, pp.881-884 ]. The scheme adopts a lumped parameter matching circuit and utilizes frequency switching to well solve the problems of automatic ignition and high-efficiency work of the gas discharge lamp. However, this method has several disadvantages: 1) the insertion loss of the matching circuit is large, and the energy efficiency of the scheme is seriously reduced. 2) In the commonly used microwave frequency band of 2450MHz, the power capacity of the lumped parameter circuit is relatively small. The application of this solution in industrial and environmental fields is limited by the power capacity. 3) The matching circuit of the scheme has a complex structure.

Disclosure of Invention

The invention aims to provide a microwave plasma device with simple structure, low insertion loss and high efficiency. In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a high-efficiency device based on microwave nonlinear devices comprises a microwave source, a regulating circuit and at least one nonlinear device which are sequentially communicated. The adjusting circuit and the nonlinear device form a nonlinear load, and a port of the nonlinear load connected with the microwave source is an input end. The nonlinear load has two states, a small signal state and a large signal state. The adjusting circuit comprises at least one adjusting body, a first coupling structure and a second coupling structure, wherein the first coupling structure is located at the front end of the adjusting body, and the second coupling structure is located at the rear end of the adjusting body. And in small signals, the first coupling structure, the second coupling structure, and the adjusting body between the first coupling structure and the second coupling structure together form a first resonant cavity, and the resonant frequency of at least one resonant mode of the first resonant cavity is f 1. And in small signal, the second coupling structure, the adjusting body between the second coupling structure and the nonlinear device, and the nonlinear device together form a second resonant cavity, and the resonant frequency of at least one resonant mode of the second resonant cavity is f 2.

In the present invention, the term "ignition" means that the gas in the nonlinear device is broken down to become plasma.

The small and large signals here may have different definitions for different nonlinear devices. For example, for a gas discharge device, a small signal therein indicates a signal when the gas is not broken down. The two states of the nonlinear load correspond to the states of the gas not broken down and the gas broken down, respectively. Typically, signals less than 1 milliwatt are signals and large signals have a power greater than 1 watt.

The resonant frequencies of the first and second resonant cavities may vary greatly with the state of the nonlinear device. Here, f2 and f1 denote the resonant frequencies of one resonant mode of the second resonant cavity and the first resonant cavity, respectively, in the case of a small signal.

The center frequency of the microwave source output microwaves changes at least once from f2 to a certain frequency f3 after the microwave source is turned on. In general, f3 equal to f1 may not be the best choice because when the nonlinear device is in a large signal state, the resonant frequency of the resonant mode of the first resonant cavity may deviate somewhat from the resonant frequency of the resonant mode of the nonlinear device when the nonlinear device is in a small signal. Therefore, we can set f3 equal to f1, but varying the search for the optimal f3 frequency within less than five percent of the relative error from f1 may be more effective.

The input impedance of the nonlinear device varies significantly with the magnitude of the microwave source output power. For example, at a microwave source output power of 1 milliwatt, the nonlinear device is in a small signal mode with its input impedance being primarily reactive. When the output power of the microwave source is 100 watts, the nonlinear device is in a large signal mode, and the input impedance of the nonlinear device is close to the characteristic impedance of the output end of the microwave source. The non-linear device herein may include a plasma discharge device having a discharge gas disposed therein, such as a gas discharge lamp bulb, an electrodeless ultraviolet lamp, a dielectric tube having a gas flowing therethrough, and the like.

The center frequency of the microwave source output microwave here needs to be changed at least once from f2 to f 3. There are two ways to "vary" among them. If the microwave source is a solid state source, "change" herein refers to "switching". If the microwave source is an electric vacuum oscillator, "variation" herein refers to "drift". For example, most typical electric vacuum oscillator magnetrons start up, the frequency of their output microwaves gradually decreases due to the temperature of their resonant cavity until they eventually stabilize.

Taking a microwave plasma nonlinear device as an example, the working principle of the invention is briefly described as follows. In general, before gas breakdown, the nonlinear device absorbs microwaves weakly and is in a small-signal state. The input impedance of the nonlinear device is dominated by reactance. The microwaves entering the nonlinear device are almost totally reflected back. The amplitude of the microwave electric field felt by the gas within the nonlinear device is small. The gas cannot be broken down.

A second coupling structure is arranged between the nonlinear device and the microwave source, and the nonlinear device form a second resonant cavity together. Before the gas breakdown, the loss of the resonant cavity is very small, and the Q value is very high. In order to effectively break down the gas therein, we need to satisfy two conditions: first, the frequency of the microwave source is equal to the frequency of the cavity, and is f2, or as close as possible. Secondly, the impedance of the microwave source and the resonant cavity at resonance is matched as much as possible. For the second requirement we need to set the coupling coefficient of the second coupling structure appropriately. The coupling coefficient of the second coupling structure will be low due to the high Q-value of the cavity.

After the gas is broken down, the nonlinear device is in a large signal state. The matching second cavity is no longer matched for small signals and most of the microwaves will be reflected. The operation efficiency of the apparatus will be low. The invention arranges a first coupling structure in front of a second coupling structure, the first coupling structure and the second coupling structure form a first coupling cavity, the frequency of the first coupling cavity is f1, and the coupling coefficient of the first coupling structure is adjusted, so that a microwave source, the first coupling cavity and a nonlinear device in a large signal state are matched at the frequency of f 1. Considering that the second coupling structure is in a weak coupling state, the first coupling structure must also be in a weak coupling state.

In order to realize that the nonlinear device effectively changes from a small signal state to a large signal state and then operates efficiently, the first coupling structure and the second coupling structure are in weak coupling states. In the small signal state, the Q values of the first resonator and the second resonator should be relatively high. In a specific case, the Q values of the first resonant cavity and the second resonant cavity are related to the microwave absorption performance of the nonlinear device in a small-signal state, for example, both Q values are greater than 100 and smaller than 10000.

The adjustment body and the non-linear device may be of any spatial shape. In a preferred design, the adjusting body is a section of transmission line, or more than one section of transmission lines which are communicated with each other. The transmission line may be a rectangular waveguide. The transmission line may further include a coaxial line inner conductor, which is a coaxial line.

In order to realize the plasma spray gun, a hollow pipe is arranged in the coaxial line inner conductor, a metal head is arranged at the tail end, far away from a microwave source, of the outer conductor of the transmission line, an air outlet hole is formed in the center of the metal head, air is input into the hollow pipe from the outside through at least one air inlet pipe, and the air is sprayed out of the air outlet hole in the center of the metal head.

In a preferred implementation, the first coupling structure and the second coupling structure are both coupling screws, the depth of the coupling screws entering the adjusting body can be changed from the outside and is fixed by nuts, and the depth of the coupling screws entering the adjusting body is greater than 2/3 of the maximum stroke of the coupling screws in the adjusting body. The maximum travel of the coupling screw inside the adjustment body is defined as the maximum length that the coupling screw can reach inside the adjustment body, provided that the tip of the coupling screw and the inner surface of the adjustment body opposite thereto are not in contact.

In order to achieve a weak coupling, the coupling screw needs to enter the adjustment body deep enough.

In another implementation, the first coupling structure and the second coupling structure are both metal diaphragms with through holes, and at least in one direction of the cross section, the size of the through holes is smaller than 1/3 of the size of the metal films. The metal diaphragm is a metal plate with a certain thickness and a certain shape, and a through hole is formed in the metal plate. In order to achieve weak coupling, the size of the via needs to be small enough.

In another implementation manner, either one of the first coupling structure and the second coupling structure is a metal diaphragm or a coupling screw with a through hole, and the other one is a metal diaphragm or a coupling screw with a through hole.

The application of the invention can be simply divided into three categories:

in a first type of application, at least one gas discharge lamp is arranged in the non-linear device. The invention can provide a high-quality light source with high brightness, long service life, high luminous efficiency and color spectrum close to sunlight. At this time, the casing of the nonlinear device is provided with a plurality of small holes, which can not only effectively prevent the microwave from leaking, but also can fully emit visible light.

In a second type of application, the non-linear device is passed through a discharge gas. The invention can provide a high-efficiency plasma torch or microwave plasma thruster.

In the third application, at least one electrodeless ultraviolet lamp tube is arranged in the nonlinear device. The electrodeless ultraviolet lamp tube is efficiently lightened by microwaves, so that air or water, particularly waste or wastewater, passes through the electrodeless lamp tube in a nonlinear device, and bacteria, viruses and harmful substances in the electrodeless ultraviolet lamp tube are effectively killed or degraded by ultraviolet light. At this time, the housing of the nonlinear device is provided with at least two holes, which can not only effectively prevent the microwave from leaking, but also allow gas and liquid to enter and flow out of the nonlinear device.

For convenience, the electromagnetic wave source herein is primarily in the microwave frequency range. The invention can also adopt millimeter wave with frequency higher than microwave, even terahertz frequency, and radio frequency with frequency lower than microwave. Meanwhile, the non-linear device herein is not limited to only gas discharge and plasma. Other devices that rely on strong non-linear effects and have significantly different load impedances before and during operation can be effectively started and operated with high efficiency using the present invention.

The invention has the following beneficial effects:

the invention discloses a design scheme of high-efficiency equipment based on a microwave nonlinear device. Microwave plasma has important applications in high intensity light sources, microwave ultraviolet air sterilization and industrial waste gas treatment, plasma torches and microwave plasma propulsion. The invention adopts a coupling screw and a rectangular waveguide, a circular waveguide, a coaxial line or other transmission lines to realize two resonant cavities which are connected in series, and the resonant frequencies of the two resonant cavities respectively correspond to the operating frequency and the ignition frequency of the equipment. The microwave source first operates at the ignition frequency to ignite successfully and then changes the frequency to the operating frequency to operate efficiently. The invention can be ignited automatically, can operate efficiently, and can be applied to the fields of disinfection and sterilization treatment of various gases and liquids, microwave plasma torches, microwave plasma vapor deposition, microwave plasma propellers and the like.

Drawings

FIG. 1 is a schematic side sectional view of the invention and example 1

FIG. 2 is a schematic top view of embodiment 2

FIG. 3 is a schematic top view of example 3

FIG. 4 is a schematic side sectional view of EXAMPLE 4

FIG. 5 is a schematic side sectional view of EXAMPLE 5

FIG. 6 is a schematic side sectional view of EXAMPLE 6

The reference numbers in the drawings correspond to the names: 1-microwave source, 2-regulating circuit, 21-regulating body, 21A-first coupling structure, 21B-second coupling structure, 23-coaxial line inner conductor, 24-hollow tube, 25-air inlet tube, 3-nonlinear device, 31-dielectric tube, 32-electrodeless lamp tube, 33-supporting dielectric plate, 34-metal head and 35-air outlet hole.

Detailed Description

Examples 1

As shown in fig. 1 and 2.

A high-efficiency device based on a microwave nonlinear device comprises a microwave source 1, a regulating circuit 2 and a nonlinear device 3 which are sequentially communicated. The adjusting circuit 2 and the nonlinear device 3 form a nonlinear load, and a port of the nonlinear load connected with the microwave source 1 is an input end. The nonlinear load has two states, a small signal state and a large signal state. The adjusting circuit 2 comprises at least one adjusting body 21 and a first coupling structure 21A located at the front end of the adjusting body 21 and a second coupling structure 21B located at the rear end of the adjusting body 21. And in the case of a small signal, the first coupling structure 21A, the second coupling structure 21B, and the adjusting body 21 between the first coupling structure 21A and the second coupling structure 21B together form a first resonant cavity, and a resonant frequency of at least one resonant mode of the first resonant cavity is f 1. And in the case of a small signal, the second coupling structure 21B, the adjusting body 21 between the second coupling structure 21B and the nonlinear device 3, and the nonlinear device 3 together form a second resonant cavity, and a resonant frequency of at least one resonant mode of the second resonant cavity is f 2. After the microwave nonlinear device-based high-efficiency equipment is changed from a small-signal state to a large-signal state, the center frequency of the microwave output by the microwave source 1 is changed from f2 to f3 at least once.

After the microwave source 1 is turned on, the center frequency of the microwave output by the microwave source 1 is changed at least once from f2 to a certain frequency f 3. The relative error between F3 and F1 is less than five percent.

And in the small-signal state, the Q values of the first resonant cavity and the second resonant cavity are both larger than 100 and smaller than 10000.

The first coupling structure 21A and the second coupling structure 21B are both weakly coupled.

The adjusting body 21 is a section of transmission line.

The transmission line is a rectangular waveguide.

The first coupling structure 21A and the second coupling structure 21B are both coupling screws, the depth of the coupling screws into the adjusting body 21 can be changed from the outside and is fixed by nuts, and the depth of the coupling screws into the adjusting body 21 is greater than 2/3 of the maximum stroke of the coupling screws in the adjusting body 21.

EXAMPLES example 2

As shown in fig. 2.

Compared with the embodiment example 1, the difference is only that:

the first coupling structure 21A and the second coupling structure 21B are both metal diaphragms. In the direction of the broad side of the rectangular waveguide, the size of the through hole is smaller than 1/3 of the size of the metal film.

EXAMPLE 3

As shown in fig. 3.

Compared with the implementation example 2, the nonlinear device comprises a four-in-one constant amplitude and constant phase power divider and a nonlinear sub-device respectively connected with four output ends of the divider.

EXAMPLE 4

As shown in fig. 4.

Thus, example 1 differs from example 1 only in that:

the nonlinear device comprises a section of rectangular waveguide with short-circuited end and a dielectric tube 31. The dielectric tube 31 passes through the rectangular waveguide from the wide side of the rectangular waveguide from the bottom to the top, and gas passes through the dielectric tube and can be ionized by microwaves inside the rectangular waveguide. And the plasma generated after ionization is sprayed upwards. The example of this implementation is a plasma torch.

EXAMPLE 5

As shown in fig. 5.

Compared with the embodiment example 1, the difference is only that:

the transmission line of the adjusting circuit 2 is a coaxial line comprising a coaxial line inner conductor 23. The nonlinear device is a pitch of circular waveguide with short-circuited terminals, and an electrodeless lamp tube 32 and two supporting dielectric plates 33 positioned at two ends of the electrodeless lamp tube are arranged in the nonlinear device along the axis of the nonlinear device.

EXAMPLE 6

As shown in fig. 6.

Compared with the embodiment example 5, the difference is only that:

without any electrodeless lamp 32.

Inside the coaxial line inner conductor a hollow tube 24 is arranged. As a nonlinear device, a metal head 34 is arranged at the tail end of the coaxial outer conductor far away from the microwave source 1, an air outlet hole 35 is formed in the center of the metal head, air is input from the outside through an air inlet pipe 25 into the hollow pipe 24, and the air is sprayed out from the air outlet hole 35 in the center of the metal head 34. By setting the frequency of the solid state source 1 to the ignition frequency, turning on the solid state source 1 and letting it have a frequency f1, it is convenient to successfully break down the gas in the vicinity of the metal head 34, creating a plasma. By switching the frequency of the solid state source 1 to the operating frequency, the temperature and length of the plasma flame can be optimized. Generally, the material of the air inlet pipe 25 is preferably medium. For the purpose of facilitating ignition, the metal head 34 has a gap between the coaxial line inner conductor 23 and the gap should be as small as possible.

The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. To facilitate commissioning of the device, conventional techniques such as adding an impedance tuner between the microwave source and the conditioning circuitry, providing tuning means in the first and second resonant cavities, etc. may be useful. Any modification, equivalent replacement, addition of any conventional technology, etc. to the above embodiment without departing from the best design, within the spirit and principle of the present invention, still fall within the protection scope of the technical solution of the present invention.