Plasma jet generation characteristic regulation and control device and method based on pipe wall temperature

Abstract

The invention discloses a plasma jet generation characteristic regulation and control device and method based on tube wall temperature, and the device comprises a dielectric barrier tube which is made of a heat-resistant insulating material and is used for generating a plasma jet at an outlet of the dielectric barrier tube when rare gas is introduced into the dielectric barrier tube and discharge voltage is applied between a high-voltage electrode and a ground electrode; the high-voltage electrode is arranged in the dielectric barrier tube and is used for applying discharge voltage to generate plasma; the ground electrode is arranged opposite to the high-voltage electrode and is used for being matched with the high-voltage electrode to form a discharge path in the dielectric barrier tube; and the heating device is arranged to change the generation and propagation characteristics of the ionization waves by regulating and controlling the pipe wall temperature of the dielectric barrier pipe, so as to regulate and control the length and the chemical activity of the plasma jet. According to the invention, the length of the plasma jet can be greatly increased and the chemical activity of the plasma can be improved without changing any power supply parameters, electrode structure parameters, working gas parameters and the like.

Description

Technical Field

[0001] The present invention relates to intelligent manufacturing processing technology, and in particular to a plasma jet generation characteristic control device and method. Background Art

[0002] Plasma is a complex system composed of active particles such as electrons, ions, free radicals, photons, etc. It has the characteristics of high energy, high activity, high selectivity, etc., and can realize a variety of physical and chemical processes, such as ionization, excitation, dissociation, oxidation, reduction, etc. Plasma jet is an atmospheric pressure non-equilibrium plasma source that can separate the plasma generation area and the working area in space. It has the advantages of low temperature, mild discharge, and high active particle production. It can be applied to material surface treatment, biomedicine, environmental engineering and other fields.

[0003] The length of the jet determines the range of the material surface that it can cover and process, and also affects its contact time with the material surface and the concentration of active particles. The longer the jet length, the farther the jet can propagate and expand, better maintain its stability and activity, and achieve better processing effects in different fields. Therefore, increasing the length of the plasma jet will help its further application in the future.

[0004] Scholars at home and abroad have conducted in-depth research on plasma jets and proposed a variety of methods to increase the length of plasma jets, such as designing new electrode structures, increasing the amplitude and frequency of the discharge voltage, and increasing the flow rate of the working gas. However, the special design of the electrode structure is not universal. The increase in discharge voltage and frequency will increase energy consumption, and increasing the flow rate of the working gas will increase gas consumption and cost. Finding a simple and reliable method to increase the length of the plasma jet will have a good promoting effect on its further application.

[0005] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0006] The main purpose of the present invention is to solve the problems existing in the above-mentioned background technology and to provide a device and method for regulating the generation characteristics of a plasma jet based on tube wall temperature.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A device for controlling the generation characteristics of a plasma jet based on tube wall temperature, comprising:

[0009] a dielectric barrier tube, which is made of a heat-resistant insulating material, is used to pass a working gas into the tube, and when a discharge voltage is applied between the high-voltage electrode and the ground electrode, a plasma jet is generated at the outlet thereof;

[0010] A high voltage electrode, which is disposed inside the dielectric barrier tube and is used to apply a discharge voltage to generate plasma;

[0011] A ground electrode, which is arranged opposite to the high-voltage electrode and is used to cooperate with the high-voltage electrode to form a discharge path in the dielectric barrier tube;

[0012] A heating device is arranged to change the generation and propagation characteristics of the ionization wave by regulating the wall temperature of the dielectric barrier tube, thereby regulating the length and chemical activity of the plasma jet.

[0013] Furthermore, the material of the dielectric barrier tube is a thermally conductive material such as quartz glass or alumina ceramics, but the present invention is not limited thereto.

[0014] Furthermore, the high-voltage electrode is made of a conductive material, such as a tungsten needle, a copper rod or a stainless steel rod, which is not limited in the present invention.

[0015] Furthermore, the heating device is arranged in a region between the ground electrode and an outlet of the dielectric barrier tube.

[0016] Furthermore, the discharge voltage applied between the high voltage electrode and the ground electrode is an alternating voltage or a pulse voltage.

[0017] Furthermore, the ground electrode and the high voltage electrode adopt a single electrode, a double electrode or a multi-group electrode structure.

[0018] Furthermore, the cross-sectional shape of the electrode structure of the ground electrode may be circular, square, or polygonal, but the present invention is not limited thereto.

[0019] Furthermore, the working gas flowing through the dielectric barrier tube is a rare gas or a rare gas containing a small amount of doping gas.

[0020] A method for regulating plasma jet generation characteristics based on tube wall temperature, using the plasma jet generation characteristics regulating device to regulate the length and chemical activity of the plasma jet.

[0021] The present invention has the following beneficial effects:

[0022] The present invention proposes a method for regulating a plasma jet by means of a dielectric tube temperature, which can significantly increase the length of the plasma jet and enhance its plasma chemical activity without changing any power supply parameters, electrode structure parameters, working gas parameters, etc.

[0023] The principle of increasing the length of the plasma jet of the present invention is that the plasma jet is actually a macroscopic manifestation of the propagation process of the ionization wave (plasma bullet) when a voltage is applied, so adjusting the length and chemical activity of the plasma jet is to adjust the propagation distance and intensity of the ionization wave. The formation of the ionization wave starts with the streamer discharge between the high-voltage electrode and the ground electrode, and the intensity of the streamer discharge depends on the size of the space charge density. There are "shallow potential wells" on the surface of the dielectric barrier material that adsorb free electrons, and the mechanism of releasing free electrons from the "shallow potential well" has an important influence on the density of the space charge. When the temperature of the dielectric barrier discharge increases, the vibration energy of the ions on the dielectric barrier surface increases, and the energy of the electrons in the "shallow potential well" increases, which is more conducive to breaking free from the bondage and increasing the space charge density. After the space charge density increases, the initial streamer discharge intensity increases, the ionization wave energy increases, and it can propagate a longer distance when other conditions remain unchanged, and the plasma jet has a higher plasma chemical activity.

[0024] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a plasma jet device in the prior art, showing the plasma jet length when the tube wall temperature is not adjusted.

[0026] Figure 2 This is a schematic diagram of a plasma jet control device based on tube wall temperature according to an embodiment of the present invention, showing the plasma jet length after adjusting the tube wall temperature.

[0027] Figure 3 This is a diagram showing the improvement effect of plasma jet length and plasma chemical activity according to an embodiment of the present invention (experimental photo). DETAILED DESCRIPTION

[0028] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

[0029] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for fixing as well as for coupling or communication.

[0030] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0031] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] See also Figure 2 The embodiment of the present invention provides a device for regulating the generation characteristics of a plasma jet based on the tube wall temperature, comprising: a dielectric barrier tube 1, which is made of a heat-resistant insulating material and is used to pass a working gas into the inside and generate a plasma jet at its outlet when a discharge voltage is applied between a high-voltage electrode 2 and a ground electrode 3; a high-voltage electrode 2, which is arranged inside the dielectric barrier tube 1 and is used to apply a discharge voltage to generate plasma; a ground electrode 3, which is arranged opposite to the high-voltage electrode 2 and is used to cooperate with the high-voltage electrode 2 to form a discharge path in the dielectric barrier tube 1; a heating device 4, which is arranged to change the generation and propagation characteristics of an ionization wave by regulating the tube wall temperature of the dielectric barrier tube 1, thereby regulating the length and chemical activity of the plasma jet.

[0033] In some embodiments, the material of the dielectric barrier tube 1 may be a conductive material such as quartz glass or alumina ceramics, but the present invention is not limited thereto.

[0034] In some embodiments, the high voltage electrode 2 may be a tungsten needle, a copper rod, or a stainless steel rod, but the present invention is not limited thereto.

[0035] See also Figure 2 In some embodiments, the heating device 4 is disposed in a region between the ground electrode 3 and the outlet of the dielectric barrier tube 1 .

[0036] In some embodiments, the discharge voltage applied between the high voltage electrode 2 and the ground electrode 3 may be an alternating voltage or a pulse voltage.

[0037] In some embodiments, the ground electrode 3 and the high voltage electrode 2 may adopt a single electrode, a double electrode or a multi-electrode structure.

[0038] In some embodiments, the cross-sectional shape of the electrode structure of the ground electrode 3 may be circular, square, or polygonal, but the present invention is not limited thereto.

[0039] In some embodiments, the working gas flowing through the dielectric barrier tube 1 may be a rare gas or a rare gas containing a small amount of dopant gas.

[0040] The embodiment of the present invention also provides a method for regulating the generation characteristics of a plasma jet based on the tube wall temperature, and uses the plasma jet generation characteristics regulating device to regulate the length and chemical activity of the plasma jet.

[0041] The specific embodiments of the present invention are further described below.

[0042] Schematic diagram of the plasma jet control device based on tube wall temperature Figure 2 shown.

[0043] The plasma jet generating device comprises a dielectric barrier tube 1, a high voltage electrode 2, a ground electrode 3 and a heating device 4. The material used for the dielectric barrier tube 1 can be quartz glass, alumina ceramics or any dielectric barrier material with a high heat resistance temperature. The high voltage electrode 2 can be made of common metal materials such as tungsten needles, copper rods, stainless steel rods, etc. The material of the ground electrode 3 can be made of metal materials with good electrical conductivity and heat resistance. The heating device 4 can be any device that adjusts the temperature of the dielectric barrier tube and does not cause liquid or solid pollution to the dielectric barrier tube. Specifically, resistance heating (the heating wire is placed in a specific area outside the jet tube) and thermal fluid heating are all possible. The electrode structure can be placed in an atmospheric pressure environment or other environments. A rare gas is introduced into the dielectric barrier tube, and a discharge voltage is applied between the high voltage electrode and the ground electrode, so that a plasma jet can be generated at the outlet of the jet tube. A heating device is set in the ionization wave generation and propagation area of ​​the jet tube, which can increase the plasma jet length by more than 2 times at most. It has been verified by experiments that when the heating temperature is set at about 400-500 degrees Celsius, the jet length can be increased by more than 2 times (ie, the jet length is 3 times the original length). Other preferred conditions include: pure helium flow rate of 12L / min, nanosecond pulse voltage rising edge of 50ns, and amplitude of 3.5kV.

[0044] Based on this device, the present invention proposes a method for regulating the plasma jet by the temperature of a dielectric tube, which can greatly increase the length of the plasma jet and improve its plasma chemical activity without changing any power supply parameters, electrode structure parameters, working gas parameters, etc.

[0045] The principle of this method to increase the length of the plasma jet is that the plasma jet is actually a macroscopic manifestation of the propagation process of the ionization wave (plasma bullet) when a voltage is applied, so adjusting the length and chemical activity of the plasma jet is to adjust the propagation distance and intensity of the ionization wave. The formation of the ionization wave starts with the streamer discharge between the high-voltage electrode and the ground electrode, and the intensity of the streamer discharge depends on the size of the space charge density. There are "shallow potential wells" on the surface of the dielectric barrier material that adsorb free electrons, and the mechanism of releasing free electrons from the "shallow potential well" has an important influence on the density of the space charge. When the temperature of the dielectric barrier discharge increases, the vibration energy of the ions on the surface of the dielectric barrier increases, and the energy of the electrons in the "shallow potential well" increases, which is more conducive to breaking free from the constraints and increasing the space charge density. After the space charge density increases, the initial streamer discharge intensity increases, the ionization wave energy increases, and it can propagate a longer distance when other conditions remain unchanged, and the plasma jet has a higher plasma chemical activity. The effect comparison diagram of the present invention is as follows Figure 3 shown. Figure 3 The improvement effect of plasma jet length and plasma chemical activity is shown (experimental photos).

[0046] A method for regulating plasma jet by the temperature of a dielectric tube of an electrode structure. The temperature of the dielectric tube is adjusted by an external heating device. In the present invention, the position of the external heating device is not limited, but the preferred position is the position between the cathode, anode and the outlet of the dielectric tube. The voltage waveform, frequency and positive and negative polarity applied by the electrode structure are not limited, preferably a nanosecond pulse voltage waveform, and a positive polarity voltage is applied to the anode. The electrode structure is not limited, and can be a single electrode, a double electrode and a multi-group electrode structure. The size of the electrode structure is not limited, and the inner diameter can be greater than or equal to 1mm. The cross-sectional shape of the electrode structure is not limited, and can be circular, square, polygonal, etc., preferably circular. The material of the dielectric tube is not limited, and it only needs to be a heat-resistant material, such as quartz glass, alumina ceramics, etc. The working gas flowing through the dielectric tube is a rare gas or a rare gas doped with a small amount of other gases. The flow rate of the working gas is not limited. The discharge environment of the plasma jet is not limited.

[0047] The core idea of ​​the present invention is to control the plasma jet by controlling the temperature of the dielectric tube. Under any form of power supply parameters, electrode structure parameters, and working gas parameters, the scheme of controlling the length of the plasma jet by controlling the temperature of the dielectric tube is within the protection scope of the present invention.

[0048] The power supply parameters of the embodiment of the present invention are not limited, and can be any plasma power supply with any waveform such as AC tube, pulse source, RF source, etc., and the voltage waveform is not limited. The electrode structure parameters include the number of electrodes, size, material, and positive and negative polarity. The dielectric tube material, size, and shape are not limited. The working gas parameters are not limited, including the type of rare gas, the ratio of the doping gas type, the flow rate, and the discharge space environment.

[0049] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A device for controlling the generation characteristics of a plasma jet based on tube wall temperature, characterized in that: include: a dielectric barrier tube, which is made of a heat-resistant insulating material, is used to pass a working gas into the tube, and when a discharge voltage is applied between the high-voltage electrode and the ground electrode, a plasma jet is generated at the outlet thereof; A high voltage electrode, which is disposed inside the dielectric barrier tube and is used to apply a discharge voltage to generate plasma; A ground electrode, which is arranged opposite to the high-voltage electrode and is used to cooperate with the high-voltage electrode to form a discharge path in the dielectric barrier tube; A heating device is arranged to change the generation and propagation characteristics of the ionization wave by regulating the wall temperature of the dielectric barrier tube, thereby regulating the length and chemical activity of the plasma jet.

2. The plasma jet generation characteristic control device according to claim 1, characterized in that: The dielectric barrier tube is made of a heat-conducting material.

3. The plasma jet generation characteristic control device according to claim 1 or 2, characterized in that: The high voltage electrode is made of conductive material.

4. The plasma jet generation characteristic control device according to any one of claims 1 to 3, characterized in that: The heating device is arranged in the discharge area, that is, the ionization wave generation and propagation area.

5. The plasma jet generation characteristic control device according to any one of claims 1 to 4, characterized in that: The discharge voltage applied between the high voltage electrode and the ground electrode is an alternating voltage or a pulse voltage.

6. The plasma jet generation characteristic control device according to any one of claims 1 to 5, characterized in that: The ground electrode and the high voltage electrode adopt a single electrode, a double electrode or a multi-group electrode structure.

7. The plasma jet generation characteristic control device according to any one of claims 1 to 6, characterized in that: The cross-sectional shape of the electrode structure of the ground electrode can be circular, square or polygonal.

8. The plasma jet generation characteristic control device according to any one of claims 1 to 7, characterized in that: The working gas flowing through the dielectric barrier tube is a rare gas or a rare gas containing a small amount of doping gas.

9. A method for controlling the generation characteristics of a plasma jet based on tube wall temperature, characterized in that: The plasma jet generation characteristic control device as claimed in any one of claims 1 to 8 is used to control the length and chemical activity of the plasma jet.

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