CN215865061U - Experimental detection device for cathode layer in surface dielectric barrier discharge - Google Patents
Experimental detection device for cathode layer in surface dielectric barrier discharge Download PDFInfo
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- CN215865061U CN215865061U CN202122190364.9U CN202122190364U CN215865061U CN 215865061 U CN215865061 U CN 215865061U CN 202122190364 U CN202122190364 U CN 202122190364U CN 215865061 U CN215865061 U CN 215865061U
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Abstract
The utility model belongs to the technical field of atmospheric pressure low-temperature plasma application, and relates to an experimental detection device for a cathode layer in surface dielectric barrier discharge. The utility model can quickly and conveniently detect the cathode layer and realize the comparison of the thickness of the cathode layer generated by different dielectric barrier discharge plasma exciters along the surface, the direct current power supply provides scanning bias voltage, the experimental detection of the cathode layer is realized by comparing the shielding capability of different exciters on the same bias voltage, a large gap of the cathode layer in the experimental comparison is filled, and the foundation is laid for the subsequent experimental research of the cathode layer.
Description
Technical Field
The utility model belongs to the technical field of atmospheric pressure low-temperature plasma application, and relates to an experimental detection device for a cathode layer in surface dielectric barrier discharge.
Background
Numerical simulation studies in the dielectric barrier discharge along the surface find that a strong breakdown field area exists near the edge of the exposed electrode. This area does not move and is very narrow and largeAbout several tens of microns, similar to the sheath structure in low pressure discharge. This sheath-like structure results from a glow-like discharge process when the exposed electrode is negative in polarity with respect to the dielectric surface and is therefore referred to as the cathode layer. The charged particles in the cathode layer form a dipole. The positive ions drift toward the exposed electrode and the maximum density occurs at the edge of the exposed electrode. The electrons drift to the surface of the medium to form a main discharge area and show a relatively uniform glow-like discharge mode. Due to the difference in mass, the drift velocity of the ions is lower than that of the electrons, resulting in a positive potential distribution in the cathode layer. In addition, positive ions generated by electron avalanche are mainly concentrated on the cathode layer, and mainly have O2 +Ion, O4 +Ion, N2 +Ions and N4 +Ion wherein O2 +The density of ions is the greatest. These positive ions eventually enhance the positive potential of the cathode layer. The cathode layer is a strongly ionized region in which positive ions are dominant and the plasma density is about 1015cm-3. The plasma density of the cathode layer is 3 orders of magnitude greater than the plasma density in the discharge development zone, thereby creating an electric field shield that reduces the electric field inside the generated discharge plasma to a very small value. However, the discharge development region has a strong reduced electric field, which is advantageous for the development of EHD force. The EHD force is mainly generated in the glow-like discharge phase of negative exposed electrode polarity. The source of EHD forces is the accumulation of the volume negative charge carried by long-lived oxygen anions. One source of EHD force is from attachment to O2O generated by electrons on the molecule2 -Ions. The cathode layer is the source of electrons, which can sustain the generation of negative ions. However, the positive ions in the cathode layer shield the applied voltage, affecting the electron emission. In addition, electrons emitted from the cathode layer are gathered on the surface of the medium (the whole negative polarity exposure electrode stage is continued), an external electric field is shielded, and the movement of oxygen anions to the surface is slowed down. At the same time, the average field strength of the cathode layer decreases, leading to cathode layer failure. After the cathode layer is destroyed, the electron source disappears and the development of EHD forces is limited. However, the positive ion cloud resulting from charge separation in the cathode layer remains exposed to electricityThe edges of the poles shield the applied voltage. The positive ion cloud continues throughout the negative polarity exposed electrode phase as electrons accumulate on the surface of the medium.
The cathode layer affects the mechanical performance of the actuator, however, its size is small, in the order of microns, and it is difficult to achieve experimental measurements.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a rapid and convenient experimental method for detecting cathode layers in surface dielectric barrier discharge, which utilizes a direct current power supply to provide scanning bias voltage, can realize comparison of cathode layer thicknesses generated by discharge of different exciters according to shielded bias voltage under the same bias voltage, and lays a foundation for subsequent experimental research of cathode layers.
The technical scheme of the utility model is as follows:
an experimental detection device for a cathode layer in surface dielectric barrier discharge comprises: the device comprises a surface dielectric barrier discharge plasma exciter, a direct current power supply, a potential probe, a high-voltage probe and a digital oscilloscope.
The surface dielectric barrier discharge plasma exciter comprises an exposed electrode, an insulating dielectric plate, a packaging electrode and an insulating adhesive tape; the upper surface of the insulating dielectric plate is fixed with the exposed electrode, and the lower surface of the insulating dielectric plate is fixed with the encapsulated electrode through an insulating adhesive tape.
The potential probe comprises a tungsten needle, a metal sheet and a metal rod; the tungsten needle is fixed on the metal sheet and connected with the metal rod.
The exposed electrode of the surface dielectric barrier discharge plasma exciter is connected with the high-voltage output end of the direct-current power supply through a constant-value resistor and is connected with a capacitor in parallel to protect the direct-current power supply.
A direct current voltage is used as a scanning bias voltage of the electric potential; the packaging electrode is connected with a driving power supply of the surface dielectric barrier discharge plasma exciter.
The potential probe is fixed on the numerical control displacement platform through an insulating bracket and is connected to the digital oscilloscope through the high-voltage probe; the digital oscilloscope selects a high resolution mode to directly record a time-averaged direct current component of the potential associated with surface charge accumulation, thereby filtering out an alternating current component;
the potential probe is placed 2mm-4mm above the edge of the exposed electrode, based on the principle that the probe tip produces a stable corona discharge.
The driving power supply adopts an alternating current power supply, the power supply frequency is 30kHz, and the voltage peak value is 12 kV;
the direct-current voltage of the direct-current power supply is-3 kV, -5kV and-7 kV; the direct current power supply is connected with an exposed electrode of the surface dielectric barrier discharge plasma exciter through a resistor; the plasma exciter exposed electrode is grounded through a capacitor.
The fixed value resistor is 100k omega and is arranged between the exposed electrode and the direct current power supply, so that the alternating current in the direct current circuit is limited to a lower level to ensure the safety of the direct current power supply.
The capacitance is 10 nF.
The potential probe can be a double-tungsten-needle potential probe, the diameter of the tungsten needle is 0.25mm, and the curvature radius of the tungsten needle is 0.01 mm; the distance between the two needles is 11 mm; the radius of curvature of the probe tip should be as small as possible to reduce interference of the probe with the dielectric barrier discharge plasma along the surface.
The high-voltage probe contains large internal resistance so as to play a role in dividing voltage in the potential measurement loop; the high-voltage probe with large fixed value resistance and small internal resistance can be used for replacing; the internal resistance of the high-voltage probe is 900M omega.
The digital oscilloscope adopts a high-resolution mode and aims to directly record a time-averaged direct-current component of electric potential related to surface charge accumulation and filter an alternating-current component.
The utility model has the beneficial effects that:
the utility model can quickly and conveniently realize the experimental detection of the cathode layer in the surface dielectric barrier discharge, the direct current power supply provides scanning bias voltage, the comparison of the thickness of the cathode layer is realized by comparing the shielding capacities of different exciters to the same bias voltage, the large gap of the cathode layer in the experimental comparison is filled, and the foundation is laid for the subsequent experimental research of the cathode layer.
Drawings
FIG. 1 is a diagram of an edge barrier discharge stimulator device with three different widths of exposed electrodes (a)3.2mm, (b)0.8mm, and (c)0.2mm, respectively;
FIG. 2 is a schematic diagram of a potential probe;
FIG. 3 is a comparison of cathode layer thickness in an in-plane barrier discharge;
FIG. 4 is a schematic diagram of the electrical connections along the surface of a barrier discharge device and a comparison of the cathode layer thickness;
FIG. 5 shows the distribution of surface potentials along the x-axis for different exposed electrode widths and different scanning bias voltages, where the exposed electrode widths are 3.2mm, 0.8mm, and 0.2mm, and the scanning bias voltages are 0kV, -3kV, -5kV, -7kV, respectively;
FIG. 6 shows the shielding voltage of the cathode layer under different scanning voltages and different widths of the exposed electrode, the widths of the exposed electrode are 3.2mm, 0.8mm and 0.2mm respectively, and the scanning bias voltages are 0kV, -3kV, -5kV and-7 kV respectively;
in the figure: 1 along the surface dielectric barrier discharge plasma exciter; 2 a copper electrode; 3 is an insulating medium plate; 4, insulating adhesive tape; 5, a tungsten needle; 6 a metal sheet; 7 a metal rod; 8, connecting points; 9 resistance; 10 a direct current power supply; 11 a capacitor; a 12-potential probe; 13 high voltage probe; 14, a digital oscilloscope; 15 an insulating support; 16 a numerical control displacement platform; 17 an alternating current power supply.
Detailed Description
The utility model is further described below with reference to the accompanying drawings.
The method for realizing the cathode layer thickness experiment detection device of different plasma exciters by adopting the device comprises the following steps:
firstly, selecting two or more surface dielectric barrier discharge plasma exciter devices to be compared according to a specific experiment; fig. 1 shows three different plasma actuators used in the experiment, differing only in the width of the exposed electrode, which was 3.2mm, 0.8mm and 0.2mm, respectively. The length of each electrode of the exciter is 70mm, the width of the encapsulated electrode is fixed to be 20mm, and the horizontal distance between the exposed electrode and the encapsulated electrode is 0 mm;
step two, connecting a circuit: as shown in FIG. 4, the exposed electrode along the surface dielectric barrier discharge exciter (a) in FIG. 1 is connected to the high voltage output terminal of a DC power supply 10 through a fixed value resistor 9 of 100k Ω, and is connected in parallel with a 10nF capacitor 11 to protect the DC power supply. A direct current voltage is used as a scanning bias voltage of the electric potential; the packaging electrode is connected with a driving power supply of the surface dielectric barrier discharge plasma exciter, the selection of the driving power supply can be determined according to experiment requirements, an alternating current power supply 17 is adopted as the driving power supply of the exciter in the experiment, the power supply frequency is 30kHz, and the voltage peak value is 12 kV;
thirdly, connecting a potential measuring system: the potential probe 12 is fixed on a numerical control displacement platform 16 through an insulating bracket 15 and is connected to a digital oscilloscope 14 through a high-voltage probe 13; the digital oscilloscope selects a high resolution mode to directly record a time-averaged direct current component of the potential associated with surface charge accumulation, thereby filtering out an alternating current component;
fourthly, adjusting the distance between the potential probe and the surface of the medium plate: firstly, placing a potential probe 12 about 2mm-4mm above the edge of an exposed electrode (the side where plasma is generated), starting an alternating current power supply and a direct current power supply, generating plasma on the surface of a dielectric plate, and finely adjusting the height of the potential probe through a numerical control displacement platform 16; in the experiment, the distance between the probe tip and the surface of the medium plate is 3.3 mm;
fifthly, adjusting a numerical control displacement platform to measure the distribution of the electric potential near the edge of the exposed electrode under different scanning bias voltages along the x axis, wherein the scanning bias voltages are respectively-3 kV, -5kV and-7 kV, and the electric potential probe scans from-2 mm to 18mm along the x axis in the experiment;
and sixthly, calculating the surface potential and the bias voltage shielded by the cathode layer:
calculating the surface potential U by an external loop series voltage division principle:
wherein U is1Voltage collected by the digital oscilloscope; r1900M Ω is the input resistance of the high voltage probe (PINTECH P6039A); r2Is the gap resistance between the probe tip and the exposed electrode, empirically about 50M Ω; therefore, it can be deduced that U ≈ 1.06U1；
Bias voltage U shielded by cathode layerShielding:
UShielding＝|UAC+UDC-UAC+DC|
And seventhly, replacing different plasma exciters, repeating the second step to the fifth step, and calculating the surface potential under the exciters and the bias voltage shielded by the cathode layer.
And eighthly, under the same bias voltage, comparing the magnitude of the bias voltage shielded by the cathode layers of different exciters, wherein the cathode layer of the exciter with the large shielded bias voltage is thicker.
Fig. 4 shows the distribution of surface potential along the x-axis for different exposed electrode widths and different scan bias voltages. We focus on the surface potential distribution within the electrode edge x-2 mm to x-2 mm. When a negative scan bias voltage is applied to the exposed electrodes, the surface potential near the electrodes drops, but by a significantly smaller amount than the value of the applied bias voltage, a phenomenon that is analyzed to be caused by a shielding effect produced by the cathode layer at the edges of the exposed electrodes.
In the alternating-current high-voltage surface dielectric barrier discharge, electrons in the cathode layer drift to the surface of the dielectric plate under the action of an electric field, and positive ions move to the electrode. When a negative scan bias voltage is applied to the exposed electrodes, the emission of electrons in the cathode layer is enhanced, resulting in an increase in the potential of the exposed electrode edge spaces. As shown in the negative scan voltage in fig. 4, the measured potential value in the vicinity of x ═ 0mm is larger than the value of the negative scan voltage. In addition, the electron emission of the cathode layer increases with an increase in the negative scan voltage, so that the potential difference between the potential of the exposed electrode edge and the applied scan voltage becomes more significant, and the shielding effect of the cathode layer against the scan voltage also increases.
Fig. 5 shows the voltages of the lower cathode layer shield at different scan voltages and different exposed electrode widths. It is known that, in the same scan voltage, plasma actuators having different electrode widths are exposed, and the generated cathode layer has different shielding voltages. As the width of the exposed electrode of the actuator increases, the voltage shielded by its cathode layer increases, indicating an increase in the thickness of the cathode layer.
In summary, it can be concluded that:
(1) the shielding effect of the cathode layer can be presented by applying a direct current scanning voltage on an exposed electrode of the surface dielectric barrier discharge plasma exciter;
(2) by comparing the shielding effect generated by different plasma actuators near the edges of the exposed electrodes, the thickness of the cathode layer thereof can be compared, the stronger the shielding effect, the thicker the cathode layer.
The utility model can realize the experimental detection of the cathode layer generated by the discharge of the plasma exciter and can realize the comparison of the thickness of the cathode layers of different exciters.
At present, the research of the cathode layer in the surface dielectric barrier discharge is only in a numerical simulation stage, and due to the thinner thickness and micron order, the thickness measurement of the cathode layer in the true sense cannot be realized in the experiment in the prior art, so the utility model is based on the experimental detection of the cathode layer and the comparison of the thickness of the cathode layer, and lays a foundation for the subsequent research.
The examples are only for showing the embodiments of the present invention, but not for limiting the scope of the patent of the present invention, it should be noted that, for those skilled in the art, many variations and modifications can be made without departing from the concept of the present invention, and these are all within the scope of the protection of the present invention.
Claims (6)
1. An experimental detection device for a cathode layer in surface Dielectric Barrier Discharge (DBD), comprising: the device comprises a surface dielectric barrier discharge plasma exciter (1), a direct current power supply (10), a potential probe (12), a high-voltage probe (13) and a digital oscilloscope (14);
the surface dielectric barrier discharge plasma exciter (1) comprises an exposed electrode (2), an insulating dielectric plate (3), a packaging electrode and an insulating adhesive tape (4); the exposed electrode (2) is fixed on the upper surface of the insulating dielectric plate (3), and the lower surface of the insulating dielectric plate (3) is fixedly packaged with the electrode through an insulating adhesive tape (4);
the potential probe (12) comprises a tungsten needle (5), a metal sheet (6) and a metal rod (7); a metal rod (7) is fixed on the upper surface of the metal sheet (6), and a tungsten needle (5) is fixed on the lower surface of the metal sheet (6) in parallel;
an exposed electrode (2) of the surface dielectric barrier discharge plasma exciter (1) is connected with a high-voltage output end of a direct-current power supply (10) through a constant value resistor (9) and is connected with a capacitor (11) in parallel to protect the direct-current power supply (10);
a DC power supply (10) as a potential scan bias voltage; the packaging electrode is connected with a driving power supply of the surface dielectric barrier discharge plasma exciter;
the potential probe (12) is fixed on a numerical control displacement platform (16) through an insulating support (15) and is connected to a digital oscilloscope (14) through a high-voltage probe (13); the digital oscilloscope (14) selects a high resolution mode to directly record a direct current component time-averaged with the surface charge accumulation potential, thereby filtering out an alternating current component;
the potential probe (12) is placed 2mm-4mm above the edge of the exposed electrode, based on the principle that the probe tip produces a stable corona discharge.
2. The apparatus for detecting cathode layer experiment in surface dielectric barrier discharge as claimed in claim 1, wherein said driving power source adopts an ac power source (17), the power frequency is 30kHz, and the peak-to-peak voltage is 12 kV.
3. The cathode layer experimental detection device in the planar dielectric barrier discharge as claimed in claim 1 or 2, wherein the dc voltage of the dc power supply (10) is-3 kV, -5kV and-7 kV; the direct current power supply is connected with an exposed electrode (2) of the surface dielectric barrier discharge plasma exciter through a resistor; the exposed electrode (2) of the plasma exciter is grounded through a capacitor.
4. The cathode layer experimental detection device in the planar dielectric barrier discharge as claimed in claim 1 or 2, wherein the fixed resistor (9) is 100k Ω, and is disposed between the exposed electrode (2) and the dc power supply for limiting the ac current in the dc circuit to a low level to ensure the safety of the dc power supply.
5. The cathode layer experimental detection device in the surface dielectric barrier discharge as claimed in claim 1 or 2, wherein the potential probe (12) can be a double tungsten needle potential probe, the diameter of the tungsten needle (5) is 0.25mm, and the curvature radius is 0.01 mm; the distance between the two needles is 11 mm; the radius of curvature of the probe tip should be as small as possible to reduce interference of the probe with the dielectric barrier discharge plasma along the surface.
6. The cathode layer experimental detection device in the surface dielectric barrier discharge as claimed in claim 1 or 2, wherein said high voltage probe (13) has a large internal resistance to function as a voltage divider in a potential measurement loop; the high-voltage probe with large fixed value resistance and small internal resistance can be used for replacing; the internal resistance of the high-voltage probe (13) is 900M omega.
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