JP5360800B2 - Surface plasma generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface plasma generation device for stably generating high-speed surface plasma by properly setting the rising speed of voltage to be applied between electrodes. <P>SOLUTION: The surface plasma generation device includes the surface side electrode and the back side electrode with an insulting material therebetween, wherein a voltage is applied between both electrodes to generate surface plasma. The rising speed of the voltage to be applied between the electrodes is 3-7 &mu;s/kV, preferably 4-5 &mu;s/kV. Preferably, this applied voltage is pulsed to set the rising speed of the applied voltage to be a predetermined value. It can be triangle-waveformed to rise at the predetermined value. At this point, the waveform lowering on the negative side can be set to be smaller. Additionally, when the surface side electrode is doughnut-shaped, surface plasma jet rises vertically from the surface, and so the rising speed of the applied voltage is easily and properly set. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a surface plasma generator that generates plasma along the surface of an insulator by applying a high-voltage, high-frequency current to electrodes provided on both the front and back sides of the insulator, and in particular, the rising of the applied high-frequency current. The present invention relates to a surface plasma generator capable of generating high-efficiency and high-speed plasma by appropriately setting the voltage speed.

  Various actuators have been developed so far, but in recent years, actuators using surface plasma have attracted attention. For example, as shown in FIG. 7A, the surface plasma actuator is provided with a front-side electrode 72 and a back-side electrode 73 with an insulator 71 made of resin, ceramic or the like interposed therebetween, and an AC electric field is generated by an AC power source 74 on both electrodes. Then, the fact that a plasma jet 76 as surface plasma is generated from the edge 75 of the surface-side electrode 72 along the surface of the insulator 71 is utilized. Such surface plasma is also called a DBD (dielectric barrier discharge) plasma actuator. In particular, since such surface plasma induces ambient gas and generates an induced airflow 77, studies have been made to effectively use this action.

In particular, as shown in FIG. 7A, the AC power supply 74 can be controlled by the control device 80, and the gas velocity and temperature are detected by the sensor 81, or the actual electrode applied voltage is detected and controlled by the signal. The device 80 can control the AC power source 74. Voltage from the AC power supply applied to the electrode at this time is, for example, a sine wave as shown in FIG. 7 (b), walk outputs AC pulse wave having a predetermined narrow width, as shown in FIG. 7 (c) . When trying to generate a stronger plasma jet from such a controlled state, it can be dealt with by performing duty ratio control that increases the frequency in the case of a sine wave and increases the supply time in the case of a pulse wave. .

  The application of surface plasma to various applications is currently under study, and research is being conducted on the use of airflow from the blades due to the generation of eddy currents in airplanes, windmill blades, turbine blades, and the like. The characteristics of surface plasma are further clarified in the course of research on such actuators, and this surface plasma actuator can generate a specific plasma jet depending on the shape and arrangement of electrodes, In addition, it has become clear that it can be used as a wider range of actuators.

That is, it is possible to generate a variety of plasma jet by the arrangement and shape of the surface side electrodes for generating surface plasmon, the parallel with intervals to each other in the surface of the insulator 91, for example, as FIG. 8 (a) (b) When the first surface side electrode 92 and the second surface side electrode 93 are arranged to face each other and a high electric field is generated between the back surface side electrode 94 provided on the back surface, the arrangement relationship between the front surface side electrode and the back surface side electrode Then, surface plasma similar to the above is generated in parallel to the surface from the edge of each surface side electrode facing each other. These plasma jets collide at the middle part of each electrode, and as shown in FIG. 8B, a plasma jet 95 rising from the surface of the insulator 91 is formed. At that time, an induced air flow 96 is generated in which the surrounding gas is guided substantially perpendicularly to the surface as shown in the figure.

To form a surface side electrode 98 as shown in other example FIG. 9 (a), the donut-shaped with a central opening 97, or a rectangle with a circular central opening 97 as shown in FIG. 9 (b), 9 (c), the by the generating high electric fields, the arrangement of the surface side electrode 98 and the back-side electrode 102 relationship between the back-side electrode 10 2 which is provided on the back surface of the insulator 99, the surface-side electrode 98 Surface plasma 103 is generated parallel to the surface from the edge on the side of the central opening 97 toward the center. The surface plasmas 103 collide with each other at the center, and a plasma jet 100 rising from the surface is formed. In addition, an induced airflow 101 is generated at a right angle to the surface by being induced by the plasma jet 100.

  As described above, various plasma jets can be generated depending on the shape and arrangement of the electrodes, and this can be used as various actuators in addition to performing the anti-separation action by controlling the vortex generation of the blade as described above. Can be considered.

The plasma actuator is described in detail in the following document.
Roth, JR, Sherman, DM, and Wilkinson, SP (1998) .Boundary layer flow control with a one atmosphere uniform glow discharge.AIAA Paper 98-0328, 36th Aerospace Sciences Meeting and Exhibit, Reno, Nevada. Corke, TC, Jumper, EJ, Post, ML, Orlov, D., and McLaughlin, TE (2002) .Application of weakly-ionized plasmas as wing flow-control devices.AIAA paper 2002-0350, 40th Aerospace Sciences Meeting & Exhibit , Reno, Nevada. Santhanakrishnan, A. and Jacob, JD (2006) .On plasma synthetic jet actuators.AIAA paper 2006-0317, 44th Aerospace Sciences Meeting, Reno, Nevada.

In the plasma actuator using the surface plasma as described above, various plasmas can be generated as described above and can be applied to various applications. However, this plasma can be used more efficiently and at high speed. in studying developed a method of generating is the most basic this when used widely this surface plasma generator. For this reason, research has been conducted to generate higher-speed surface plasma while studying the generation characteristics of surface plasma in detail. However, according to the research results to date, effective methods have not yet been developed. Further, in recent years, how to generate DBD plasma at a low voltage has become a big problem, but it cannot be said that a sufficient method has been developed at present.

  Therefore, a main object of the present invention is to provide a surface plasma generator capable of stably generating a high-speed surface plasma at a low voltage.

  The present inventors have conducted many experiments on the surface plasma actuator, also referred to as a DBD (dielectric barrier discharge) plasma actuator as described above, and as a result of repeated research, the inventors have studied the surface plasma by varying the mode of current applied to the electrodes. It is systematically revealed that the generation mode, in particular, the plasma velocity changes, and it is not possible to clearly grasp by simply observing the state of the plasma generated parallel to the surface as shown in FIG. In particular, various experiments were attempted focusing on the fact that when plasma is generated by a donut-shaped electrode as shown in FIG. 9, the degree of plasma generation can be observed in the state of plasma rising vertically from the surface.

  Furthermore, in order to clearly grasp the state of the surface plasma rising vertically in this way, the velocity of each visualized particle is measured by visualizing the plasma with a laser and supplying the visualized particles around the test section. We thought to observe the behavior of the surface plasma rising vertically. FIG. 3 shows an apparatus manufactured for an actual experiment. In the experimental apparatus shown in FIG. 9, as shown in FIG. 9 (d), an electrode pattern made of a copper foil of about 35 μm is adhered to both surfaces of an insulator made of polyester having a thickness of 130 μm, and the surface side electrode is etched. Is formed in a donut shape having an inner diameter di of 50 mm and a width of 10 mm, and the back side electrode is formed in a circular shape having the same diameter and the same outer periphery as the inner diameter of the donut shape.

  Using such a donut-shaped electrode, it was set on the bottom surface in an acrylic transparent container C as shown in FIG. 3, and a voltage having a predetermined waveform was applied by a signal generator HV-RF. In many cases, a normal surface plasma is observed by using a sine wave as shown in FIG. 7B. In this case, when investigating the frequency dependence of the plasma generation speed, the input frequency (fp) Since the voltage rising speed (dV / dt) also changes with the change, it is necessary to discuss the influence on the plasma jet generation speed from both aspects.

  On the other hand, if the applied voltage waveform is a rectangular wave, if dV / dt can be made constant, it is possible to directly investigate the dependency of the plasma jet velocity on the input frequency (fp), or conversely, the dependency of the applied voltage waveform. Become. Therefore, the experimental apparatus shown in FIG. 3 generates a pulse wave as shown in FIG. In this pulse wave example, the amplitude is ± 3.5 kV, the frequency Fp can be changed to 2.5, 5.0, 7.5, 10.0 kH, and the width Tb of a series of applied voltage waveforms is 0.1 sec. In this example, the time interval Tr where a series of applied voltage waveforms is generated, that is, 1 / fr is 2.0 sec, and the time interval Ts of the series of applied voltage waveforms is 1.9 sec.

  However, although this pulse wave appears to be a rectangular wave, it is a general trapezoidal wave as is apparent from FIG. The inventors consider the dependence of the plasma jet velocity on the applied voltage waveform, in particular, to observe this trapezoidal wave by changing the rising speed dV / dt of the applied voltage, that is, changing the speed of the rising portion of the waveform. As shown in FIG. 2C, the rising speed of the voltage is controlled by changing the rising speed of the applied voltage from a to b, c, d, e, f, g, and h as shown in the waveform schematic diagram in FIG. A waveform in which the rising speed dV / dt of the applied voltage changes was formed and applied.

  In the experimental apparatus shown in FIG. 3, the plasma jet rising from the center of the donut-shaped electrode by the applied voltage as described above is visualized by irradiating a laser generated by a double pulse YAG laser from the outside of the container C. Further, propylene glycol atomized to several μm is used as the visualization particle, and is supplied into the container C by the air compressor D. Since the atomized propylene glycol is heavier than air, the propylene glycol can stay around the plasma generator installed in the lower part of the atmospheric container C for a certain period of time. By supplying such visualization particles, the plasma jet can be clearly visualized by the laser irradiated as described above. Further, by measuring the behavior of the visualized particles, it is possible to measure the direction and velocity of each part of the plasma jet and the airflow around it. In the measurement, a portion visualized with a laser beam by a digital video camera shown as a CCD camera is photographed at intervals of about 0.04 seconds from a direction perpendicular to the laser beam.

As a result of observing the state of generation of the plasma jet and analyzing the velocity at each part by observation with this experimental apparatus, for example , the voltage rising speed shown in d of FIG. 2 is a velocity line as shown in FIG. A figure was obtained. In the figure, arrows in the screen indicate the direction and size of the airflow. In the figure, images shown in black and white are actually colored and displayed according to the magnitude of the speed, and are shown as red, yellow, green, and blue in the figure. As a result, the velocity distribution around the plasma jet and its surroundings can be seen at first glance. In particular, vortices are generated on both sides of the vertically rising plasma jet, and the height hv of the vortex center (see FIG. 1 (b)). ) were found to be directly related to the magnitude of the air flow of the plasma jet. vortex center height hv in the example shown in FIG. 4 is a substantially 42mm, the variable resistance value R = 80 (Fig. as described later 2 (c)) , the rising speed dV / dt of the applied voltage is the largest plasma jet velocity, and the velocity of the plasma jet decreases even if it is larger or smaller than that. As a result, the present invention has been achieved.

More specifically, the present invention as described above is as follows. That is, in order to solve the above problems, the surface plasma generator according to the present invention is provided with a surface side electrode and a back surface side electrode with an insulating material interposed therebetween, and an AC voltage from an AC power source is applied between both electrodes. In a surface plasma generator that generates plasma, the pulse waveform of the voltage applied to the electrode is a triangular wave that rises linearly until reaching the maximum voltage, and a similar waveform on the negative side that follows the waveform. For a triangular wave that rises up to the maximum voltage, the triangular wave that rises up to the maximum voltage has a time required to increase by 1 kV, that is, the reciprocal of the voltage rising speed is in the range of 4 μs / kV to 5 μs / kV. The triangular wave falling to the minus side while having a predetermined value is characterized in that it has a shorter time than the rising triangular wave .

  According to the present invention as described above, by setting the rising speed of the applied voltage to an appropriate value, it is possible to stably generate a high-speed surface plasma at a low voltage.

The present invention provides a problem that a high-speed surface plasma can be stably generated by providing a surface-side electrode and a back-side electrode with an insulating material interposed therebetween, and applying a voltage between the two surfaces. In a surface plasma generator for generating plasma, the voltage applied to the electrode is increased linearly in a trapezoidal waveform until reaching the maximum voltage, and the time required to increase by 1 kv, that is, the reciprocal of the voltage rising speed Is realized by setting a predetermined value in the range of 4 μs / kV to 5 μs / kV .

  Embodiments of the present invention will be described with reference to the drawings. In the present invention, as described above, the experimental apparatus shown in FIG. 3 is used to measure the relation of the change in the speed of the plasma jet flow generated by changing the rising speed of the applied voltage. The rising speed of the applied voltage at that time is measured. As shown in FIG. 2C, the change is made by changing the voltage from a to b, c, d, e :, f, g, h by the rising voltage control as shown in FIG. As shown in the figure, a waveform in which the rising speed dV / dt of the applied voltage changes is formed and applied. Such rising speed of the applied voltage is also shown in another manner in FIG. That is, in the example shown in FIG. 1, a pulsed applied voltage as shown in FIG. 1C is applied to a surface plasma jet generator using a donut-shaped surface electrode as shown in FIG. Shall. As shown in FIG. 1 (d) showing a part of the pulse-like applied voltage in an enlarged manner, this applied voltage has a rectangular wave shape, and the rising speed of the applied voltage of this waveform is as shown in FIG. 2 (c). A pulse voltage changed to is applied. As a result, as shown in FIG. 1E, the time from the pulse application time t = 0 to the rise to 1 kV was changed as a to h.

As a result, data as shown in FIG. 4 was obtained by the experimental apparatus for each. These are summarized as ah in FIG. 5A to 5H correspond to voltage rise rate change examples a to h shown in FIG. 1E, respectively. In this figure, the vortex center position is shown on the left side of each figure, and the vortex center height generated at the voltage rising speed of d is shown in all the figures, and the vortex center height in each condition is shown. Making the comparison easier. In addition, these figures each show an average value obtained by performing the experiment 50 times. As is clear from this figure, the vortex center height is the highest when (dV / dt) ⁻¹ = 4 μsec / kV, which is the reciprocal of the voltage rise rate of d, and is the reciprocal of the voltage rise rate of e ( dV / dt) ⁻¹ = 5 μsec / kV, the height of the vortex center is substantially the same, and therefore all others are low. From this, it is the reciprocal of the voltage rise rate (dV / dt) ^−1. = 4 μsec / kV or (dV / dt) ⁻¹ = 5 μsec / kV It was found that the rising speed dV / dt of the applied voltage was the fastest plasma jet.

  A graph of this is shown in FIG. That is, FIG. 1A shows a change in the rising speed of the applied voltage shown in FIG. 1E, that is, a change in the rising speed of the applied voltage corresponding to FIGS. 5A to 5H. Further, the results of many similar experiments are summarized and graphed.

As is apparent from this figure, when expressed as the reciprocal of the rising speed of the applied voltage , that is , the time to rise to the predetermined voltage [μs / kV], an effective annular jet height in the range of 3 to 7 μs / kV. is (hv) Ri see that mm is obtained, in particular, it can be seen that a particularly suitable range is in the range of 4~5μs / kV. According to the present invention, when the DBD plasma generator is set within such a range, it can be seen that a predetermined flow rate can be obtained even at a low voltage regardless of the voltage. Conversely, even if the voltage or frequency is increased, it is suggested that the flow rate decreases if there is no change in the rising speed of the applied voltage close to the optimum condition.

Although it has been found that the reciprocal of the rising speed of the applied voltage as described above is in a particularly suitable range, the applied voltage at that time is as shown in FIG. 6A in addition to the trapezoidal pulse as described above. and a triangular waveform. That is, in the example shown in FIG. 6A, the reciprocal of the rising speed of the applied voltage is set to 4 μs / kV which is an optimum value, and when it reaches Va (kV) which is a predetermined voltage, it falls to 0 kV. A similar waveform is generated on the − side, and thereafter, the + and − waveforms are continuously supplied as one cycle. At this time, the triangular wave is 4Va × 10 ⁻⁶ and repeats to the plus and minus sides. When V = 3 (kV), fp (max) is approximately 41 kHz. The maximum efficiency is estimated to be 125,000 / EHz for fp. This also means that the maximum voltage can be lowered by increasing the frequency.

Further, as in FIG. 6 (b), has the inverse of the rising speed of the applied voltage and the 4 .mu.s / kV, falls until 0kV at a predetermined voltage V (kV), next - a short time similar waveform to the side Only after that, these waveforms are continuously supplied as one period. At this time, since the amount of driving on the minus side is reduced, the maximum efficiency can be 250,000 / VaHz, which is almost twice the efficiency of the example of FIG.

  As described above, in the present invention, as a result of many experiments by the inventors, it has been estimated that the rising speed of the voltage applied to the electrode has an optimum range centered on the optimum value. It is not appropriate to use plasma along the surface. In particular, it is easy to observe and visualize the state of the plasma jet velocity when the plasma generated using a donut-shaped electrode is raised vertically from the surface. In the observation of the generated plasma jet, it was found that the height of the center of the vortex is directly related to the velocity of the plasma jet, especially in the state of vortex generation. Inappropriate and adopting a method to change the rising speed of the applied voltage for this pulse wave, and the change and the height of the vortex center By measuring the relationship between changes in the surface voltage, the surface plasma jet velocity reaches its maximum value at a specific value of the rising speed of the applied voltage, and a particularly effective range exists within a predetermined width. Thus, the present invention has been achieved.

Therefore, the present invention does not need to be a donut-shaped surface plasma generator, and it is apparent that the present invention can be provided for a conventionally proposed electrode-shaped surface plasma generator. Also, Ru der those found properties of the surface plasma generated by the pulse waves as described above.

It is a figure which shows the Example of this invention, (a) is a figure which shows the rising speed optimal range of the applied voltage for surface plasma generation, (b) is a donut type used in order to observe the speed of a surface plasma jet It is an example of the surface plasma generator provided with the electrode, (c) shows the example of the voltage waveform applied to this surface plasma generation electrode, (d) is a partially enlarged view of the waveform, (e) Is a diagram showing an example of change in rising speed of the applied voltage, in which a to h correspond to the indicated points of (a). It is a figure which shows the example of an electrode applied voltage, (a) is a figure which shows the whole applied voltage pulse, (b) is the one part enlarged view of the applied voltage, (c) is a variable resistance FIG. 6 is a waveform schematic diagram showing changes in the variable resistance and applied voltage when changing in FIG. It is an example of the experimental apparatus which measures the relationship between the rising speed of an applied voltage, and a plasma jet velocity. FIG. 3 is a velocity distribution diagram showing an example where d is the direction and velocity of each part of a plasma jet that rises vertically from the surface obtained by the experimental apparatus. It is a figure which shows the velocity diagram similar to FIG. 4, respectively when changing the rising speed of the applied voltage obtained with the same experimental device. It is a figure which shows the example of a triangular wave-like applied voltage waveform in the state which optimized the rising speed of the applied voltage, (a) is an example which formed the same waveform on the plus and minus side, (b) is small on the minus side. It is a figure which shows the example which formed the waveform. (A) is a figure which shows the example of the generator of surface plasma, (b) is a wave form diagram when the applied voltage to an electrode is a sine wave, (c) is a pulse wave when the applied voltage to an electrode is a pulse wave. It is a wave form diagram when it is. It is a figure which shows the example of the surface plasma generator provided with the surface electrode which formed the parallel edge mutually opposed conventionally proposed. It is a figure which shows the example of the surface plasma generator provided with the donut type surface electrode proposed conventionally.

Claims (2)

In the surface plasma generator for generating the surface plasma by providing the surface side electrode and the back side electrode across the insulating material and applying the AC voltage from the AC power source between both electrodes,
The pulse waveform of the voltage applied to the electrode is a triangular waveform that rises linearly until reaching the maximum voltage, and a waveform consisting of a triangular waveform that falls in a similar waveform on the negative side continuous with the waveform, For the triangular wave that rises up to the maximum voltage, the time required to rise by 1 kV, that is, the reciprocal of the voltage rise speed is set to a predetermined value in the range of 4 μs / kV to 5 μs / kV, and rises to the minus side. The descending triangular wave has a shorter time than the rising triangular wave .   2. The surface plasma generation apparatus according to claim 1, wherein the surface side electrode has a donut shape.