KR20210152653A - Noise sound absorbing device using a plasma actuator - Google Patents

Abstract

The present invention relates to a noiseless sound-absorbing apparatus using a plasma actuator. More specifically, the present invention relates to the noiseless sound-absorbing apparatus using the plasma actuator, which induces sound absorption by attaching the plasma actuator to the inside of a three-dimensional object rotated by a circle by discharging a noise transmitted from the outside to the inside to the outside of the three-dimensional object. The noiseless sound-absorbing apparatus using the plasma actuator of the present invention comprises: the three-dimensional stereoscopic shape unit; and the plasma actuator.

Description

Noise sound absorbing device using a plasma actuator

The present invention relates to a noiseless sound absorbing device using a plasma actuator, and more particularly, by attaching a plasma actuator to the inside of a three-dimensional object rotated by a circle by an axis, the noise transmitted from the outside to the inside is discharged to the outside of the three-dimensional object to absorb sound It relates to a silent sound absorbing device using an inducing plasma actuator.

Basically, sound (noise) is a wave propagating while vibrating with high and low pressure in a medium. The removal of sound (noise) consists in dissipating the pressure, and a representative example of this is pressure dissipation through external wind. It can block all sounds, unlike a resonator that removes sound (noise) of a specific frequency.

On the other hand, plasma refers to a state in which ionized gas having a local electrical polarity exists, and is called the fourth state because it is distinguished from solid, liquid, and gaseous states.

Plasma observed in natural phenomena includes lightning, aurora, and the sun, and in an artificial way, plasma can be generated through discharge.

Depending on the type and characteristics of the discharge, various plasmas can be generated. There are vacuum and atmospheric plasmas depending on the pressure conditions, and there are direct current (DC), alternating current (AC), RF, and microwave plasmas depending on the type of power supply.

Plasma with high gas and electron temperatures, such as arc, is classified as high-temperature plasma, and low-gas temperature but high electron temperature, such as glow discharge, is classified as low-temperature plasma.

The basic principle of the plasma flow control is that when plasma is generated, positive ions accelerate in the direction of the electric field and electrons accelerate in the opposite direction of the electric field.

At this time, electrons drift while colliding with neutral particles, thereby causing a current to flow in the plasma. In this electric field drift, the momentum of the flow can be changed by using the momentum of ions having a charge e.

That is, when plasma is generated, a body force is generated due to collision between ions moving between electrodes and air molecules, and the resulting flow is referred to as “electric wind” or “ionic wind”. wind)".

Using such electric wind, it can be used for boundary layer transition delay, vortex generation, and surface friction reduction. In general, an electric wind generator using the principle of such a plasma is called a "plasma actuator".

Meanwhile, a device for effectively reducing ambient noise is an important consideration in everyday life or industrial sites.

The sound absorption method used in many industrial sites to reduce noise generated from various mechanical equipment, etc. can be divided into porous type, resonance type and plate type sound absorption method according to the principle.

The porous sound absorption method is a method to improve the sound absorption rate at a specific frequency and broadband frequency by adopting an appropriate material with high sound absorption performance, and the resonance type and plate type sound absorption method partially reduces the sound absorption rate at a specific frequency by modifying the internal structure of the sound absorption material. way to improve it.

Existing sound absorption technologies have a clear limitation that a high sound absorption coefficient cannot be expected at low frequencies only with a thin sound absorption material thickness, and also, when noise of multiple frequencies occurs, high sound absorption performance cannot be selectively expected for each frequency.

Accordingly, there is a need for a sound absorbing technology that allows a designer to select two or more frequencies and can design a sound absorbing device that occupies only a small space.

Korean Patent Publication No. 2015-0085954 US Patent No. 5387842

The present invention has been made to solve the above problems, and the sound wave passes through the plasma layer through a three-dimensional shape in which a space including an air inlet and an air outlet is formed, energy is reduced and sound is absorbed using a plasma actuator. An object of the present invention is to provide a sound absorbing device.

Also, according to the present invention, a new out of phase type of vibration or a phase cancellation for a specific frequency can be generated for each frequency.

In order to solve the above problems, the present invention includes: a three-dimensional three-dimensional shape including a three-dimensional space in which an inlet for introducing air therein and an outlet for receiving and discharging the air are formed, the air flows therein; Plasma actuators installed at regular intervals in the inlet portion or the outlet portion along the inner surface of the three-dimensional shape portion; including, the plasma actuator, a first electrode; a second electrode vertically spaced apart from the first electrode at a predetermined distance and disposed parallel to a surface of the first electrode; and a dielectric formed between the first electrode and the second electrode.

In the present invention, a sound wave proceeds in the central portion of a donut shape having a hollow opening and a hollow shape, and an inlet portion for penetrating and entering the inner space toward the donut shape inner surface, and the sound wave rotates inside the donut shape ( a three-dimensional donut-shaped part including a moving three-dimensional space part and a discharge part for allowing sound waves that rotate and flow in the three-dimensional space part to be discharged toward an outer surface of the donut shape; Plasma actuators installed at regular intervals in the inlet portion or the outlet portion along the inner surface of the three-dimensional shape portion; including, the plasma actuator, a first electrode; a second electrode vertically spaced apart from the first electrode at a predetermined distance and disposed parallel to a surface of the first electrode; and a dielectric formed between the first electrode and the second electrode.

The plasma actuator may include an alternating current (AC) electrically connected to the first electrode and the second electrode; The AC unit divides the full-wave rectified voltage waveform obtained through the rectification bridge diode with a high-frequency capacitor and then is connected to a half-bridge converter that obtains an output voltage waveform identical to the input voltage through a half-bridge converter circuit to supply an AC voltage.

The plasma actuator is a DBD (Dielectric Barrier Discharge) plasma actuator, wherein the first electrode installed on the dielectric is an exposed electrode installed in a state exposed to the inner space, and the second electrode is the electrode installed under the dielectric is air and It is a submerged electrode installed by blocking the contact of

The virtual contact portion where the exposed electrode and the submerged electrode virtually meet is one of a rectangular arrangement, a sawtooth arrangement, or a wavy arrangement.

By adjusting the intensity and frequency of the voltage to the plasma actuator, the collision rate between the plasma moving in a certain direction and the medium particle (air particle) of the neutral sound wave is increased to a certain value or more to control sound absorption.

The electrical parameters of the plasma actuator change voltage and frequency, or the shape of a waveform, the dielectric parameters change thickness or material, or the electrode parameters change one of the electrode thickness, size, or material type. do.

The half-bridge converter may include: a first resonant capacitor and a second resonant capacitor connected in series with each other; a first switch and a second switch connected in series with each other, wherein one end of the primary side of the transformer is connected in parallel between the first resonant capacitor and the second resonant capacitor, and the other end of the primary side of the transformer is the first switch and a parallel connection between the second switch.

The present invention made as described above Since the plasma actuator has less vibration or noise than any other mechanical means, it can be easily used in a noiseless sound absorbing device.

In addition, the present invention can facilitate the process of introducing and discharging air through the donut shape, so that the sound absorption effect according to the simple structure is very large.

1 is a cross-sectional view of a noise-free sound absorbing device using a plasma actuator according to the present invention and a view showing a process of introducing and discharging air therein.
2 is a view showing a process of absorbing sound through six inlet and outlet using a noiseless sound absorbing device using a plasma actuator according to an embodiment of the present invention.
3 is a view showing a form having eight inlet and outlet in a noiseless sound absorbing device using a plasma actuator according to another embodiment of the present invention.
4 is a view showing a form having a plurality of inlet and outlet in a noiseless sound absorbing device using a plasma actuator made according to another embodiment of the present invention.
5 is a view showing a plasma actuator when a virtual contact surface made according to another embodiment of the present invention is a straight line.
6 is a view showing a plasma actuator when the virtual contact surface made according to another embodiment of the present invention has a sawtooth shape.
7 is a diagram illustrating a half-bridge converter circuit according to an embodiment of the present invention.
8 and 9 are diagrams showing the actual appearance of FIGS. 5 and 6 , respectively.
10 is a view showing an actual appearance of a half-bridge converter according to an embodiment of the present invention.

In order to fully understand the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. This example is provided to more completely explain the present invention to those of ordinary skill in the art. Accordingly, the shapes of elements in the drawings may be exaggerated to emphasize a clearer description. It should be noted that the same members in each drawing are sometimes shown with the same reference numerals. In addition, detailed descriptions of well-known functions and configurations determined to unnecessarily obscure the gist of the present invention will be omitted.

As shown in FIG. 1, the present invention includes a three-dimensional three-dimensional shape part 100 made of a donut shape, etc., four plasma actuators 101, four inlet parts 103, and four outlet parts 102. .

The three-dimensional three-dimensional shape part 100 includes a three-dimensional space part in which an inlet part for introducing air and an outlet part 102 for receiving and discharging the air are formed therein, and the air flows therein.

The three-dimensional three-dimensional shape part 100 is an inlet part 103 that penetrates into the inner space toward the donut-shaped inner surface while the sound wave proceeds from the central portion of the donut shape having a hollow opening in the center, and the sound wave A three-dimensional donut shape comprising: a three-dimensional space part rotationally flowing inside the donut shape; is wealth

The plasma actuator 101 is installed at regular intervals in the inlet or outlet 102 along the inner surface of the three-dimensional shape.

For example, when the sound wave S is incident in the tangential direction of the interior hole of the three-dimensional shape, a plurality of plasma actuators 101 may be arranged on a plane perpendicular to the incident sound wave.

As shown in FIG. 2 , six inlet portions 103 are generated on the side of the donut-shaped inner space, and six discharge portions 102 corresponding to the six inlet portions 103 are formed on the donut-shaped outer surface. It is created by penetrating the inner space.

As shown in FIG. 3 , the eight outlets 102 corresponding to the eight inlet 103 are installed at regular intervals in the inlet or outlet 102 along the inner surface of the three-dimensional shape. is generated toward the outside through the inner space on the donut-shaped outer surface.

This method is equally applied to the plurality of discharge units 102 corresponding to the plurality of inlet units 103 as shown in FIG. 4 , and the sound waves entering the plurality of inlet units 103 are generated by the plasma actuator 101 . The wavelength and phase of the electric wind are different, causing destructive interference.

5 and 6, the plasma actuator 101 has a flat plate-type first electrode 101-1, and is vertically spaced apart from the first electrode at a predetermined distance, and the surface of the first electrode and the It includes a second flat electrode 101 - 2 spaced apart and disposed in parallel and a dielectric formed between the first electrode and the second electrode.

The first electrode and the second electrode are formed in a plate shape having a flat predetermined length so as to face each other and be disposed in parallel, and the first electrode and the second electrode are electrically connected to the AC unit AC.

In one embodiment, the plasma actuator 101 is a DBD (Dielectric Barrier Discharge) plasma actuator, wherein the first electrode installed on the dielectric is an exposed electrode installed in a state exposed to the internal space, and the second electrode is the dielectric As the electrode installed at the lower part, a submerged electrode installed by blocking contact with air may be used.

The virtual contact portion (in a plan view) where the exposed electrode and the submerged electrode virtually meet is one of a rectangular arrangement, a sawtooth arrangement, or a wavy arrangement, and is formed between at least two or more electrode layers that are vertically spaced apart from each other and arranged in parallel spaced apart by a dielectric layer.

By adjusting the intensity and frequency of the voltage to the plasma actuator 101, the collision rate between the plasma moving in a certain direction and the medium particles (air particles) of the neutral sound wave is increased to a certain value or more, thereby controlling sound absorption.

The electrical parameters of the plasma actuator 101 are to change the voltage and frequency, or the shape of the waveform, the dielectric parameters change the thickness or material, or the electrode parameters are one of the electrode thickness, size, or material. is to change

In addition, as the thickness of the electrode of the plasma actuator 101 becomes thinner, a faster air flow velocity distribution can be exhibited and flow can be made over a wider area.

The electrons generated in the plasma drift while colliding with the neutral particles so that a current flows in the plasma. In this electric field drift, the momentum of the flow can be changed by using the momentum of the ion having the charge e.

As an embodiment of the present invention, one electrode of the plasma actuator 101 is exposed to the air, the other electrode is inserted into the dielectric to be asymmetrically arranged, and AC power of several tens of kV is supplied, and the dielectric is inserted and insulated. In order to generate plasma above the electrode and facilitate flow in the direction of the insulated electrode from the exposed electrode, the dielectric is made of polymethyl methacrylate (PMMA) and polyacrylonitrile; One of polyacrylic acid may be used.

In another embodiment of the present invention, the composition of the dielectric has a perovskite crystal structure containing at least Bi, Na, Sr and Ti, and La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy , Ho, Yb, Ba, Ca, contains at least one selected from Mg and Zn.

Specifically, the dielectric composition having a perovskite crystal structure is a _{polycrystalline material including a perovskite compound represented by the general formula ABO 3} as a main phase, wherein A is Bi, Na, and Sr. at least one, and B includes at least Ti.

When the total of A is taken as 100 wt%, it is preferable that the proportion of Bi, Na and Sr contained in A is at least 80 wt% in total.

Moreover, if the total of B is taken as 100% by weight, it is preferable that the proportion of Ti contained in B is at least 80% by weight.

The plasma actuator 101 divides a full-wave rectified voltage waveform obtained from a commercial AC voltage source through a rectifying bridge diode with a high-frequency capacitor, and then connects to a half-bridge converter to obtain an output voltage waveform equal to the input voltage through a half-bridge converter circuit to be supplied with voltage.

7 and 10, the half-bridge converter includes a first voltage 201 (V1) and a second voltage 202; V2 connected in series with each other, a first switch 211; S1 and a second voltage connected in series with each other. 2 includes a transformer 220 connected to the switch 212 (S2).

A first resonant capacitor C1 and a second resonant capacitor C2 connected in series to each other as an embodiment, and a first switch S1 and a second switch S2 connected in series to each other, One end of the primary side is connected in parallel between the first resonant capacitor C1 and the second resonant capacitor C2, and the other end of the primary side of the transformer is connected between the first switch S1 and the second switch S2. A parallel-connected converter can also be used.

100: three-dimensional three-dimensional shape part
101: plasma actuator
101-1: first electrode
101-2: second electrode
102: discharge part
103: inlet
200: AC unit
201, 202, V1, V2: Voltage
211, 212, S1, S2: switch
220: transformer
AC: AC part
C1, C2: capacitor

Claims (8)

a three-dimensional three-dimensional shape portion including a three-dimensional space portion in which an inlet for introducing air and an outlet for receiving and discharging the air are formed, the air flows therein;
Plasma actuators installed at regular intervals in the inlet or outlet along the inner surface of the three-dimensional shape.
The plasma actuator is
a first electrode;
a second electrode vertically spaced apart from the first electrode at a predetermined distance and disposed parallel to a surface of the first electrode; and
A sound-absorbing device using a plasma actuator comprising a; dielectric formed between the first electrode and the second electrode. A sound wave proceeds in the central portion of the donut shape with an open center and a hollow formed therein, and an inlet portion for penetrating and introducing the sound wave toward the inner space of the donut shape, and the sound wave rotates and flows inside the donut shape a three-dimensional space part and a three-dimensional donut-shaped part including a discharge part for allowing sound waves that rotate and flow in the three-dimensional space part to be discharged toward an outer surface of the donut shape;
Plasma actuators installed at regular intervals in the inlet or outlet along the inner surface of the three-dimensional shape.
The plasma actuator is
a first electrode; a second electrode vertically spaced apart from the first electrode at a predetermined distance and disposed parallel to a surface of the first electrode; A sound-absorbing device using a plasma actuator comprising a; dielectric formed between the first electrode and the second electrode. 3. The method of claim 1 or 2,
The plasma actuator is
an alternating current (AC) electrically connected to the first electrode and the second electrode;
The AC unit divides the full-wave rectified voltage waveform obtained through the rectification bridge diode with a high-frequency capacitor and then is connected to a half-bridge converter that obtains an output voltage waveform identical to the input voltage through a half-bridge converter circuit to supply an AC voltage A noise-free sound absorbing device using a plasma actuator. 3. The method of claim 1 or 2,
The plasma actuator is a DBD (Dielectric Barrier Discharge) plasma actuator, in which a first electrode installed on the dielectric is an exposed electrode installed in a state exposed to the inner space, and the second electrode is an electrode installed under the dielectric is air and Noiseless sound absorbing device using a plasma actuator, characterized in that it is a submerged electrode installed by blocking the contact of the. 5. The method of claim 4,
The virtual contact portion where the exposed electrode and the submerged electrode meet virtually; is a noiseless sound absorbing device using a plasma actuator, characterized in that one of a rectangular arrangement, a sawtooth arrangement, or a wavy arrangement. 3. The method of claim 1 or 2,
Plasma actuator, characterized in that by adjusting the intensity and frequency of the voltage to the plasma actuator, to increase the collision rate between the medium particle (air particle) of the neutral sound wave and the plasma moving in a certain direction to a certain value or more to control the sound absorption A noise-free sound absorbing device using 3. The method of claim 1 or 2,
The electrical parameters of the plasma actuator are to change the voltage and frequency, or the shape of the waveform,
The variable of the dielectric changes the thickness or material, or the variable of the electrode changes the thickness, size, or material type of the electrode. 4. The method of claim 3,
The half-bridge converter is
a first resonant capacitor C1 and a second resonant capacitor C2 connected in series with each other;
Including a first switch (S1) and a second switch (S2) connected in series with each other;
One end of the primary side of the transformer is connected in parallel between the first resonant capacitor (C1) and the second resonant capacitor (C2), and the other end of the primary side of the transformer is connected to the first switch (S1) and the second switch ( S2) Noiseless sound absorbing device using a plasma actuator, characterized in that it is connected in parallel between.

Images