JP2008259927A - Discharge reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge reactor, wherein the power output up of plasma discharge and the improvement in cleaning performance are attained without enlarging the size of the discharge reactor. <P>SOLUTION: The discharge reactor is provided with: a central electrode 2 to be connected to a high-voltage electrode 1; internal electrodes 3A-3E which are connected to the central electrode 2 and on the outer peripheral part 11 of each of which a groove part 12 is formed; a dielectric 4 arranged on the peripheries of the internal electrodes 3A-3E to surround them; and an external electrode 5 arranged on the outer periphery of the dielectric 4. The outer peripheral part 11 of one 3E of the internal electrodes 3A-3E is brought into contact with the inside surface 4a of the dielectric 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to, for example, a discharge reactor, and more particularly, to a technique for increasing the output of corona discharge (plasma discharge) and improving purification performance.

  For example, as shown in FIG. 6, the barrier discharge reactor includes an internal electrode 101 made of stainless steel bolts, a quartz tube 102 provided around the internal electrode 101, and an outer periphery of the quartz tube 102. (See Non-Patent Document 1, for example). FIG. 6 illustrates three types of barrier discharge reactors.

  Such a barrier discharge reactor generates a corona discharge (plasma) inside the reactor by applying high-frequency alternating current or a pulse voltage between the internal electrode 101 and the external electrode 103, and is discharged from an automobile or the like by the corona discharge. The exhaust gas is activated and purified.

  In addition, as shown in FIG. 7, a disk-shaped internal electrode 106 is attached to the center electrode 105 connected to the high voltage electrode 104, and a dielectric 107 and an external electrode 108 are provided around the internal electrode 106, respectively. Discharge reactors with an arranged structure are known.

  The internal electrode 106 of this discharge reactor is formed as a cylindrical body having a honeycomb structure by winding a plurality of corrugated sheets 109 and a flat plate 110 made of stainless steel around the central electrode 105 so that the corrugated sheet 109 is formed on the outside and the flat plate 110 is formed on the inside. Is formed.

The barrier discharge type plasma reactor shown in FIG. 7 is connected to the middle part of the automobile exhaust pipe 111 and functions to purify exhaust gas discharged from the automobile or the like with plasma emitted from the internal electrode 106.
“New edition Electrostatic Handbook” 31

  In the barrier discharge type plasma reactor shown in FIG. 7, plasma is generally easily generated from both end portions 106 </ b> A and 106 </ b> B in the thickness direction of the internal electrode 106.

  In order to improve the purification performance, it is necessary to generate plasma as much as possible. For this purpose, it is necessary to increase the end portions 106A and 106B of the internal electrode 106 where plasma is likely to be generated. Increasing the number of internal electrodes 3 naturally increases the number of ends where plasma is likely to be generated, but has the disadvantage of increasing the size of the discharge reactor itself.

  Accordingly, in order to solve the above-described problems, the present invention provides a discharge reactor that can increase the output of plasma discharge (corona discharge) and improve purification performance without increasing the size of the discharge reactor. Objective.

  The discharge reactor according to claim 1 includes a central electrode connected to a high voltage electrode, an internal electrode connected to the central electrode and having a groove formed in an outer peripheral portion, and surrounding the internal electrode. A dielectric provided in the periphery; and an external electrode provided in the outer periphery of the dielectric.

  A second aspect of the present invention is the discharge reactor according to the first aspect, wherein a plurality of the internal electrodes are arranged at a predetermined interval with respect to the center electrode, and an outer periphery of one of the internal electrodes is arranged. The portion is in contact with the dielectric.

  The invention described in claim 3 is the discharge reactor according to claim 1 or 2, characterized in that the high voltage electrode side is the downstream side of the gas flow.

  According to the discharge reactor of the first aspect, since the groove portion is formed on the outer peripheral portion of the internal electrode, end portions (edges) are formed on both sides of the groove portion. Plasma is also generated from the end. Therefore, the plasma output is greatly increased, and the purification performance can be further enhanced when the discharge reactor is used as an exhaust gas purification device.

  According to the discharge reactor of the second aspect, since one of the plurality of internal electrodes is brought into contact with the outer periphery of the dielectric, creeping discharge (the discharge electrode and the dielectric are in contact with each other) Discharge) occurs, and the purification performance is further improved. Further, according to this discharge reactor, the internal electrode attached to the center electrode is stabilized by the internal electrode supported by the dielectric.

  According to the discharge reactor of the third aspect, if the high voltage electrode side is the downstream side of the gas flow, contamination due to soot and SOC (soluble) generated in the high voltage electrode can be reduced. In addition, SOC is an abbreviation for soluble organic compounds.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a partially enlarged perspective view showing the discharge reactor of the present embodiment in a partially broken view, FIG. 2 is a perspective view of an internal electrode group attached to a central electrode in the discharge reactor of FIG. 1, and FIG. It is an expansion perspective view of an internal electrode among 1 discharge reactors.

  As shown in FIG. 1, the discharge reactor of the present embodiment includes a center electrode 2 connected to the high voltage electrode 1 and an internal electrode 3 (3A to 3E) having a honeycomb structure connected to the center electrode 2. And a dielectric 4 provided around the inner electrode 3 and an outer electrode 5 provided around the outer periphery of the dielectric 4 and discharged from an internal combustion engine such as an automobile. It is connected to the middle part of the automobile exhaust pipe 6 for purifying and discharging exhaust gas.

  The center electrode 2 is formed as an elongated cylindrical body, and is arranged with its longitudinal direction directed in the flow direction of exhaust gas (the direction indicated by the arrow X in FIG. 1). A high voltage electrode 1 is connected to the center electrode 2. An insulator 7 formed by winding an insulating material is provided at the insertion portion of the high voltage electrode 1 inserted into the reactor. By providing this insulator 7, discharge to the high voltage electrode 1 is prevented.

  As shown in FIG. 2, a plurality of internal electrodes 3 are provided at predetermined intervals along the longitudinal direction of the center electrode 2. In the present embodiment, the internal electrode 3 is composed of a total of five electrode groups: four internal electrodes 3A to 3D having the same size and one large-diameter internal electrode 3E having a larger diameter. .

  As shown in FIG. 3, the internal electrode 3 (3 </ b> A to 3 </ b> E) includes a plurality of corrugated plates 8 and flat plates 9 made of stainless steel, and a plurality of the central electrodes 2 so that the corrugated plate 8 is on the outside and the flat plate 9 is on the inside. It is formed as a cylindrical body that is wound to form a honeycomb structure. Since the internal electrode 3 configured as described above includes the corrugated plate 8 and the flat plate 9, the internal electrode 3 includes a plurality of holes 10 that serve to reduce pressure loss therebetween. The purification performance may be further improved by attaching a purification catalyst to the surface of the internal electrode 3.

  In the present embodiment, for example, four internal electrodes 3A to 3D having the same size have a thickness T of 10 mm and a diameter D of 32 mm, and the large-diameter internal electrode 3E has a thickness T of 10 mm and a diameter D of 10 mm. Larger than 46 mm. These sizes are merely examples, and are not limited to the dimensions described above.

  In particular, in the present embodiment, a groove portion 12 is formed in the outermost peripheral portion 11 of the corrugated plate 8 in these four internal electrodes 3A to 3D in order to further increase the generation of plasma. For example, a slit 12 having a groove width W of about 2 mm is formed on the outer peripheral portion 11 of the internal electrodes 3 </ b> A to 3 </ b> D to form the groove 12. The depth of the groove 12 is preferably, for example, about 1/2 of the corrugated plate height of the outermost corrugated plate 8. If the depth of the groove 12 is too deep, the corrugated plate 8 and the flat plate 9 are split. Therefore, after the corrugated plate 8 and the flat plate 9 are overlapped and wound, a plurality of outer peripheral portions are welded by spot welding or the like, and the outer top portion of the outermost peripheral corrugated plate 8 is cut off slightly deeper than the plate thickness by a cutter.

  By forming the groove 12, the both ends of the groove 12 are formed with the end portions 3c and 3d which are portions for generating plasma, as with the end portions 3a and 3b of the internal electrode 3 in the thickness direction. The That is, one internal electrode 3 has a total of four plasma generation sites which are the end portions 3a to 3d that are likely to generate plasma. In the present embodiment, since there are four internal electrodes 3 in which the groove portion 12 is formed, the plasma generating portion has a total of 16 end portions 3a to 3d.

  In addition, although the groove part 12 is not formed in the large diameter internal electrode 3E, you may form the groove part 12 as needed.

  The dielectric 4 is formed as a cylindrical tube from ceramics, alumina, glass, quartz, or the like, for example. The dielectric 4 is formed as a cylindrical tube that accommodates all the internal electrodes 3A to 3E therein, and is arranged with its axial direction directed toward the exhaust flow direction. In the present embodiment, the outer peripheral portion of the internal electrode 3E having a large diameter out of the five internal electrodes 3A to 3E described above is brought into contact with the inner surface 4a of the dielectric 4.

  For example, a quartz tube having a thickness of 1.2 mm and an inner diameter of 46 mm, which is the same as the outer diameter of the large-diameter internal electrode 3E, was used as the dielectric 4.

  The external electrode 5 is provided on the peripheral surface so as to surround the outer periphery of the dielectric 4. The position where the external electrode 5 is provided is at least a position facing the internal electrode 3 (3A to 3E). In the present embodiment, an electrode tube made of Kovar metal is used for the external electrode 5 and its thickness is 1 mm.

  In the discharge reactor configured as described above, when a high-frequency alternating current or a pulse voltage is applied to the internal electrodes 3 (3A to 3E) via the high-voltage electrode 1 and the center electrode 2, plasma ( Corona discharge) occurs, and the NO and residual hydrocarbon contained in the exhaust gas can be activated and purified by the corona discharge. In particular, since plasma is easily generated from the end portions 3 a to 3 d of the internal electrode 3, the number of plasma generation sites can be increased by forming the groove portion 12 in the outer peripheral portion 11 of the internal electrode 3 and increasing the number of the end portions 3 a to 3 d. Increases plasma output. Thus, according to the discharge reactor of the present embodiment, the plasma output can be increased without increasing the number of internal electrodes 3, and the exhaust gas purification performance can be greatly improved without increasing the size of the apparatus itself. It becomes possible.

  Further, according to the discharge reactor of the present embodiment, since the outer peripheral portion 11 of one internal electrode 3E of the plurality of internal electrodes 3 is brought into contact with the inner surface 4a of the dielectric 4, creeping discharge is generated at the contact portion. And the purification performance can be further improved. Further, a plurality of inner electrode groups that are heavy by being attached to the center electrode 2 are supported by one inner electrode 3E on the inner surface 4a of the dielectric 4, so that the distance between the electrode group and the dielectric 4 is stable. Will be held.

  Further, according to the discharge reactor of the present embodiment, if the flow direction X of the exhaust gas is opposite to the direction shown in FIG. 1 and the high voltage electrode 1 side is the downstream side of the gas flow, the high voltage electrode 1 becomes Contamination caused by soot and SOC can be reduced.

  Here, a purification performance experiment using the discharge reactor of the present embodiment was actually performed. Specifically, exhaust gas was purified by performing DC pulse discharge of 14 kV and 4 kHz. FIG. 4 is a characteristic diagram showing the purification performance, and FIG. 5 shows the result of the characteristic diagram showing the plasma output characteristic.

  In FIG. 4, the mark ● indicates the purification performance when the groove 12 is formed, and the mark ▼ indicates the purification performance when the groove 12 is not formed. The mark ● in FIG. 5 indicates the plasma output characteristics when the groove 12 is formed, and the mark ▼ indicates the plasma output characteristics when the groove 12 is not formed.

  As can be seen from these results, the NO purification performance was improved by 40% and the input power was improved by 25% when the groove 12 was formed in the internal electrode 3 compared to when the groove 12 was not formed. Therefore, if the discharge reactor of the present embodiment is used, the purification ratio per input power can be greatly improved.

  The specific embodiment to which the present invention is applied has been described above. However, the above-described embodiment is an example, and the present invention is not limited to this embodiment.

FIG. 1 is an enlarged perspective view of a main part of the discharge reactor according to the present embodiment, partially broken away. FIG. 2 is a perspective view of the internal electrode group attached to the center electrode in the discharge reactor of FIG. FIG. 3 is an enlarged perspective view of an internal electrode in the discharge reactor of FIG. It is a characteristic view which shows purification performance. FIG. 5 is a characteristic diagram showing plasma output characteristics. It is a schematic block diagram of the conventional discharge reactor. It is a schematic block diagram of the discharge reactor of other conventional structures.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... High voltage electrode 2 ... Center electrode 3 (3A-3E) ... Internal electrode 3a-3d ... End part used as a plasma generation site 4 ... Dielectric 5 ... External electrode 6 ... Automotive exhaust pipe 7 ... Insulator 11 ... Inside Electrode outer peripheral part 12 ... groove part

Claims (3)

A central electrode (2) connected to the high voltage electrode (1);
An internal electrode (3A-3E) connected to the central electrode (2) and having a groove (12) formed in the outer peripheral part (11);
A dielectric (4) provided around the internal electrodes (3A to 3E);
An external electrode (5) provided on the outer periphery of the dielectric (4). The discharge reactor according to claim 1,
A plurality of the internal electrodes (3A to 3E) are arranged at a predetermined interval with respect to the center electrode (2), and an outer peripheral portion (11) of one internal electrode (3E) among the internal electrodes (3A to 3E) is arranged. A discharge reactor characterized by contacting with the dielectric (4). The discharge reactor according to claim 1 or 2,
A discharge reactor characterized in that the high voltage electrode (1) side is the downstream side of the gas flow.

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