JP6595817B2 - Electrode for generating plasma, electrode panel and plasma reactor - Google Patents

Description

  The present invention relates to a plasma generating electrode, an electrode panel, and a plasma reactor, and more particularly to a plasma generating electrode and electrode suitable for an apparatus for removing PM (particulate matter) contained in exhaust gas from an internal combustion engine (engine). The present invention relates to a panel and a plasma reactor.

  Exhaust gas discharged from an engine, particularly a diesel engine, includes CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxide), PM (particulate matter), and the like.

  As a method for removing PM contained in exhaust gas, for example, PM is collected by a DPF (Diesel particulate filter), and the temperature of exhaust gas is raised by fuel post-injection or in-pipe injection, and the PM collected in the DPF is collected. Combustion techniques have been proposed. However, there is a problem of deterioration in fuel consumption due to consumption of fuel when burning PM. Further, in so-called city riding (city driving), the temperature of exhaust gas does not reach a high temperature for burning PM, so that this method is not suitable for small cars frequently used for city riding.

  Therefore, by incorporating electrodes in a plurality of plate-like dielectrics arranged so as to face each other in a direction parallel to and perpendicular to the flow direction of the exhaust gas, and applying a voltage between the electrodes, A method has been proposed in which low temperature plasma (non-equilibrium plasma) is generated to oxidize and remove PM in exhaust gas flowing between dielectrics.

Japanese Patent No. 4220778

  For example, as shown in FIG. 5, the electrode 101 has a lattice shape with a plurality of vertical line portions 102 extending in the vertical direction and a plurality of horizontal line portions 103 extending in the horizontal direction, and has a large number of rectangular meshes 104. is doing. When a voltage is applied between the electrodes 101, a discharge is generated, and plasma due to a dielectric barrier discharge is generated between the dielectrics.

  The discharge is generated starting from each edge (edge) of the vertical line portion 102 and the horizontal line portion 103 surrounding the mesh 104. The configuration shown in FIG. 5 has a problem that plasma cannot be generated efficiently because the number of edges that are the starting points of discharge is small.

  An object of the present invention is to provide an electrode for plasma generation, an electrode panel, and a plasma reactor capable of efficiently generating plasma.

  In order to achieve the above object, an electrode for plasma generation according to one aspect of the present invention is used in a plasma reactor including a dielectric extending in a flow direction of exhaust gas, and generates plasma by dielectric barrier discharge. A first linear portion extending in the first direction, a second linear portion extending in a direction intersecting the first direction, and a direction intersecting both the first direction and the second direction. A hole penetrating in the thickness direction is formed at a portion where the first linear portion, the second linear portion, and the third linear portion intersect with each other.

  According to this configuration, the first linear portion, the second linear portion, and the third linear portion that extend in the first direction, the second direction, and the third direction that intersect with each other are provided. Thereby, the edge per unit area (the 1st linear part, the 2nd linear part, and the 3rd is compared with the grid-like electrode which has the vertical line part and the horizontal line part which extend in the lengthwise direction and the widthwise direction, respectively. Since the number of each edge) of the linear portion is large and there are many starting points of discharge when a voltage is applied to the electrode, plasma can be generated efficiently.

  In addition, a hole penetrating in the thickness direction of the plasma generating electrode is formed at a portion where the first linear portion, the second linear portion, and the third linear portion intersect. Thereby, since the number of edges per unit area can be further increased, plasma can be generated more efficiently.

  As a result, the plasma intensity per electrode panel composed of dielectrics and electrodes increases, so even if the number of electrode panel stacks is reduced, PM contained in exhaust gas is oxidized and removed well. can do. By reducing the number of stacked electrode panels, the size and cost of the plasma reactor can be reduced.

  The first direction and the second direction may be directions orthogonal to each other, and the third direction may be a direction that intersects each of the first direction and the second direction at an angle of 45 °. In this case, it is preferable that the electrode for plasma generation further includes a fourth linear portion extending in a fourth direction orthogonal to the third direction.

  Thereby, the number of edges per unit area can be further increased, and plasma can be generated more efficiently.

  The present invention can be realized not only in the form of an electrode for plasma generation but also in the form of an electrode panel including a dielectric and an electrode or a plasma reactor including a plurality of electrode panels.

  That is, an electrode panel according to another aspect of the present invention is an electrode panel including a dielectric and an electrode for generating plasma by dielectric barrier discharge, and the plasma generating electrode is used as an electrode. Is.

  A plasma reactor according to still another aspect of the present invention is a plasma reactor in which a plurality of electrode panels are provided in parallel at intervals, and plasma is generated by dielectric barrier discharge between the electrode panels. As described above, the electrode panel is used.

  According to the present invention, the number of edges per unit area is large and a voltage is applied to the electrode as compared with a grid-like electrode having a vertical line portion and a horizontal line portion extending in the vertical direction and the horizontal direction, respectively. Since there are many starting points of discharge, plasma can be generated efficiently. As a result, the plasma intensity per electrode panel increases, so that PM contained in the exhaust gas can be satisfactorily oxidized and removed even if the number of stacked electrode panels is reduced. By reducing the number of stacked electrode panels, the size and cost of the plasma reactor can be reduced.

1 is a cross-sectional view schematically showing a configuration of a PM removal device using a plasma generating electrode, an electrode panel, and a plasma reactor according to an embodiment of the present invention. It is a top view which shows the composition of the electrode for plasma generation schematically. It is a top view which shows the other structure of the electrode for plasma generation schematically. FIG. 10 is a plan view schematically showing still another configuration of the plasma generating electrode. It is a top view which shows the structure of the conventional electrode for plasma generation schematically.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<PM removal device>

  FIG. 1 is a cross-sectional view schematically showing a configuration of a PM removal apparatus 1 using a plasma generating electrode 23, an electrode panel 21, and a plasma reactor 4 according to an embodiment of the present invention.

  The PM removal device 1 is a device for removing PM contained in exhaust gas discharged from an automobile engine (not shown), for example, and is interposed in the middle of an exhaust pipe 2 such as an exhaust pipe. The PM removal device 1 includes a flow tube 3, a plasma reactor 4, and a pulse generation power source 5.

  The flow pipe 3 has a tubular shape (cylindrical shape) having an exhaust gas inlet 11 and an exhaust gas outlet 12 at one end and the other end, respectively. The exhaust gas inlet 11 is connected to the engine side portion 2A of the exhaust pipe 2, and the exhaust gas outlet 12 is connected to the portion 2B of the exhaust pipe 2 opposite to the engine side. The exhaust gas discharged from the engine flows through the engine side portion 2A of the exhaust pipe 2, flows into the flow pipe 3 from the exhaust gas inlet 11, flows through the flow pipe 3, and the engine in the exhaust pipe 2 from the exhaust gas outlet 12 It flows out to the part 2B on the opposite side.

  The plasma reactor 4 is disposed in the flow pipe 3. The plasma reactor 4 includes a plurality of electrode panels 21.

The electrode panel 21 has a rectangular plate shape, and a structure in which a plasma generation electrode (hereinafter simply referred to as “electrode”) 23 is built in a dielectric 22, in other words, the electrode 23 is sandwiched between the dielectrics 22 from both sides. It has a configuration. In the electrode panel 21 having such a configuration, for example, a conductive paste is pattern-printed on one of a pair of square plate-like divided portions made of the material of the dielectric 22, and the conductive paste is sandwiched between the pair of divided portions. Thus, it produces by bonding one division part and the other division part, and baking them. As a material of the dielectric 22, for example, Al ₂ O ₃ (alumina) can be used. For example, a tungsten paste can be used as the conductive paste. Each of the plurality of electrode panels 21 extends in the flow direction of the exhaust gas in the flow pipe 3 (the direction from the exhaust gas inlet 11 to the exhaust gas outlet 12), and is arranged in parallel at equal intervals in a direction orthogonal to the flow direction. (Arranged to face each other).

  A positive wiring 24 and a negative wiring 25 are alternately connected to the electrode 23 in order from one end side in the stacking direction of the dielectric 22. The plus wiring 24 and the minus wiring 25 are electrically connected to the plus terminal and the minus terminal of the pulse generation power source 5, respectively.

<Electrode>

  FIG. 2 is a plan view schematically showing the configuration of the electrode 23.

  The electrode 23 includes a plurality of first linear portions 31, second linear portions 32, third linear portions 33, and fourth linear portions 34, thereby having a large number of right-angled triangular meshes 35. ing.

  Specifically, each of the plurality of first linear portions 31 extends linearly in a first direction parallel to the flow direction of the exhaust gas, and is provided at a constant interval in a second direction orthogonal to the first direction. Yes.

  The plurality of second linear portions 32 each extend linearly in the second direction, and are provided at regular intervals in the first direction. Thereby, the 1st linear part 31 and the 2nd linear part 32 have comprised the square lattice shape.

  The third linear portion 33 is a square lattice diagonal line formed by the first linear portion 31 and the second linear portion 32 in a third direction that intersects the first direction and the second direction at an angle of 45 °. It extends above.

  The fourth linear portion 34 extends in a square lattice-shaped diagonal line formed by the first linear portion 31 and the second linear portion 32 in a fourth direction orthogonal to the third direction.

  The electrode 23 has a hole 36 in the thickness direction at the center of each portion where the first linear portion 31, the second linear portion 32, the third linear portion 33, and the fourth linear portion 34 intersect. It is formed through. The hole 36 has, for example, a square shape having sides extending in the third direction and the fourth direction.

<Effect>

  When a pulse voltage (for example, peak voltage: 8 kV, pulse repetition frequency: 100 Hz) is applied between the electrodes 23 facing each other from the pulse generating power source 5, an edge (edge) surrounding each mesh 35 and each hole 36 is the starting point. As a result, dielectric barrier discharge occurs, and plasma is generated between the electrode panels 21 due to dielectric barrier discharge. Then, the PM contained in the exhaust gas flowing between the electrode panels 21 is oxidized (burned) and removed by the generation of plasma.

  The electrode 23 has a larger number of edges per unit area than the grid-like electrode (see FIG. 5) having a vertical line portion and a horizontal line portion extending in the vertical direction and the horizontal direction, respectively. Since there are many starting points of discharge when is applied, plasma can be generated efficiently. As a result, since the plasma intensity per electrode panel 21 increases, PM contained in the exhaust gas can be satisfactorily oxidized and removed even if the number of stacked electrode panels 21 is reduced as compared with the prior art. By reducing the number of stacked electrode panels 21, the size of the plasma reactor 4 can be reduced and the cost can be reduced. As a result, the size of the PM removal device 1 can be reduced and the cost can be reduced.

  In addition, the space | interval between the electrode panels 21 should just be a space | interval which a dielectric barrier discharge produces, for example, is set in the range of 0.2-5.0 mm.

<Modification>

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, although the hole 36 is formed in each portion where the first linear portion 31, the second linear portion 32, the third linear portion 33, and the fourth linear portion 34 intersect, the first linear portion The hole 36 may be formed in an arbitrary selected portion of the portion 31, the second linear portion 32, the third linear portion 33, and the fourth linear portion 34, instead of all of the intersecting portions. .

  Further, as the configuration of the electrode 23, the configuration shown in FIG. 3, that is, the configuration without the hole 36 may be adopted, or the third linear portion 33 or the first configuration from the configuration shown in FIG. A configuration in which the four linear portions 34 are omitted may be employed.

  As shown in FIG. 4, the electrode 23 is divided into a first portion 41, a second portion 42, and a third portion 43 in order from the upstream side in the flow direction of the exhaust gas, and the first portion 41 and the second portion 42. And the 3rd part 43 may be formed so that it may have the structure shown by FIG.2, FIG.3 and FIG.5, respectively.

  According to the configuration shown in FIG. 4, the first portion 41 has a larger number of edges per unit area than the second portion 42 and the third portion 43, and the voltage when the voltage is applied to the electrode 23. Since there are many starting points of discharge, plasma with high plasma density (plasma intensity) can be generated. Therefore, PM can be efficiently removed at the most upstream portion of the exhaust gas flow direction between the electrode panels 21, and PM can be suppressed from being deposited on the surface of the dielectric 22. Then, in the portion downstream of the most upstream portion in the exhaust gas flow direction between the electrode panels 21 (the portion facing the second portion 42 and the third portion 43), the PM that has flowed down without being removed at the most upstream portion. Even if the PM adheres to the surface of the dielectric 22, the PM can be removed by plasma generated in the downstream portion or active species (radical, ozone, etc.) flowing down from the upstream side. Accumulation can be suppressed.

  Therefore, PM can be prevented from being deposited on the entire surface of the dielectric 22. As a result, the PM removal performance of the PM removal device 1 (plasma reactor 4) can be maintained well.

  In the configuration shown in FIG. 4, the electrode 23 is equally divided into three parts, that is, a first part 41, a second part 42, and a third part 43. The ratio of the 2 part 42 and the 3rd part 43 may mutually differ.

  Moreover, the electrode 23 may be comprised by the 1st part 41 which has the structure shown by FIG. 2, and the 2nd part 42 which has the structure shown by FIG. 3, and has the structure shown by FIG. You may be comprised by the 1st part 41 and the 3rd part 43 which has the structure shown by FIG.

  The shape of the hole 36 is not limited to a square shape, and may be a rectangular shape, a circular shape, a triangular shape, a pentagonal polygon or other shapes.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

4 Plasma reactor 21 Electrode panel 22 Dielectric 23 Electrode (Plasma generating electrode)
31 1st linear part 32 2nd linear part 33 3rd linear part 36 hole

Claims (3)

An electrode for plasma generation used for a plasma reactor having a dielectric extending in the flow direction of exhaust gas, and for generating plasma by dielectric barrier discharge,
A first linear portion extending in a first direction in a plane ;
A second linear portion extending in a direction intersecting the first direction in the plane ;
A third linear portion extending in a direction intersecting with both the first direction and the second direction in the plane ,
A plasma generating electrode, wherein a hole penetrating in a thickness direction perpendicular to the plane is formed at a portion where the first linear portion, the second linear portion, and the third linear portion intersect. A dielectric,
An electrode for generating plasma by dielectric barrier discharge,
An electrode panel, wherein the plasma generating electrode according to claim 1 is used as the electrode. A plasma reactor in which a plurality of electrode panels are provided in parallel at intervals, and plasma is generated by dielectric barrier discharge between the electrode panels,
A plasma reactor in which the electrode panel according to claim 2 is used as the electrode panel.

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