JP4445374B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device that removes particulates from exhaust gas of an internal combustion engine such as a diesel engine.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done conventionally.

  This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow paths partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, and are spontaneously combusted and removed when the exhaust gas moves to an operating region. For example, in a vehicle that travels only on a congested road such as a route bus in Tokyo, the accumulated amount is higher than the processing amount of particulates because the operation above the required predetermined temperature does not continue for a long time. There is a possibility that the particulate filter may be clogged.

  For this reason, plasma-assisted exhaust purification devices are being developed so that particulates can be burned and removed well even in the operating region where the exhaust temperature is low, and this type of exhaust purification device discharges into the exhaust gas to generate plasma. The exhaust gas is excited and active radicals such as O radicals and OH radicals are generated, and these exhaust gas excitation components are in an activated state, so even in an operation region where the exhaust temperature is low. It is possible to burn and remove the particulates (oxidation treatment) satisfactorily.

For example, in Patent Document 1 and Patent Document 2 below, ceramic pellets forming a dielectric material are filled between an outer electrode and an inner electrode made of cylindrical stainless steel that has been perforated, and a packed layer of the pellet is formed. A plasma-assisted exhaust purification system is proposed in which exhaust gas is allowed to flow and particulates in the exhaust gas are collected, while plasma is generated by discharging between the outer electrode and the inner electrode. Has been.
Japanese translation of PCT publication No. 2002-501813 Japanese translation of PCT publication No. 2002-511332

  However, in such a plasma assisted type exhaust gas purification device that has been proposed in the past, it is necessary to support both ends of the electrodes arranged opposite to each other to be discharged between each other by an insulating structure. If a flat surface that connects the two electrodes linearly is formed by an object, creeping discharge along the surface tends to occur and the plasma concentrates, so that uniform plasma can be generated between the two electrodes. There is a risk that it will become impossible to perform, or wasteful discharge will occur outside the region to be discharged, resulting in consumption of excess electrical energy.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma-assisted exhaust purification device that can generate uniform plasma only in a region to be discharged.

  The present invention relates to an electrode plate having a ventilation structure, a plurality of electrode rods arranged with a plasma generation space at a uniform interval with respect to the surface of the electrode plate, and having a surface insulated by a dielectric, and an electrode plate And a filter means configured in at least one of the plasma generation spaces, the exhaust gas is allowed to flow through the plasma generation space and the electrode plates through the gaps between the electrode rod rows, and each electrode plate and each electrode rod A plasma assist type exhaust gas purification device that can apply a voltage required for discharge between the electrode rod and the both ends of each electrode rod by an insulating structure. A power feeding portion is formed outside the insulating structure by penetrating one insulating structure, and an insulating coating made of the dielectric is extended to the other end of each electrode rod longer than the end. And the extension end A protruding portion is formed on the surface on the side opposite to the power feeding portion of the one insulating structure, and a protruding portion that protrudes toward the other insulating structure is formed on the other insulating structure. It is characterized in that it is supported in a state where the end portions are butted.

  Thus, when the exhaust gas is caused to flow through the plasma generation space and the electrode plate through the gap between the row of electrode rods, the exhaust gas is configured in at least one of the electrode plate and the plasma generation space. Particulates are collected when passing through the electrode, so that if necessary voltage is applied between the electrode plate and each electrode rod when necessary, the surface between each electrode rod and electrode plate whose surface is insulated is coated. As a result of barrier discharge, which generates low-temperature plasma (non-thermal equilibrium plasma) in the plasma generation space, the exhaust gas is excited and active radicals such as O radicals and OH radicals are generated. As a result, the particulates are effectively removed by combustion (oxidation treatment).

  At this time, since the end portion of the electrode plate is supported in a state where the end portion of the electrode plate abuts against the raised portion of the one insulating structure, the space between the end portion of the electrode plate and each electrode rod is the one of the insulating structure. The plane is not connected in a straight line, and creeping discharge along the plane of one insulating structure does not occur.

  Further, on the other insulating structure side, only the extended end portion of the insulating coating of each electrode rod is penetrated and fixed to the insulating structure, and each electrode rod itself does not reach the insulating structure. The other end of each electrode rod is spaced from the other insulating structure, and the other end of each electrode rod and the electrode plate are linearly connected by the plane of the other insulating structure. The creeping discharge along the plane of the other insulating structure does not occur.

  If creeping discharge is prevented between each electrode rod and electrode plate in this way, it is avoided that low-temperature plasma concentrates in the vicinity of both insulating structures in the plasma generation space, and the plasma generation space is uniform. It is possible to generate various low-temperature plasmas.

  In addition, if the end of the electrode plate is supported against the raised portion of one of the insulating structures, the end of the electrode plate is also spaced apart from the feeding portion of each electrode rod. Since the end of the electrode plate and the power feeding portion are not linearly connected by the plane of the one insulating structure, creeping discharge along the plane of the one insulating structure outside the plasma generation space does not occur. .

  Furthermore, in the present invention, it is preferable to form a stepped portion that protrudes so as to surround the power supply portion around the power supply portion of one insulating structure. Since the stepped portion is interposed between the structure and the discharge, it is difficult for the discharge to occur, and a discharge occurs between the power supply unit and the electrode plate by going around the outside of the insulating structure. There is very little risk of electrical discharge occurring between the structure.

  According to the exhaust emission control device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, it is possible to prevent creeping discharge along the planes of both insulating structures between each electrode rod and the electrode plate, so that in the region to be discharged. Uniform low-temperature plasma can be generated in a certain plasma generation space, and wasteful discharge in regions other than the region where discharge is desired is difficult to occur, and excess electric energy consumption can be suppressed.

  (II) According to the invention described in claim 2 of the present invention, since the step portion of the insulating structure is interposed between the power feeding portion of each electrode rod and the surrounding various structures, the power feeding portion And the surrounding various structures can be made difficult to occur, and the outside of the insulation structure can cause a discharge between the power supply unit and the electrode plate. It is possible to avoid as much as possible the possibility of electric discharge between the structure and further save electric energy consumption.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 7 show an example of an embodiment of the present invention. Reference numeral 1 in FIG. 1 denotes a diesel engine (internal combustion engine) equipped with a turbocharger 2, and intake air introduced from an air cleaner 3. 4 is introduced into the compressor 2a of the turbocharger 2 through the intake pipe 5 and pressurized, and the pressurized intake air 4 is distributed and introduced to each cylinder of the diesel engine 1 via the intercooler 6.

  Further, exhaust gas 8 discharged from each cylinder of the diesel engine 1 through the exhaust manifold 7 is sent to the turbine 2b of the turbocharger 2, and the exhaust gas 8 driving the turbine 2b is supplied to the plasma assist in the middle of the exhaust pipe 9. Particulates are collected through the exhaust gas purification device 10 and then discharged.

  This exhaust purification device 10 has a structure as will be described in detail with reference to FIGS. 2 to 7 below, and the required number is collected by a casing 12 (only part of which is shown in FIG. 2). Among the drawings to be referred to in the following description, FIG. 2 is a plan view showing a schematic structure of the exhaust purification device 10, and FIG. 3 is a view of the exhaust purification device 10 from the front side. 4 is a perspective view showing a state in which the front insulating structure 13 of FIG. 3 is removed, FIG. 5 is a perspective view of the exhaust purification device 10 viewed from the rear side, and FIG. 6 is a rear side view of FIG. FIG. 7 is a perspective view of a state in which the exhaust purification apparatuses 10 are arranged in parallel, as viewed from the rear side.

  As shown in FIGS. 2 to 6, the exhaust emission control device 10 includes a pair of flat plate electrodes 15 forming a ventilation structure facing each other with a required gap therebetween, and each flat plate electrode 15 between the flat plate electrodes 15. A plurality of electrode rods 18 arranged in parallel with a gap of several millimeters across the plasma generation space 16 and having a surface insulated by a dielectric 17, and each plate electrode 15 and each electrode rod. Both ends of 18 are supported by insulating structures 13 and 14.

  Here, in this embodiment, the case where the plate electrode 15 itself is configured as a filter means is illustrated, and more specifically, the plate electrode 15 is formed by a metal filter capable of collecting particulates. A ventilation structure is formed.

  This type of metal filter includes micron-order metal fibers laminated and sintered, metal powder sintered bodies, metal mesh laminated and sintered, metal mesh sintered metal powder, etc. Should be adopted.

  However, a cordierite honeycomb filter, a ceramic fiber filter, a ceramic foam, an alumina pellet or the like can be interposed as a filter means in the plasma generation space 16, and in this case, the plate electrode 15 is not necessarily provided. It does not need to be configured as a filter means, and may be configured as a flat plate electrode 15 having a simple ventilation structure made of a metal mesh, punching metal, or the like. Of course, for the purpose of obtaining a high collection rate, the plate electrode 15 itself may be configured as a filter means, and a filter means may be used in the plasma generation space 16 together.

  Incidentally, when the plasma generating space 16 is filled with dielectric particles such as ceramic pellets to form a filter means, electric charges concentrate at the respective contact points of the particles to form a strong local electric field, thereby reducing the temperature. Plasma is likely to be generated (the same effect can be obtained when ceramic fiber or ceramic foam is filled), and the filter means interposed in the plasma generation space 16 extends in the opposing direction of the plate electrode 15 and the electrode rod 18. If a large number of planes are formed, creeping discharge along the planes is promoted and low-temperature plasma is easily generated.

  On the other hand, a gas inlet 20 for introducing the exhaust gas 8 into the introduction space 19 sandwiched between the two rows of the electrode rods 18 is opened in the front insulating structure 13, and the rear side The insulating structure 14 has a closed structure that blocks the flow of the exhaust gas 8, and the exhaust gas 8 introduced into the introduction space 19 from the upstream side through the gas inlet 20 passes through the gaps between the row groups of the electrode rods 18. It passes through the plasma generation space 16 and the plate electrode 15 and flows downstream.

  It should be noted that dielectric dummy tubes 21 are arranged in the left-right direction above and below the two row groups of the electrode rods 18, and the flow of the exhaust gas 8 that bypasses each row group of the electrode rods 18 up and down. In addition, the part opened to the upper part and the lower part of the introduction space 19 is closed by the casing 12 whose part is shown in FIG.

  Further, the rear end of each electrode rod 18 penetrates the rear insulating structure 14 to form a power feeding portion 22 made of a conductor plate outside the insulating structure 14. On the other hand, a power source 23 outside the casing 11 is connected through the housing 12 and each plate electrode 15 is grounded, and an AC high voltage necessary for discharge between each plate electrode 15 and each electrode rod 18 ( DC pulse high voltage is also possible).

  Here, in this embodiment, when the electrode rod 18 whose surface is insulated is formed, the electrode rod 18 is inserted into the dielectric 17 formed so as to form a tubular shape, and the electrode rod 18 is covered with the insulation coating. However, the front end of each electrode rod 18 is inserted only halfway through the tube of the dielectric 17, and the front end of each electrode rod 18 is longer than the end. An insulating coating with a dielectric 17 is formed to extend, and this extended end portion 17 a is fixed to the insulating structure 13 on the front side.

  However, when the electrode rod 18 whose surface is insulated is formed, the electrode rod 18 is formed by coating the inner peripheral surface of the dielectric 17 formed in a tubular shape with a paste of an electrode material such as silver. Therefore, in such a case, the coating is kept halfway in the tube of the dielectric 17, and the extended end portion 17 a is formed at the front end portion of each electrode rod 18. You can do that.

  Further, at the left and right width ends of the front surface on the side opposite to the power feeding portion 22 of the insulating structure 14 on the rear side, a protruding portion 24 that protrudes to the front side is formed in the vertical direction. The rear end portion of the flat plate electrode 15 is connected and supported in a face-to-face state, and the power supply portion 22 is surrounded around the power supply portion 22 of the rear insulating structure 14. A raised stepped portion 25 is formed.

  Then, as shown in FIG. 7, the exhaust gas purification devices 10 as described above are arranged in parallel with the introduction direction of the exhaust gas 8 being aligned, and the exhaust gas 8 that has passed through the plate electrode 15 between adjacent ones is disposed downstream. A plasma assist type exhaust purification apparatus 10 is configured by securing the exhaust space 26 to be guided.

  Here, when securing the exhaust space 26 between the exhaust purification devices 10, a ridge projecting outward in the width direction is formed on three sides excluding the one side on the rear side of each flat plate electrode 15. Protrusions (upper, middle, and lower three-stage arrangement in the drawing) may be formed on both sides of the insulating structure 14 (see FIGS. 3 to 7).

  Thus, if the exhaust gas purification device 10 is configured in this way, the exhaust gas 8 from the upstream side is introduced into the introduction space 19 of each exhaust gas purification device 10, and the plasma generation space is formed from the gap between each row group of the electrode rods 18. 16 and the plate electrode 15 and flows downstream, and particulates are collected when the exhaust gas 8 passes through the plate electrode 15 forming the metal filter. When an AC high voltage is applied between the electrode rods 18 and the electrode rods 18, a barrier discharge occurs between the electrode rods 18 whose surfaces are insulated and coated with the dielectric 17 and the flat plate electrodes 15. As a result, low temperature plasma (non-thermal equilibrium plasma) is generated, and the exhaust gas 8 is excited to generate active radicals such as O radicals and OH radicals. Only in so that the particulates are efficiently burned and removed (oxidized).

  At this time, since the end of the plate electrode 15 is supported with the raised portion 24 of the insulating structure 14 on the rear side, the end of the plate electrode 15 and each electrode rod 18 are insulated from each other. The plane of the structure 14 is not connected in a straight line, and creeping discharge along the plane of the insulating structure 14 does not occur.

  Further, in the insulating structure 13 on the front side, only the extended end portion 17a of the insulating coating of each electrode rod 18 is fixed to the insulating structure 13 so that each electrode rod 18 itself reaches the insulating structure 13. Since it does not reach, the front end of each electrode rod 18 is spaced apart from the insulating structure 13, and the space between the front end of each electrode rod 18 and the plate electrode 15 is due to the plane of the insulating structure 13. It becomes impossible to connect linearly, and creeping discharge along the plane of the insulating structure 13 does not occur.

  When creeping discharge along the planes of the two insulating structures 13 and 14 is prevented between the electrode rods 18 and the plate electrodes 15 in this way, the vicinity of the two insulating structures 13 and 14 in the plasma generation space 16 is prevented. Thus, the concentration of the low temperature plasma is avoided, and the uniform low temperature plasma can be generated in the plasma generation space 16.

  In addition, if the end of the flat plate electrode 15 is supported against the raised portion 24 of the insulating structure 14 on the rear side, the end of the flat plate electrode 15 is connected to the feeding portion 22 of each electrode rod 18. In contrast, the end portion of the plate electrode 15 and the power feeding portion 22 are not spaced from each other and are not linearly connected by the plane of the insulating structure 14, so that the plane of the insulating structure 14 outside the plasma generation space 16 is not connected. There is no creeping discharge along.

  Therefore, according to the above embodiment, it is possible to prevent creeping discharge along the planes of both insulating structures 13 and 14 between each electrode rod 18 and the plate electrode 15, so that plasma generation that is a region to be discharged is generated. Uniform low-temperature plasma can be generated in the space 16, and wasteful discharge in areas other than the region where discharge is desired is difficult to occur, and excess electric energy consumption can be suppressed.

  Further, particularly in this embodiment, the stepped portion 25 of the insulating structure 14 is interposed between the power feeding portion 22 of each electrode rod 18 and the surrounding various structures. It is also possible to make it difficult for electric discharge to occur between various structures, and electric discharge occurs around the outside of the insulating structure 14 between the power supply unit 22 and the plate electrode 15, or other than the power supply unit 22 and this device. Therefore, it is possible to avoid as much as possible the possibility of electric discharge with the structure, and to further save electric energy consumption.

  Note that the exhaust emission control device of the present invention is not limited to the above-described embodiment. In the description of the embodiment described above, the case where the electrode plate of the ventilation structure is a flat plate electrode is illustrated. However, a cylindrical cylindrical electrode may be employed as the electrode plate of the ventilation structure, and in this case, a plasma generation space having a uniform interval is sandwiched between the inner peripheral surface of the cylindrical electrode. It is only necessary to arrange a plurality of electrode rods in an annular shape, and it is also possible to attach a curved surface shape other than a cylindrical shape to the electrode plate of the ventilation structure, and does not depart from the gist of the present invention. Of course, various changes can be made within the range.

It is the schematic which shows an example of the form which implements this invention. It is a top view which shows schematic structure of an exhaust gas purification apparatus. It is the perspective view which looked at the exhaust gas purification device from the front side. It is a perspective view which shows the state which removed the insulation structure of the front side of FIG. It is the perspective view which looked at the exhaust gas purification device from the rear side. It is a perspective view which shows the state which removed the insulating structure of the rear side of FIG. It is the perspective view which looked at the state which arranged each exhaust gas purification device in parallel from the back side.

Explanation of symbols

8 Exhaust gas 10 Exhaust purification device 13 Insulating structure 14 Insulating structure 15 Flat plate electrode (electrode plate: filter means)
16 Plasma generation space 17 Dielectric 17a Extended end 18 Electrode rod 22 Feeding portion 24 Raised portion 25 Stepped portion

Claims (2)

  An electrode plate having a ventilation structure, a plurality of electrode rods arranged with a plasma generation space at a uniform interval with respect to the surface of the electrode plate, and having a surface insulated by a dielectric, and the electrode plate and the plasma generation space And at least one of the filter means, the exhaust gas is allowed to flow through the plasma generation space and the electrode plate through the gap between the electrode rod rows, and between each electrode plate and each electrode rod. A plasma-assist type exhaust gas purifying apparatus capable of applying a voltage necessary for discharge, wherein each end of each electrode rod is supported by one end when each end of each electrode rod is supported by an insulating structure. A feed portion is formed outside the insulating structure through the insulating structure, and an insulating coating made of the dielectric is extended to the other end of each electrode rod longer than the end, and the extended end Insulation of the other part A ridge is formed on the surface of the one insulating structure on the side opposite to the feeding portion, and a protruding portion is projected to the other insulating structure, and the end of the electrode plate is abutted against the protruding portion. An exhaust purification device characterized by being supported in a heated state.   The exhaust emission control device according to claim 1, wherein a stepped portion is formed around the power supply portion of one insulating structure so as to surround the power supply portion.

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