JPS63272911A - Engine exhaust gas purifying device - Google Patents

Abstract

PURPOSE:To aim at enhancing the dissociation and removal action of NOx by disposing several negative and positive electric discharge electrodes arranged alternately in the direction of exhaust gas communication, in an exhaust gas passage, and by constituting each electrode in such a way that conductive wires orthogonal to the direction of exhaust gas communication are carried by an insulator. CONSTITUTION:A plurality of electric discharge electrodes 3 are disposed, being spaced at suitable intervals in the direction of exhaust communication, in an electric discharge chamber 2a which is formed in an exhaust passage 2 from an engine 1. The electrodes 3 are connected to a high voltage generating device 4 so that the positive and negative electrodes 3 are alternately arranged. In each electrode 3, a plurality of mesh-like conductive wires 6 are carried on one side surface of a disc-like ceramic foam member 5 which is a porous member having several through holes 7 which are directed at random. In this arrangement, high voltage is applied to the electrodes 3 so as to generate electric discharge fields through which exhaust gas is led. In this phase, NOx is dissociated from oxygen and nitrogen in the exhaust gas 6 which is therefore purified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine exhaust purification device that utilizes a silent discharge field.

(Prior art) Gasoline engine or diesel engine (hereinafter referred to as
The exhaust gas of an engine (simply referred to as an engine) contains Co (-carbon oxide), C07 (carbon dioxide), HC (hydrocarbon), and N.
It contains 0x (nitrogen oxide) and the like, and among these, nitrogen oxide NOx is the main cause of photochemical smog and is considered to be the most harmful.

Therefore, various methods have been tried in the past in order to remove this nitrogen oxide NOX. For example, a method has been adopted in which harmful gases are reduced and rendered harmless using a catalytic converter, but with this reduction method, 0. The problem remains that when there is a sufficient amount of nitrogen oxide NOx, it may not be possible to remove the nitrogen oxide NOx.

On the other hand, in recent years, research has been progressing on methods that use electrical energy to remove nitrogen oxides (NOx). discharge), nitrogen oxide NOX is reduced to 0.
．． And N! There are reports that it can be broken down into As a prior art that focuses on this point, it has already been proposed that a dissociation tube is connected to the exhaust pipe of an engine, which acts to dissociate and remove nitrogen oxides by corona discharge. It is configured to generate a corona discharge between a corona discharge needle protruding from the cylinder peripheral wall toward the axial center and a center ball installed at the axial center (see Japanese Patent Laid-Open No. 61-31615). ).

(Problems to be Solved by the Invention) In the case of the above-mentioned known example, nitrogen oxide NOx is dissociated by a corona discharge field in the dissociation cylinder connected to the exhaust pipe, but the exhaust flow in the discharge field Because no countermeasures have been taken, such as increasing the contact area between the discharge field and the exhaust gas or promoting turbulence in the exhaust gas, nitrogen oxides NO.
There is a possibility that the dissociative removal of X will be insufficient.

The present invention has been made in view of the above points, and by disposing positive and negative electrodes alternately in the exhaust passage, the discharge field is multi-layered and the exhaust gas is made turbulent. By increasing the contact area between the field and the exhaust gas, nitrogen oxides (NOx) are
It is intended to increase the dissociative removal effect of. The purpose is to

(Means for solving the problems) In the present invention, as means for solving the above problems,
In the exhaust passage through which exhaust from the engine flows, a large number of discharge electrodes are arranged alternately in positive and negative directions in the exhaust flow direction, and conductive wires are installed that cross these electrodes in a direction perpendicular to the exhaust flow direction. It is supported on an insulator configured to allow the flow of exhaust gas.

(Function) In the present invention, the following effects can be obtained by the above means.

That is, in the exhaust passage, a multilayered silent discharge field is generated by the electrodes arranged in multiple layers in the exhaust flow direction (in the direction of exhaust flow), and the contact area between the exhaust and the discharge field is increased, and the discharge intensity is increased. This will greatly improve the dissociation and removal effect of nitrogen oxides (NOx) in the exhaust gas.Also, if the electrodes allow the exhaust gas to flow through the conductive wire that crosses the direction perpendicular to the exhaust gas flow direction, the By having the electrodes supported on an insulator constructed as shown in FIG. It is also possible to increase the contact area between the exhaust gas and the exhaust gas.The increase in the contact area as described above greatly contributes to improving the dissociation removal rate of nitrogen oxides NOx in the exhaust gas.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The exhaust purification device according to this embodiment is as shown in FIG.
Electrodes 3.3... provided in the discharge chamber 2a formed in the middle of the exhaust passage 2 from the engine 1, and a high voltage generator that applies high voltage to these electrodes 3, 3... 4. Each of the electrodes 3 is constructed by carrying a plurality of conductive wires 6, 6, . As shown in an enlarged view in FIG. 2, the ceramic foam 5 is a porous member having a large number of through holes 7, 7, . In other words, this ceramic form 5 allows the exhaust gas G to flow through due to the presence of the through holes 7.7. However,
These electrodes 3.3... are arranged at appropriate intervals such that the conductive wires 6.6... side face the flow direction of the exhaust gas G in the discharge chamber 2a, and the positive and negative electrodes are arranged at appropriate intervals. The high voltage generators are connected to the device 4 in an alternating manner. Thus, by applying a high voltage from the high voltage generator 4 to each electrode 3,3...
, 3... A silent discharge is generated between the two, and the exhaust G flowing through the discharge field generated by the silent discharge.
The nitrogen oxide NOx in the air contains 0. This results in dissociation into nitrogen and N. Note that oxygen after dissociation is 0. Due to the difference in affinity between molecules, it does not recombine with nitrogen N, but combines with carbon monoxide CO in the exhaust gas G to become harmless carbon dioxide CO2 and is discharged from the system, resulting in nitrogen oxidation. The harmless nitrogen N generated by the dissociation of NOx is discharged out of the system as is.

On the upstream side of the discharge chamber 2a, there is a device for detecting concentration fluctuations of DRY 5OOT (i.e., carbide, etc.) in particulates (i.e., fine particulate discharged substances) contained in the exhaust gas G flowing in the exhaust passage 2. A current detector 8 is attached. The current detector 8 has its detection terminals 8a,
By exposing terminal 8 a into the exhaust passage 2, it serves to detect variations in the conductivity of the exhaust G between these detection terminals 8 a, 8 a. DRY 5 is highly conductive in
It represents the concentration fluctuation of OOT. It is a well-known fact that there is a correlation between the concentration fluctuations of DRYSOOT in the exhaust gas G and the concentration fluctuations of nitrogen oxide NOX. Therefore, by detecting the conductivity variation by the current detector 8, the concentration variation of nitrogen oxide NOx in the exhaust gas G is detected.

Therefore, in this embodiment, the current fluctuation detected by the current detector 8 is amplified by the amplification means 9, and then fed back to the power control means 10, and the current fluctuation detected by the current detector 8 is fed back to the power control means IO.
The output voltage of the high voltage generator 4 is controlled by. In this way, the detected value of the current detector 8 (in other words, the concentration of nitrogen oxide NOx in the exhaust gas G)
The applied voltage by the high voltage generator 4 can be controlled in accordance with this, and the intended purpose of dissociating and removing nitrogen oxides NOx can be achieved by silent discharge with the minimum necessary power consumption. .

Next, the operation of the exhaust purification device according to the illustrated embodiment will be explained.

Exhaust gas G generated by the operation of the engine 1 passes through the exhaust passage 2 and reaches the discharge chamber 2a.
Electrode 3.3 to which high voltage is applied by high voltage generator 4
...A discharge field is generated by silent discharge in between. Therefore, the harmful nitrogen oxide NOx contained in the exhaust gas G flowing into the discharge chamber 2a is dissociated into oxygen O7 and nitrogen N by the action of the discharge field. The dissociated oxygen O1 does not recombine with nitrogen N due to the difference in affinity between molecules, but instead combines with carbon monoxide CO in the exhaust gas G to become harmless carbon dioxide CO1 and is discharged from the system. be done. In this way, the harmless nitrogen N generated by the dissociation of the nitrogen oxide NOX is discharged out of the system as is.

In the case of this embodiment, the discharge field in the discharge chamber 2a becomes a multilayer discharge field generated by the electrodes 3, 3, . . . arranged in multiple stages in the exhaust flow direction.
The contact area between the exhaust G and the discharge field is large because the exhaust G becomes turbulent due to the presence of a large number of through holes 7.7 formed in the insulator (i.e., ceramic foam) 5. is greatly increased, greatly contributing to the promotion of dissociation of nitrogen oxides NOx.

Further, when the electrode 3 in this embodiment is configured such that the ceramic foam as the insulator 5 supports the conductive wires 6.6, the assembly of the electrode 3 to the discharge chamber 2a and the electrode 3.3. ...It is extremely easy to ensure the stability of the spacing between the two.

In addition to the electrodes 3 shown in FIG. 1, the electrodes 3 in the above embodiment include conductive wires 6.6...・A conductive N wire 6 arranged in a mesh pattern, or as shown in FIG.
It is also possible to adopt a device with a . In short, the electrode 3 may be constructed by carrying a conductive wire 6 that crosses in a direction perpendicular to the exhaust gas flow direction on an insulator 5 configured to allow the flow of the exhaust gas G. Note that a coiled wire may be used as the conductive wire 6, and in that case, the discharge intensity increases because the discharge surface area increases. Furthermore, it is desirable to prevent noise generation by constructing the high voltage generating section with a metal material and grounding it, and constructing the lead wire portion with a shield wire.

It goes without saying that the present invention is not limited to the configuration of the above-described embodiments, and that the design can be changed as appropriate without departing from the gist of the invention.

(Effects of the Invention) As described above, according to the present invention, when a large number of discharge electrodes arranged alternately in positive and negative directions in the exhaust gas flow direction are arranged in the exhaust passage through which exhaust gas from the engine flows, both These electrodes are constructed by supporting conductive wires that cross in a direction perpendicular to the exhaust gas flow direction on an insulator configured to allow exhaust gas flow. The arranged electrodes generate a multi-layered silent discharge field, and the electrodes also promote turbulence in the exhaust, increasing the contact area between the exhaust and the discharge field, and increasing the discharge intensity. This has the excellent effect of greatly improving the dissociation and removal effect of nitrogen oxides (NOx) in the exhaust gas.

In addition, since the electrode is constructed by carrying a conductive wire that crosses in a direction perpendicular to the exhaust flow direction on an insulator configured to allow the flow of exhaust gas, it is easy to assemble the electrode into the exhaust passage. This also has the effect of improving the properties and ensuring the stability of the spacing between the electrodes.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the outline of an engine exhaust purification device according to an embodiment of the present invention, and FIG. The enlarged surface view, FIGS. 3 and 4 are a partial front view and a front view showing two variations of the electrode. 1... Engine 2... Exhaust passage 3... Electrode 5... Insulator 6... Conductive wire G.・・・・・・Exhaust Figure 4

Claims (1)

[Claims] 1. A large number of discharge electrodes are arranged in an alternating positive and negative direction in the exhaust flow direction in the exhaust passage through which the exhaust from the engine flows, and these electrodes cross in a direction perpendicular to the exhaust flow direction. 1. An engine exhaust gas purification device comprising a conductive wire supported on an insulator configured to allow exhaust gas flow.