JPH0533631A - Air cleaning device by electrostatic field - Google Patents

Abstract

PURPOSE:To provide a device for cleaning air by means of an electrostatic field, with an electrostatic condenser that is made so as to secure the insulability of an electrode part in particular. CONSTITUTION:Exhaust gas out of a diesel engine 12 is led into an electrostatic condenser 15 constituting an exhaust emission control device 11 via an inlet pipe 16, exhausted out of an outlet pipe 18, and it is made so as to form a swirl flow of exhaust gas around a discharge electrode 153 being set in the axial part, in a cylindrical electrode 151 of the condenser 15. Each of insulating supporters 19, 20 is installed at both ends of the cylindrical electrode 151. These insulating supporters 19, 20 are provided with insulators 192, 202 supporting an electrode rod 152 which supports each of outer pipes 191, 201 and the discharge electrode 153. In addition, each of inlet pipes 193, 203 being fed with clean air is installed in these outer pipes 191, 201 along each tangent of these pipes 191, 201, through which such a possibility that a swirl flow in reverse to an exhaust gas swirl flow is produced in these outer pipes 191, 201 and thereby the exhaust gas swirl flow might lead to the insulators 192, 202 is prevented from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air purifying device using an electrostatic field for separating particulate matter discharged from a diesel engine so that purified exhaust gas is discharged.

[0002]

2. Description of the Related Art For example, as a device for purifying exhaust gas from a diesel engine, a device has been considered in which particles (particulates) contained in exhaust gas are charged by an unequal electric field and the particles are aggregated. There is.

In such a device, an electrode to which a high voltage is applied to charge particles is set.
It is important to ensure the insulating property of the electrode portion. However, if particles in the air or the like adhere to the portion of the electrode portion that holds the insulating property, it becomes difficult to maintain the insulating property.

As means for ensuring the insulating property of such an electrode part, for example, a method of firing the adhered particles by heating the insulating part holding the electrode, or causing spark discharge on the surface of the high-voltage insulator to adhere A method of firing particles is known. However, such a method requires a new heating power source of even higher power. Further, in the case of using the spark discharge, the voltage is lowered during the discharge, and the particles are not sufficiently charged by the corona discharge. Therefore, the air purification effect may decrease.

In consideration of these points, for example, Japanese Patent Publication No. 62-62
As disclosed in Japanese Patent Laid-Open No. 49451/1992, it is considered to form an air curtain corresponding to the axial direction of the electrodes formed along the insulator. However, when the exhaust gas is flowing around the electrode due to the swirling flow, turbulence in the air flow also occurs inside the air curtain, particles adhere to the insulator part that holds the electrode, and May cause problems.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and even if exhaust gas is caused to flow by a swirling flow in a condenser device portion in which an electrode is set in a central shaft portion. In particular, it is an object of the present invention to provide an air purification device by an electrostatic field in which particles and the like in exhaust gas are not attached to an insulating holder portion that holds an electrode, and the insulating property is reliably ensured. ..

[0007]

In an air purifying apparatus using an electrostatic field according to the present invention, in an electrostatic condensing device having a cylindrical electrode having a discharge electrode set on a central shaft portion, the electrostatic electrode is provided in the discharge electrode. While introducing air to be purified so that a swirling flow is generated around the discharge electrode, a cylindrical insulating holder is provided coaxially in communication with the end of the cylindrical electrode,
An electrode rod that supports the discharge electrode is held by the insulating holder portion. Then, clean air is introduced into the insulating holder so that a swirl flow opposite to the swirl flow in the cylindrical electrode is generated in a laminar flow direction toward the cylindrical electrode.

[0008]

In the air purifying device thus constructed,
A swirl flow due to, for example, the exhaust gas is generated around the discharge electrode in the cylindrical electrode that constitutes the electrostatic coagulator, and a swirl flow due to clean air is also generated in the insulating holder coaxial with the cylindrical electrode. Is set in the direction opposite to the swirling flow in the cylindrical electrode. Therefore, the swirling flow generated in the cylindrical electrode is alleviated, and this swirling flow is surely prevented from entering the edge holder, and for example, particles in the exhaust gas are generated in the insulating holder, especially in the electrode. Adhesion to the holding portion is reliably prevented, insulation is ensured, and reliability is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an exhaust emission control device 11 for an automobile, in which fine particles contained in the exhaust gas of a diesel engine 12 (generally called particulates, carbon,
It shows a device for separating unburned fuel, fine particles mainly composed of polymer hydrocarbons such as oil) from the exhaust gas by utilizing electrostatic force.

The exhaust purification device 11 is installed behind a muffler 13 to which the exhaust gas of the diesel engine 12 is supplied. The output exhaust gas from the muffler 13 is purified by the purification device 11 via an inflow pipe 14. Is supplied to the inlet pipe 16 of the electrostatic aggregating device 15 constituting the.

The electrostatic aggregating device 15 is provided with a cylindrical electrode 151 formed in a cylindrical shape by a conductor, and a central axis portion of the cylindrical electrode 151 is supported by an electrode rod 152 and has a plurality of needle electrodes on the outer circumference. The discharge electrode 153 is set so as to project toward it. Then, a high voltage is applied and set from the high voltage generator 17 between the discharge electrode 153 and the cylindrical electrode 151 of the aggregating device 15.

Here, the inlet pipe 16 to which the exhaust gas is supplied
Is at one end of the cylindrical electrode 151 as shown in FIG.
The cylindrical electrode 151 is opened so as to have an axis parallel to the tangent line, and the other end of the cylindrical electrode 151 is also formed with an outlet pipe 18 having an axis parallel to the tangent line. Therefore, when the exhaust gas is introduced from the inlet pipe 16 and the exhaust gas is discharged from the outlet pipe 18, a swirling flow that surrounds the outer circumference of the discharge electrode 153 is generated inside the cylindrical electrode 151. It has become.

Insulation holders 19 and 20 are integrally provided at both ends of the cylindrical electrode 151. These insulation holders 19 and 20 respectively include cylindrical outer tubes 191 and 201 coaxial with the cylindrical electrode 151, and these outer tubes 191 and 201 are configured to communicate with the cylindrical electrode 151. And the ends of each of these outer tubes 191 and 201 are
The ends of the electrode rod 152 supporting the discharge electrode 153 are fixed and held by the insulators 192 and 202, respectively, which are closed by the insulators 192 and 202.
Are insulated from and supported by the cylindrical electrode 151.

The outer pipes 191 and 201 of the insulation holders 19 and 20, respectively, are provided with clean air introducing pipes 193 and 203 communicating with the air pump 21, and are introduced from these introducing pipes 193 and 203, respectively. The clean air creates a laminar swirl flow in the outer tubes 191 and 201. In this case, the direction of the swirling flow of the clean air is set to be opposite to the direction of the swirling flow of the exhaust gas formed in the cylindrical electrode 151.

The exhaust gas taken out from the outlet pipe 18 of the electrostatic agglomerator 15 is guided to the cyclone 22, and the exhaust gas from which the fine particles in the exhaust gas have been separated is discharged from the exhaust pipe 24 to the outside. Here, the cyclone 22 separates fine particles and exhaust gas by centrifugal force, and the separated fine particles are accumulated in the stocker 23.

Here, the amounts of clean air introduced by the introduction pipes 193 and 203 into the outer pipes 191 and 201 constituting the insulation holders 19 and 20 are such that the following conditions are satisfied.

A) The axial flows of the cylindrical outer tubes 191 and 201 constituting the insulating holders 19 and 20 toward the aggregating device 15 are made laminar. b) The rotation speed of the clean air is suppressed so that the circulating flow due to the swirling rotation speed of the exhaust gas in the cylindrical electrode 151 is not generated.

For the conditions shown in a), the outer tube 19
Representing 1 and 201 as a cylindrical tube, the flow velocity of the air flowing in the axial direction is V, the air density is ρ, the viscosity of the air is μ, and the inner diameter of the cylindrical tube is d. Be Re = (ρdV) / μ <2100.

With respect to the condition b), when the exhaust rotation speed is Ve and the clean air speed is Vp, the stirring Reynolds number is Rev = {(Ve-Vp) Pd} / πμ <100. To be taken.

For example, a cylindrical electrode 151 made of a SUS tube having an inner diameter D of 110 mm and a length L of 500 mm has an inner diameter of 50 mm.
When the outlet pipe 18 of the
It is rotated at 3000 rpm at 31 cc and the exhaust gas amount is 136146 cc at room temperature of 25 ° C and exhaust temperature of 200 ° C.
/ Sec.

In this case, the sectional area of the outlet pipe 18 is 19.5 cm.
^2, therefore the exhaust gas swirl velocity Ve of the cylindrical electrode 151 becomes 67.4M / sec.

If the outer tube 191 of the insulating holder 19 having an inner diameter of 50 mm and a length of 100 mm is attached to the electrostatic coagulation device 15 having such a cylindrical electrode 151, the swirling speed Vr given to the outer tube 191 is , The swirl velocity Ve in the cylindrical electrode 151 is regarded as a forced vortex, and can be obtained by the following equation multiplied by the influence coefficient K obtained by the experiment. Vr / d = K · Ve / D = 6.3 m / sec Here, the density ρ and viscosity μ of air at 200 ° C. are respectively ρ = 0.74 × 10 ⁻³ (g / cc) μ = 2 Since it is 0.5 × 10 ⁻⁴ (poise), the stirring Reynolds coefficient Rev of the swirling flow in the outer tube 191 of the insulating holder 19 is “1969”, and “Rev>
A circulation flow occurs at 100 ".

Here, the circulation flow means, as shown in FIG. 3, from the partition wall 154 of the cylindrical electrode 151 provided by the swirling flow to the insulator 192 portion of the outer tube 191 of the insulation holder 19 and the outer tube 191.
It means the flow that returns from the center to the original turning position.

In order to prevent such a circulating flow, clean air is introduced into the outer tube 191 of the insulating holder 19 via the introduction tube 193. The direction of this air introduction is the exhaust gas swirling in the cylindrical electrode 151. The flow is set in the direction opposite to the flow, and the flow rate is set so as to satisfy the above conditions a) and b).

First, in order to satisfy the condition of a), the density ρ and the viscosity μ of clean air are “ρ = 1.3 × 10”, respectively.
^-3 (g / cc) "and" μ = 1.7 × 10 ^-4 (poise) "
Therefore, “Re = ρdVp / μ <2100”, and the flow rate of the clean air in the outer tube 191 is “Vp <54.4”.
m / sec ”.

When the flow rate of the clean air in the outer pipe 191 is Q and the cross-sectional area of the introduction pipe 193 is S, Q = SVp <63.9 liter / min. Therefore, it was decided to flow "Q = 50 liters / minute" of clean air.

At this time, in order to satisfy the condition of b), the introduction pipe 19
The velocity Vp of the air flowing from 1 is determined based on the following conditions. That is, Rev = {(Ve-Vp) .rho.d / .mu..pi. <100, so that "Vp> 6.1 m / sec", where da is the inner diameter of the clean air introducing pipe 193, "(da ²
.pi. / 4) Vp = Q ", so that" da <1.4
8 mm ". Therefore, it suffices to use an introduction tube having an inner diameter of 1.26 mm. The insulator holding the electrode rod 152 is used.
The position of 192 was decided to be more than 2 cm away from the position of the introduction pipe 193.

Explaining the operation of the exhaust gas purification device 11 thus configured, the exhaust gas containing fine particles discharged from the diesel engine 12 passes through the muffler 13 and the inlet pipe, and the cylindrical electrode 151 of the electrostatic coagulation device 15 is provided. Will be introduced in. The exhaust gas introduced into the cylindrical electrode 151 is swirled in the cylindrical electrode 151. In this case, the centrifugal force of the swirling flow facilitates the particles in the exhaust gas to come into contact with the inner peripheral surface of the cylindrical electrode 151.

When a negative high voltage is applied to the discharge electrode 153 in such a state, an electrostatic field is formed between the cylindrical electrode 151 and the discharge electrode 153, and the discharge electrode 153 to the inner peripheral surface of the cylindrical electrode 151. A corona discharge is generated toward.

Due to this corona discharge, fine particles in the exhaust gas are negatively charged and collide and accumulate on the inner peripheral surface of the cylindrical electrode 151, and the particle diameter grows on this inner peripheral surface, so-called electrostatic aggregation. Happens. The diameter of fine particles in the inflowing exhaust gas is about 0.1 to 7 μ before flowing into the aggregating device 15.
m is 50 to 100 μ due to electrostatic aggregation
grows to m.

Here, the insulators 192 and 202 of the insulation holders 19 and 20, respectively, hold the electrode rod 152 and the cylindrical electrode 151.
The particles are electrically insulated from each other, but if particles adhere to the insulators 192 and 202, leakage may occur. However, by introducing clean air from the introduction pipes 193 and 203, a swirling flow opposite to the swirling flow in the cylindrical electrode 151 is generated in the outer pipe.
When it occurs in 191 and 201, the circulation flow due to the exhaust flow does not occur, and the laminar flow along the axis of the outer tube occurs.

That is, an air curtain is formed on the insulators 192 and 202 so that fine particles in the exhaust gas are not adhered, and the insulation between the electrode rod 152 and the cylindrical electrode 151 is reduced. It is surely stopping.

The fine particles whose particle size has grown in the electrostatic agglomerator 15 flow into the cyclone 22 and are separated by the centrifugal force. The separated fine particles are sent to the stocker 23 and are separated and cleaned. The exhaust gas is discharged into the atmosphere through the exhaust pipe 24.

The results of experiments conducted on the thus constructed apparatus will be shown. First, in the experiment, as shown in FIG. 4, an exhaust flow was blown by a blower 31 at 5700 liters / minute, and an electrostatic condensation device 15 having an inner diameter of 110 mm and a length of 500 mm was used, and an inlet pipe 16 and an outlet pipe having an inner diameter of 50 mm were used. Air was introduced at 18 and exhausted. An insulating holding tube 19 having an inner diameter of 50 mm and a length of 90 mm was installed, and an introducing tube 193 was installed at a position 20 mm away from the end of the holding tube 19. In this case, the swirling flow by the clean air introduced from the introducing pipe 193 is set to be in the same direction as the swirling flow generated in the electrostatic coagulation device 15 part, or is set in a different direction. I set it to the target.

Table 1 shows the result of observing the degree of deflection of the flag 32 set inside the insulating holder 19. Here, the velocity of the air introduced from the introduction pipe 193 is 1
Shown in liters per minute, test A and test B
The amount of exhaust gas introduced into the electrostatic coagulator 15 is 5.7 m ³ /
Set to minutes. Further, the backflow rate shown here is the probability that the flag swings in the direction opposite to the direction of the air introduced from the introduction pipe 193.

The flag 32 is provided at positions 30 mm, 60 mm, and 90 mm from the insulator portion of the end surface portion of the insulation holder 19,
Attach at -30mm, 0mm, 30mm from the axis center,
The result of observing the direction of the flag 32 for about 5 minutes is shown.

[0037]

[Table 1]

As a result of such an experiment, the swirl flow of the clean air is insulated in the direction opposite to the exhaust swirl flow in the electrostatic coagulation device 15.
It was confirmed that the backflow rate became “0” especially in the state where the clean air flow rate was 50 liters / minute.

Next, an example in which an experiment is actually performed using an engine will be described.

In this experiment, a 2200 cc diesel engine was used, and this engine was rotated at about 900 rpm. An electrostatic coagulator having an inner diameter of 110 mm and a length of 500 mm was provided with an inlet pipe and an outlet pipe having an inner diameter of 50 mm. Exhaust gas is allowed to flow in and out through it.

Then, in the first experiment, as shown in FIG.
The insulating holder 19 having a length of 90 mm and a length of 90 mm is provided, and the insulating holder 19 has a structure in which clean air is not introduced. In the second experiment, as shown in (B) of the figure, the inner diameter was 50 m.
An insulating holder 19 having a length of 90 mm and a length of 90 mm is provided at the end of the electrostatic agglomerator 15, and an introducing pipe 193 having an inner diameter of 1.26 mm is provided at a position about 20 mm away from the end of the insulating holder 19. Then, the clean air introduced from the introduction pipe 193 generates a swirl flow opposite to the exhaust swirl flow generated in the electrostatic coagulation device 15, and the clean air was flowed at about 50 liters / minute.

When the first and second experiments as described above were carried out, in the first experiment shown in FIG. 7A, fine particles adhered to the insulator 192 on the end surface of the insulating holder 19 after about 1 hour,
Due to the fine particles, a current leak came to occur between the outer tube 191 and the electrode rod 152.

On the other hand, in the second experiment shown in FIG. 7B, the insulator 192 of the insulation holder 19 is retained even after about 6 hours.
No adhesion of fine particles is observed at the portion, and a current leakage with the electrode rod 152 does not occur.

In the above-described embodiments, the insulating property of the discharge electrode 153 of the electrostatic agglomeration device 15 is ensured, but electrostatic dust collection, plasma decomposition of harmful components of exhaust gas,
It can also be applied to other purposes using high voltage such as an ozonizer.

In the above embodiments, the insulating holder
Introducing pipe along the tangent of each of the outer pipes 191 and 201 of the 19 and 20
193 and 203 are provided so that swirl flow is generated in the outer tubes 191 and 201 by the clean air introduced from the introduction tubes 191 and 201.

However, as shown in FIG. 6, a clean air introduction pipe 195 is set parallel to the electrode rod 152 on the insulator 192 set on the end face of the insulation holder 19 and this introduction pipe 195 is provided.
Alternatively, clean air may be blown into the electrode rod 152 in parallel. However, in this case, the outer tube 19
The guide 196 for swirling the air flow is set at a position where the blown clean air hits the inside of 1.

Further, as shown in FIG. 7, a clean air passage 197 may be provided in the central axis portion of the insulating holder 19. In this case, a plurality of hollow needles 198 for blowing clean air are formed on the outer circumference of the air passage 197 along the tangent line of the peripheral surface of the air passage 197. Then, a swirling flow is generated in the outer tube 191 by the air flow ejected from the hollow needles 198.

Here, the amount of clean air that flows in to generate a swirling flow in the insulating holders 19 and 20 is controlled so as to be proportional to the amount of exhaust gas that is generated in the engine. May be reduced. Therefore,
It is also possible to use an air pump that uses the rotation of the engine as a drive source, and it is also configured to detect the number of revolutions of the engine and variably control the amount of clean air according to this number of revolutions. Good.

[0049]

As described above, according to the air purifying apparatus by the electrostatic field according to the present invention, when the gas containing various fine particles is treated by the swirling flow generated in the electrostatic coagulating apparatus,
In this electrostatic coagulation device, it is possible to reliably prevent the discharge electrode section from breaking the insulation state by fine particles, and the insulation property of the electrode section to which a high voltage is applied and set is surely ensured, and the reliability is improved. For example, an air purifying device that has excellent properties and that treats exhaust gas of a diesel engine is configured.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an air cleaning device according to an embodiment of the present invention.

2A and 2B are views showing the insulation holder portion of the above embodiment taken out, where FIG. 2A is a sectional view and FIG. 2B is a side view.

FIG. 3 is a diagram illustrating a circulating flow of an insulating holder portion.

FIG. 4 is a view showing an apparatus for testing the effect of the above-mentioned embodiment.

5 (A) and 5 (B) are views showing the configuration of an apparatus for comparative experiments of the effects of the present invention.

FIG. 6 is a configuration diagram illustrating another embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating still another embodiment of the present invention.

[Explanation of symbols]

11 ... Exhaust gas purification device, 12 ... Diesel engine, 15 ... Electrostatic coagulation device, 151 ... Cylindrical electrode, 152 ... Electrode rod, 153 ...
Discharge electrode, 16 ... Inlet tube, 17 ... High voltage generator, 18 ... Outlet tube, 19, 20 ... Insulation holder, 191, 201 ... Outer tube, 192, 202
… Insulators, 193, 203… Inlet pipes, 21… Air pumps, 24
…Exhaust pipe.

Claims (1)

Claim: What is claimed is: 1. A cylindrical electrode and a discharge electrode set on a central axis portion of the cylindrical electrode are provided, and a high voltage is set to be applied between the discharge electrode and the cylindrical electrode. Electrostatic flocculation device and inlet and outlet pipes of air to be purified open-connected to the cylindrical electrode so that a swirling flow in a specified direction is generated around the discharge electrode of the electrostatic flocculation device. And a cylindrical insulating holder formed at the end of the cylindrical electrode of the electrostatic aggregating device in a state of communicating with this cylindrical electrode, and having an insulator set on the end face thereof to support the electrode rod holding the discharge electrode. And a clean air which is opened and communicated with the inside of the insulation holder and generates a swirl flow in the direction opposite to the swirl flow in the direction of the cylindrical electrode of the electrostatic aggregating device. Equipped with an air introduction pipe for introducing Flow rate of clean air introduced from the air inlet tube, said insulating holder inside air purification device according to an electrostatic field flow in the axial direction is characterized by being configured to be a laminar flow.