JPH0153105B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that electrically collects soot particles contained in exhaust smoke emitted from an internal combustion engine and burns and removes them.

Generally, the exhaust smoke emitted from internal combustion engines, especially diesel engines, contains many soot particles with a diameter of 2 microns or less. If, for example, a conventional centrifugal separator is used as a device for capturing this substance, the exhaust resistance of the device will be extremely large, and the device will also be large. Furthermore, if a filter device is used to collect the particles, the filter may become clogged with the collection, resulting in an increase in back pressure. Furthermore, in addition to these methods, a method of promoting the oxidation of soot using a catalyst is also considered, but at present no catalyst with sufficient low-temperature activity has been found.

On the other hand, there is electric dust collection, in which soot particles charged by corona discharge are deposited on the inner surface of a cylindrical dust collecting electrode using Coulomb force caused by an electric field. this is,
In general, it is possible to collect even extremely fine particles (0.1 microns) with high collection efficiency, and it is said that it can be used in environments with temperatures and pressures comparable to those of automobile exhaust smoke. Furthermore, it has many advantages such as low power consumption and extremely low ventilation loss. However, the disadvantage is that re-scattering phenomena and reverse ionization phenomena may occur due to the accumulation of soot on the dust collection electrodes, and there is also a risk of current leakage due to fouling of the interelectrode insulator and failure to treat the collected dust. There is a problem to be solved.

The exhaust gas dust collector of the present invention eliminates the above-mentioned drawbacks and collects and burns only a large amount of fine particles such as soot. That is, the dust collector of the present invention includes a flue through which exhaust gas discharged from an internal combustion engine passes, a dust collection chamber in which part of the inner wall forming the flue is a perforated wall, and a dust collection chamber. It consists of a planar dust collecting electrode and igniter installed in the flue, and a counter electrode installed in the flue.The soot, etc. in the exhaust gas passing through the flue is electrostatically collected in the dust collection chamber and burned by the igniter. It is characterized by allowing

The following will explain the embodiments shown in the drawings.

The figure shows a cross-sectional view of an embodiment of the invention. This device consists of an outer cylinder 1 made of metal or conductive material that also serves as a dust collection electrode, a perforated ceramic tube 2 installed inside the outer cylinder 1, and a center electrode 3 placed in the center of the ceramic tube 2. A flue 4 is formed on the inner wall surface of the ceramic tube 2, and a dust collection chamber 5 is formed on the inner wall surface of the outer cylinder 1 and the outer wall surface of the ceramic tube 2. An ignition device 6 made of an electric resistance heating wire is provided in the dust collection chamber 5. An exhaust gas inlet 11 is located near one end of the outer cylinder 1.
is open, and the inflow pipe 12 is fixed orthogonally thereto. The other end of the outer cylinder 1 serves as an exhaust gas outlet 13, and an outflow pipe 14 is fixed thereto. The ceramic tube 2 extends along almost the entire inner wall surface of the outer cylinder 1, and its both ends are flared into flanges and abut against the inner wall surface near both ends of the outer cylinder 1. Furthermore, a large opening 21 is formed in the ceramic tube 2 at a portion facing the exhaust gas inlet 11 of the outer cylinder 1. and,
A hole 22 with a diameter of several millimeters is formed over the entire surface between this opening 21 and the other end. The dust collection chamber 5 is connected to the flue 4 through these many holes 22. A flange 17 is fixed to the end of the outer cylinder 1 near the exhaust gas inlet 11 with bolts 18, with a disk-shaped ceramic partition wall 16 having a center hole 15 in between. The inside of the flange 17 is a recess, and an air chamber 20 is formed between the flange 17 and the partition wall 16. Also, the center of the flange 17 has a screw hole 1.
9 is formed, and the center electrode 3 is screwed here. The center electrode 3 consists of a rod-shaped electrode member 31 having a large number of protrusions formed on its surface, a ceramic member 32 covering the other end, and a terminal 33 at the tip thereof. A flange 17 is provided on the outer surface of the ceramic member 32.
A metal threaded portion 34 that engages with the center threaded hole 19 of the
is fixed. The center electrode 3 is fixed to the flange 17 and is connected to the air chamber 20 and the center hole 1 of the partition wall 16.
5 and is placed in the center of the flue 4. An annular slit is formed between the inner wall surface of the central hole 15 of the partition wall 16 and the outer surface of the ceramic member 32 of the center electrode 3, and air is ejected from the air chamber 20 into the flue 4 through this gap. Note that the air in the air chamber 20 is supplied from the outside through the air supply port 23 of the flange 17.

The exhaust gas dust collector of this embodiment has the above configuration. Exhaust gas from the internal combustion engine enters the flue through the inflow pipe of this device, and an electrostatic voltage is applied between the electrode member 31 of this electrode and the inner wall surface of the outer cylinder 1, which is the opposite electrode, with the center electrode 3 as the negative electrode. Then, the soot contained in the exhaust gas is charged by the corona discharge generated between the electrodes, and is attracted to the opposite electrode by the Coulomb force, and the ceramic tube 2 forming the peripheral side of the flue 4 is
It enters the dust collection chamber 5 through the hole, and enters the outer cylinder 1 which is the opposite electrode.
Adheres to the inner wall surface of the The exhaust gas from which soot and the like have been removed is discharged from the flue 4 to the outside through an outflow pipe. Further, the soot and the like collected in the dust collection chamber 5 are intermittently ignited by an ignition device 6, burned, and removed from the dust collection chamber.

In this device, since the dust collection chamber 5 and the flue 4 are separated by the ceramic pipe 2, there is little possibility that the soot and the like collected in the dust collection chamber 5 will be scattered again by the exhaust gas passing through the flue 4. Further, since the dust collection chamber 5 and the counter electrode are formed along the inner circumferential wall forming the flue 4, the dust collection area is wide and the dust collection efficiency of soot and the like is accordingly high. Further, since the inner circumferential wall forming the flue 4, together with the ceramic tube 2 and the ceramic partition wall 16, are all made of non-conductive material, there is little risk of electrical leakage. In addition, soot and the like are blown away by air ejected from the annular slit between the center hole 15 of the partition wall 16 and the center electrode 3.
Soot and the like are less likely to adhere to the surface of the center electrode 3. For this reason, electrical leakage due to soot adhesion is more effectively prevented.

In this device, a cylindrical outer tube is used as the outer tube 1, but other shapes such as an angular shape and an elliptical cross section can be used. In addition, a catalyst layer of platinum-20% palladium or the like is formed on the wall surface forming the flue 4 and the wall surface forming the dust collection chamber 5, so that soot, etc. adhering to those surfaces is combusted by the catalytic action. You can also do it.

The voltage between the center electrode 3 and the counter electrode is preferably several kilovolts or more. The voltage is preferably a direct current voltage, but it can also be a pulsed voltage if the soot can be partially combusted in the soot channel.

In order to confirm the effectiveness of this device, we attached it to the exhaust manifold of an automobile diesel engine and conducted a performance test against smoke emitted from the engine.

The diesel engine used in the experiment had a displacement of
2188c.c., and conducted experiments on the bench.
The operating conditions are 2000rpm and 6kgm load.
The power sources used were DC and pulse waveform. The voltage applied to the center electrode is -15KV for both
In the experiment using a pulse power supply, 500 pulse voltages with a width of 0.3 ms were applied per second.

Note that the electrode with the inner wall surface of the outer cylinder 1 as a counter electrode was grounded. Air was then supplied to the air chamber 20 at a rate of 50 per minute.

Experiments were conducted using this device under the conditions described above, the amount of soot and other dust was measured, and the effectiveness of this device was investigated. The method for measuring the amount of dust is to introduce the exhaust gas from the engine to this device, and then collect it from inside the exhaust pipe for 20 minutes.
The exhaust gas was sampled for 10 minutes, the gas was filtered, and the weight of the trapped dust was measured. As a result, when voltage was applied, compared to when no voltage was applied, in the case of direct current, it was 40 to 50% by weight, and when using a pulse power source, it was 30% by weight.
A weight reduction of ~40% by weight was observed, and furthermore, it was found that the dust particles such as soot deposited on the dust collection electrode were completely burned in the combustion treatment tube, allowing continuous operation.

In addition, if an alumina tube is used as the ceramic tube 2 and platinum-20% palladium is vapor-deposited in the form of islands on the dust collection chamber side, the accumulated soot will be affected by its catalytic action if the temperature of the alumina surface exceeds 400℃. It was also found that combustion occurred without any ignition operation.

[Brief explanation of drawings]

The figure is a sectional view of an exhaust gas dust collector according to an embodiment of the present invention. In the figure, numeral 1 is an outer cylinder, 2 is a ceramic tube, 3 is a center electrode, 4 is a flue, and 5 is a dust collection chamber.

Claims (1)

[Scope of Claims] 1. A flue through which exhaust gas discharged from an internal combustion engine passes, a dust collection chamber in which part of the non-conductive inner wall forming the flue is a perforated wall, and a dust collection chamber. A planar dust collection electrode and igniter installed indoors, a long and thin rod-shaped discharge electrode installed in the center of the flue parallel to its axis, and air around the electrode with a diameter larger than that of the electrode is blown out. 1. An exhaust gas dust collection device comprising an annular slit, which electrostatically collects fine particles such as soot in the exhaust gas passing through a flue into a dust collection chamber, and burns them using an ignition device. 2. The exhaust gas dust collector according to claim 1, wherein the ignition device is a catalyst layer disposed on the inner wall of the dust collection chamber.