JPS62139915A - Exhaust gas filter - Google Patents

Abstract

PURPOSE:To reduce the pressure loss and to prevent the excessive temperature rise by making the inlet diameter of an exhaust gas path of an exhaust gas filter employing a honeycomb structure of porous ceramic larger than the inner diameter of an inlet exhaust gas path while tapering the inlet section. CONSTITUTION:Closed sections 4, 5 are provided alternately at the cell end sections of a honeycomb structure where plural cells 2 are formed with porous ceramic. The inlet diameter at the inlet section 7 of an inlet exhaust gas path 6 in the honeycomb structure is made larger than the inner diameter of said path 6. Furthermore, the inlet section 7 is tapered. Since the exhaust gas at the inlet section will flow in while the stream line thereof being bent smoothly, the pressure loss is reduced. Since the soot in the exhaust gas will accumulate at the inlet section uniformly to the cell wall of the inlet exhaust gas path, the exhaust gas filter can be regenerated easily, resulting in prevention of excessive temperature rise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention collects particulate matter (hereinafter referred to as soot) emitted from, for example, a diesel engine, and burns the collected soot to remove air from the diesel engine. The present invention relates to an exhaust gas filter used as a device for reducing the amount of soot discharged into the air.

Conventional technology Diesel exhaust gas filters for collecting soot emitted from diesel engines include filters using metal wire mesh coated with alumina, ceramic foam filters with a porous structure using a foaming agent, and honeycomb-shaped filters. Ceramic monolith filters and the like have been devised. Among them, the soot dust collection efficiency is 90%.
% or more, honeycomb-shaped ceramic monolith filters with low pressure loss in exhaust gas through the filter are considered promising as filters for removing soot from exhaust gas.

A diesel exhaust gas filter made of a ceramic monolith filter has a honeycomb structure consisting of a large number of cells formed by extrusion molding using cordierite as a main component. The upstream and downstream cell ends of the no-nicum structure are made of a very low porosity material such as cement with a length of about 1
They are alternately occluded with 0 groups of materials. These upstream and downstream closures divide the cell into an inlet and an outlet exhaust gas passage. When the engine is operated, soot gradually accumulates and the pressure loss of the exhaust gas increases at the diesel exhaust gas filter, leading to a decrease in engine performance. Therefore, in order to maintain good engine performance, a method is used to regenerate the diesel exhaust gas filter by burning the soot once a certain amount of soot has accumulated. The soot deposited on the diesel exhaust gas filter is ignited by sparks in the exhaust gas or the ignition heater at the inlet end, and combustion spreads at the inlet end.
At the same time, it burns downstream within the cell.

Problems to be Solved by the Invention As shown in FIG. 2, in the diesel exhaust gas filter 10, part of the soot in the exhaust gas is deposited on the inlet end 11.
Most of the cell wall 14 of the inlet exhaust gas passage 13 in the cell 12
is deposited on. However, diesel exhaust gas filter 1o
In the inlet exhaust gas passage 13, the cell wall of the passage inlet portion 16 where the inlet blockage portion 16 is present has a higher rate of exhaust gas from the inlet exhaust gas passage 13 to the outlet exhaust gas passage 17 than the cell walls 14 of other portions in the same passage. Since the amount of gas passing through is small, the amount of soot deposited is extremely small. Still inlet exhaust gas passage 13
In the 0 inlet section 16, like other sections in the same passage, exhaust gas passes from the inlet exhaust gas passage 13 through the cell wall 14 to the outlet exhaust gas passage 17, and the amount of exhaust gas flowing inside the inlet exhaust gas passage 13 is small. Because there is no such thing as
The exhaust gas flow velocity in the longitudinal direction of the cell is at a maximum in this portion. Therefore, when the soot 18 deposited at the inlet end 11 is ignited and burned, and propagates into the inlet exhaust gas passage 13, sufficient combustion heat is not generated at the inlet part 16 of the passage, and the combustion heat is transferred to the exhaust gas. is taken away and the combustion temperature does not rise sufficiently, so combustion does not propagate within the passage, resulting in insufficient regeneration. If this is repeated several times, the amount of soot deposited in the same passage will continue to increase, and once a large amount of deposited soot is ignited, combustion will occur rapidly, and the temperature of the diesel exhaust gas filter will rise too much, causing the cell wall 14 to A melting problem arose.

Furthermore, when exhaust gas flows into the diesel exhaust gas filter 1°, the flow path cross-sectional area of the exhaust gas is reduced by the inlet blockage 16, and the flow of the exhaust gas that hits the inlet blockage 16 is directed toward the inlet end as shown by the arrow. Since the flow line is bent at a substantially right angle by the portion 11 and flows into the inlet exhaust gas passage 13, the pressure loss is large.

Means for Solving the Problems According to the present invention, the inlet diameter of the inlet exhaust gas passage is made larger than the inner diameter of the inlet exhaust gas passage.

Function: With the above configuration, the inlet diameter of the artificial exhaust gas passage is made larger than the inner diameter, so that the flow of exhaust gas at the inlet portion is gently bent and flows into the inlet exhaust gas passage. Furthermore, soot in the exhaust gas at the inlet portion where the streamlines are bent collides with the cell wall due to inertia and accumulates. As a result, soot is deposited uniformly from the inlet end to the cell wall of the inlet exhaust gas passage.

Embodiment An embodiment of the present invention is shown in FIG. 1 is a diesel exhaust gas filter, which is manufactured by the following method, for example. 20mm
30 parts by weight of alumina fiber cut as follows and 16 parts by weight of ceramic raw material powder are suspended in 300 parts by weight of water,
After adding an organic binder such as polyvinyl acetate to this mixed slurry, a corrugated sheet is created by bonding a corrugated sheet and a flat sheet in the same manner as in corrugated board manufacturing, and this is then bonded around the core. Wrap it around while doing so.
I created a nikum shape.

Next, each end of the honeycomb is coated with the following materials alternately so that the exhaust gas that has entered the cells 2 of one honeycomb passes through the cell wall 3 and is discharged after transferring to the other cell. Inlet and outlet closing parts 4 and 5 were formed by injecting the same amount into the cell.

This molded product was fired at 1260° C. in air to turn the ceramic fibers and ceramic raw material powder into a ceramic to form a honeycomb structure, and the inlet portion 7 of the inlet exhaust gas passage 6 was chamfered to obtain the exhaust gas filter 1.

Here, regarding the processing method of the inlet portion 7 of the inlet exhaust gas passage 6, there are other methods other than processing after firing as described above.
For example, there is no particular limitation, such as molding before firing and then firing.

Furthermore, the tapered shape does not have to be linear as shown in FIG. 1, but may be curved.

The material forming the closing part 4 is a paste made by calcining a sheet and adding 2 parts by weight of the crushed inorganic material, 0.1 part by weight of starch, and 2 parts by weight of water, and 0.1 part by weight of organic powder. Add 100% in powder form and stir to mix. By appropriately setting the porosity of the inlet closing part 4, exhaust gas can pass through, increasing the amount of soot deposited in the inlet part 7 and the inlet end, and smoothing the propagation of combustion. Good playback results can be obtained. Therefore, the inlet closing part 4
It is preferable to adjust the porosity to 40-90%. The porosity of the exhaust gas filter of this example was 60 cm.

In the figure, 8 indicates an outlet exhaust gas passage, 9 indicates accumulated soot, and arrows indicate the flow of exhaust gas.

The exhaust gas filter thus obtained was attached to the exhaust gas manifold of an engine and a regeneration test was conducted. Engine speed 124 rpm, torque 12 to 9.
After operating the engine for 3 hours at 500 m and accumulating soot, the engine was put into an idle state and at the same time ignited with an ignition heater to regenerate the engine. Combustion was completed in about 3 minutes and almost no soot remained. The above regeneration test was repeated 10 times, and then the exhaust gas filter was taken out, cut, and observed, but no cracks or melted parts were found anywhere.

When a similar regeneration test was conducted on a conventional exhaust gas filter, up to two times, even if ignition occurred at the inlet end, combustion did not propagate to the inlet exhaust gas passage, resulting in insufficient regeneration. During the third regeneration, soot was observed to be discharged to the outside, and when the exhaust gas filter was observed after the regeneration, a large number of cracks and melted parts were confirmed. Effects of the Invention The present invention is as described above. This configuration provides the following excellent effects: The flow of exhaust gas at the tapered inlet part of the inlet exhaust gas passage flows into the inlet exhaust gas passage with its streamline curved gently, so the pressure is reduced. Loss is small. Furthermore, soot in the exhaust gas at the inlet portion where the streamlines are bent collides with the cell wall due to inertia and accumulates. As a result, soot is deposited uniformly from the inlet end to the cell wall of the inlet exhaust gas passage, making it easier to regenerate the exhaust gas filter and eliminating damage caused by excessive temperature rise.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view of an exhaust gas filter according to an embodiment of the present invention, and FIG. 2 is a partial sectional view of a conventional exhaust gas filter. 1...Exhaust gas filter, 2...Cell,
3...mark cell wall, 4, 5...inlet, outlet closing part, 6...inlet exhaust gas passage, 7...inlet part, 8...・Exit exhaust gas passage, 9...
・Soot. Name of agent: Patent attorney Toshio Nakao (1 person)
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Claims (3)

[Claims] (1) A honeycomb structure in which a plurality of cells are formed of porous ceramics is provided with blocking parts alternately at the cell ends, and the inlet diameter of the inlet exhaust gas passage of the honeycomb structure is made larger than the inner diameter of the inlet exhaust gas passage. Exhaust gas filter. (2) The exhaust gas filter according to claim 1, wherein the inlet portion of the inlet exhaust gas passage is tapered. (3) The exhaust gas filter according to claim 1, wherein the porous ceramic is a fibrous ceramic as a main component.