JPH08151919A - Particulated trap for diesel engine - Google Patents

Abstract

PURPOSE: To provide a high pressure difference recovery rate with a low output heater by providing a face-like regenerating heater opposite the exhaust gas flow-in face of a filter, specifying its output and making short the filter until a filter heating amount per unit area by the heater reaches a specified value. CONSTITUTION: Cylindrical Filters 1 and 2 of different diameters are concentrically combined together, an electric heater 3 is disposed therebetween and a filament 10 constructed in this manner is placed in a canister 11. The heater 3 is formed by punching an Inconel thin plate and machining this in a cylindrical form by adjusting its resistance. In this case, the output of the heater 3 is set to 400W or below and the heater 3 and the filters 1 and 2 are reduced in their lengths until a filter heating amount per unit area by the heater 3 becomes 0.60W/cm<2> or over. Then, reduction in the surface areas of the filters 1 and 2 is compensated for by an increase in filter thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate trap for collecting and removing fine particles (particulates) such as carbon in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Exhaust gas from an automobile is one of the major causes of air pollution, and a technique for removing harmful components contained in the exhaust gas is extremely important.

Particularly in diesel engine vehicles, the removal of fine particles (particulates) mainly composed of NOx and carbon is an important issue.

In order to remove these harmful components, EG
Although R (exhaust gas recirculation) is applied, the fuel injection system is improved, and efforts are being made on the engine side, there is no fundamental deciding factor, and an exhaust trap is installed in the exhaust passage to make particulates. It is proposed to collect by trap and remove by post-treatment. To date, this post-treatment method is considered to be the most practical and is being studied.

The post-treatment of the collected particulates is best burned for repeated use of the trap. As a method of regenerating the particulate trap by the combustion, particulate incineration using a light oil burner is also considered, but from the viewpoint of safety and ease of control, combustion regeneration by an electric heater is the most promising at present. A particulate trap that actually employs the electric heater is (1) JP-A-5-22290, (2) JP-A-6-257422, (3) The same as JP-A-6-26472.
It is proposed in Japanese Patent Publication No. 2 and the like.

[0006]

[Problems to be Solved by the Invention]
The publication of (2) mentions the regeneration status when using an electric heater of 700 W, and the publication of (3) mentions 800 W. However, the particulate trap adopting such a high output heater is used for the current automobile electrical equipment. Considering the capacity of the battery, alternator, relay, etc., its use is not allowed unless it is a large vehicle such as a truck or bus. In the case of medium-sized and small-sized vehicles, it is necessary to reduce the power consumption of the heater to perform regeneration because the capacity of the on-board battery is limited.

The problem in this case is how to increase the combustion efficiency of the collected particulates.
For example, if the conventional trap is used and only the heater output is lowered without changing the other specifications, the particulates will not burn well due to insufficient heating, and the recovery rate of the differential pressure between the filter inlet and outlet will increase due to particulate collection. It becomes low and the filter performance deteriorates.

Further, if the power consumption is reduced by a method of reducing the size and capacity of the conventional particulate trap by some percentage, there arises a problem in the differential pressure life of the filter and the particulate collection efficiency.

The particulate trap is required not only to have a high differential pressure recovery rate of the filter, but also to have a long differential pressure life and an excellent particulate collection efficiency. Therefore, these performances are maintained. It is necessary to devise to reduce the power consumption of the heater.

An object of the present invention is to provide a particulate trap that meets this demand.

[0011]

In order to solve the above problems, in the present invention, a structure in which a sheet-like regeneration heater is faced with a predetermined interval on the exhaust gas inflow surface of a filter made of a heat resistant material. In the diesel engine particulate trap, the output of the regeneration heater is set to 400 W or less, and the heater and the filter have a filter heating amount of 0.60 W / unit area by the heater.
The structure was adopted in which the length was shortened to a value of cm ² or more, and the decrease in the surface area of the filter due to it was compensated by the increase in the filter thickness.

The filter material is preferably any one of a three-dimensional reticulated metal porous body, a ceramic fiber, a metal nonwoven fabric, or a combination thereof, because it has excellent heat resistance and a small pressure loss.

Further, the filter has a single cylindrical filter having one end of a hole as a dead end, or a cylindrical filter having a different diameter is concentrically arranged so that a space generated inside and outside the cylinder is alternately dead end at one end side and the other end side. It is preferable to use the above-mentioned multi-cylindrical filter or a parallel plate filter in which flat plate filters are arranged in parallel so that one end side and the other end side of the space between the flat plates are alternately dead ends because a large surface area (filtration area) can be secured.

Further, when the filter is formed of a laminated material of a material having a coarser material toward the exhaust gas inflow side, even if the filter thickness is increased, the particulates are collected evenly in the entire area in the thickness direction, resulting in a difference due to clogging. Pressure life is less likely to decrease.

In addition, in the particulate trap of the present invention in which the heater output is regulated to 400 W or less, the total length of the filter is 220 in order to achieve various performances in a balanced manner.
It is desirable that the filter thickness is 4 mm or less and the filter thickness is 4 mm or more.

[0016]

The shortening of the total length of the heater and the filter has the effect of raising the heating temperature with the same electric power when viewed from the heater side. As a result, the temperature difference between the filter and the heater can be made large, and as a result, the efficiency of heat transfer from the heater to the filter is improved. In particular, the radiant heat transfer amount increases in proportion to the fourth power of the temperature, so that the effect is great.

Also, shortening the total length of the filter is
It also reduces the heat dissipation surface of the heat that moves to the filter and escapes to the outside, and also suppresses heat loss.

On the other hand, when the filter length is shortened, the filter surface area is reduced accordingly, and the filter is clogged earlier to shorten the differential pressure life. However, in the present invention, the increase in the filter thickness compensates for the decrease in the surface area. The differential pressure life is not significantly reduced. Particularly, the filter in which the roughness of the filter is changed in the thickness direction of the filter so that the particulates can be collected evenly in the entire thickness direction has a great effect on this point.

According to the present invention, due to the above-described effect of improving the heat transfer efficiency and reducing the heat loss, a high differential pressure recovery rate can be obtained even though the filter thickness is increased.

[0020]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows an experimental apparatus. This device is
00cc consists of a 4-cylinder direct injection diesel engine vehicle, chassis dynamometer and dilution tunnel.

FIG. 2 shows a specific example of the particulate trap for a diesel engine of the present invention. In this particulate trap, cylindrical filters 1 and 2 having different diameters are concentrically combined, and an electric heater 3 is arranged between them.
The heater-equipped filter element 10 is mounted in the container 11 shown in FIG. FIG. 3 is a sectional view of the filter element 10 with a heater shown in FIG. The exhaust gas is introduced between the filters 1 and 2, passes through each filter, and flows to the outside of the filter 1 and the inside of the filter 2. In order to create this gas flow, the end surface on the side opposite to the gas inflow side is sealed with an iron plate 4 with a gasket interposed.

(Experimental Example 1) As the filter element shown in FIGS. 2 and 3, a cylindrical body of Ni-Cr made of Ni-based three-dimensional network structure porous body (trade name: Celmet) manufactured by Sumitomo Electric Industries, Ltd. is used. I was there. The heater 3 was formed by punching out an Inconel thin plate, adjusting the resistance, and processing it into a tubular shape, which was directly energized to generate heat.

In addition, the resistance adjustment here is such that the heater power becomes 400 W when 12 V is applied regardless of the heater length. The heater 3 may be a punching metal, an expanded metal, a metal net, or a porous metal tube used as a heat medium and a heat heater wound around the heat medium.

In this way, the filter elements with heaters of Comparative Examples 1 to 3 and Examples 1 to 3 having the specifications shown in Table 1 (see also FIG. 6) were produced.

Next, the reproduction performance of each of these samples was examined.

In the experiment, the heater-equipped filter element 10 having the shape shown in FIG. 2 was set in the container 11 shown in FIG.
Under the operating conditions of 1800 rpm and 1/4 load, particulate matter was collected in the filter element until the accumulated amount became 1.5 g.

Then, the exhaust gas under the idling operation condition (oxygen concentration 18%, temperature 100 ° C., normal flow rate 2
0V / min) 12V from low voltage power supply in atmosphere
The voltage was applied to the heater for 10 minutes to perform filter regeneration by particulate combustion, and for each filter element, the differential pressure recovery rate defined by the following equation was determined and the regeneration performance was compared. Differential pressure recovery rate = {1-A / B} × 100 (%) A = (filter differential pressure after regeneration)-(filter differential pressure before collection) B = (filter differential pressure after collection)-( Filter differential pressure before collection) The results are also shown in Table 1.

[0029]

[Table 1]

As can be seen from the above, each of the products of the present invention has a differential pressure recovery rate of more than 80% and can be sufficiently used as a particulate trap for medium and small vehicles.

(Experimental Example 2) A single filter element 20 with a heater shown in FIG. 4 (Examples 7 and 8) made of the filter material shown in Table 2 and a flat plate filter 5 as shown in FIG. A parallel plate filter element with a heater 20 (Embodiment 9) having a structure in which one end and the other end of the gap between the flat plate filters are alternately arranged to be dead ends and both ends of the gap are closed with the container 10 described above, A double-walled tubular filter element with a heater 30 (Example 10) shown in FIGS. 2 and 3 was produced.

In each of these, the resistance of the heater 3 made of an Inconel thin plate was adjusted so that the heater power shown in Table 2 was obtained when 12 V was applied. The sizes of the filter and the heater were adjusted so that the heating amount per unit area of the filter was the value shown in Table 2.

An experiment similar to that of Experimental Example 1 was conducted using this sample. As a result, the differential pressure recovery rate was obtained as shown in Table 2, and it was proved that excellent results were obtained even when the filter material was a single cylinder or a parallel plate type.

[0034]

[Table 2]

[0035]

As described above, the particulate trap of the present invention shortens the length of the heater and the filter to improve the heat transfer efficiency and at the same time reduces the heat loss, and further reduces the filter surface area by shortening the filter length. Since the structure is made up to compensate for the decrease in the filter thickness by increasing the filter thickness, it is possible to obtain a high differential pressure recovery rate with a heater power of 400 W or less without significantly lowering the collection performance. Therefore, it becomes possible to adopt a particulate trap even for a small diesel engine vehicle while the capacity of electric components is small, which is useful for environmental purification.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an experimental device used for evaluation of reproduction performance.

FIG. 2 is a perspective view showing a main element (heater-equipped filter element) of the particulate trap of the present invention.

FIG. 3 is a cross-sectional view of the filter element with a heater of the above.

FIG. 4 is a perspective view showing another example of a filter element with a heater used in the trap of the present invention.

FIG. 5 is a perspective view showing another example of a filter element with a heater used in the trap of the present invention.

FIG. 6 is a diagram showing dimensions of a filter element used in an experiment.

[Explanation of symbols]

 1, 2 Cylindrical filter 3, 13 Heater 4 Iron plate 5 Flat plate filter 10, 20, 30 Heater-equipped filter element 11 Container

Claims (5)

[Claims] 1. In a particulate trap for a diesel engine having a structure in which a sheet-like regeneration heater faces an exhaust gas inflow surface of a filter made of a heat-resistant material at a predetermined interval, the output of the regeneration heater is 400W
Furthermore, the heater and the filter are shortened to a point where the heating amount of the filter per unit area by the heater is 0.60 W / cm ² or more, and the reduction of the surface area of the filter by the increase of the filter thickness A particulate trap for diesel engines, which has been supplemented. 2. The particulate trap for a diesel engine according to claim 1, wherein the filter is made of any one of a three-dimensional reticulated metal porous body, a ceramic fiber, a metal nonwoven fabric, or a combination thereof. 3. As the filter, a single cylindrical filter in which one end of a hole is a dead end or a cylindrical filter having a different diameter is concentrically arranged so that spaces generated inside and outside the cylinder are alternately arranged on one end side and the other end side. 3. A dead-end multi-cylindrical filter, or a parallel plate filter in which plate filters are arranged in parallel and one end side and the other end side of the space between the flat plates are alternately made dead ends. Particulate trap for diesel engines. 4. The particulate trap for a diesel engine according to claim 1, 2 or 3, wherein the filter is formed of a laminated material made of a material having a coarser material toward the exhaust gas inflow side. 5. The total length of the filter is 220 mm or less,
The particulate trap for a diesel engine according to claim 1, wherein the filter has a thickness of 4 mm or more.