JPS58187572A - Exhaust gas recirculating device for diesel engine - Google Patents

Abstract

PURPOSE:To filtrate carbon particles in the exhaust gas nicely for a long period of time by a method wherein a plurality of filtrating units, consisting of a main exhaust gas flowing pipeline, equipped with frustoconical inner walls whose diameters are reduced lengthwisely, and an annular filtrating member, fitted to the outer periphery of the pipeline, are connected in series. CONSTITUTION:In case a part of the exhaust gas, discharged through an exhaust gas collecting pipe 4, is recirculated into a suction system through a filtrated exhaust gas outlet port 8 connected to a suction pipe, a part of the carbon particles in the exhaust gas collide against the frustoconical inner walls provided in the main exhaust gas flowing pipelines 1a-1c and advance along the surfaces of the walls without changine the advancing directions thereof. On the other hand, the flow of the exhaust gas is changed to the flow along the radial directions of the pipelines at the outlets of the opening ends which are the small diametral sides (outlet sides) of each pipelines 1a-1c. In this case, the exhaust gas moves toward the recesses 21 of the filtrating members 2a-2c under accompanying said carbon particles. Next, when the exhaust gas is passing through the filtrating members 2a-2c, the carbon particles are filtrated and are oxidized by a high-temperature circumstance thereby being eliminated as carbon diexide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation device for reducing the concentration of nitrogen oxides and the amount of carbon particles in the exhaust gas of a diesel engine.

Diesel engines generate an output corresponding to the fuel consumption by spraying the fuel such as light oil into a mist into the combustion chamber, mixing it with air and burning it. Attempting to obtain high output with as small an air excess ratio as possible increases the temperature and pressure within the combustion chamber, which tends to increase the concentration of nitrogen oxides in the exhaust gas. As is well known, nitrogen oxides are one of the substances that cause air pollution, and emissions from automobiles and boilers are strictly regulated, but even in diesel engines, the concentration of nitrogen oxides in the exhaust must be kept as low as possible. Needless to say, it is desirable to do so.

In order to solve the problems of low fuel consumption and low nitrogen oxide concentration, we have improved the structure of the combustion chamber, improved the function of the fuel injection system, especially the fuel injection valve, and adjusted and controlled the fuel injection timing and injection amount. Many attempts have already been made, including the use of additives such as barium carbonate in light oil, but none have yielded satisfactory results.

In addition to the above-mentioned methods for controlling the combustion phenomena and combustion processes inherent in diesel engines, the exhaust gas recirculation method (so-called EGR method), which is implemented in gasoline engines to reduce the concentration of nitrogen oxides in the exhaust gas, is used in diesel engines. Of course, it is also conceivable that the system could be adopted by institutions. However, unlike that of a gasoline engine, the exhaust from a diesel engine contains a large amount of carbon particles produced by incomplete combustion of the fuel, and if this exhaust is mixed with the intake air and introduced into the cylinder, the intake valve Carbon particles adhere to and accumulate on the seats and valve stems, which not only causes damage to the intake valve and deteriorates its function, but also causes accidents, so it is easier to use EGR for diesel engines than for gasoline engines. I can't do that.)

An object of the present invention is to provide a means for purifying the exhaust gas of a diesel engine.
The object of the present invention is to separate carbon particles in the exhaust gas of a diesel engine, which are an obstacle to implementing the R method, by a simple means, and to enable exhaust gas recirculation using only clean exhaust gas.

The present invention, which has succeeded in achieving the object set forth in item L, provides an exhaust gas recirculation device for adopting the EGR method in a diesel engine. First, to give an overview, the exhaust gas recirculation device of the present invention (a) An exhaust main flow pipe having a conical inner wall whose inner diameter decreases in the length direction; and (b) An exhaust flow pipe consisting of a heat-resistant filter material capable of filtering out carbon particles in the exhaust gas. It is an annular pipe having an inner diameter larger than the outer diameter of the pipe and has four parts on the inside, and is arranged so that the four parts are on the radial extension of the open end of the main exhaust flow pipe with the smaller inner diameter. A filtration member integrated with the main flow pipe; a partial exhaust filtration unit consisting of a filtration unit, or a partial exhaust filtration unit formed by connecting a plurality of these in series; A filtered exhaust gas collecting chamber equipped with a means for connecting the diesel engine to the exhaust gas collecting pipe of the diesel engine is installed at the part where the open end of the main exhaust flow pipe with a larger inner diameter appears, and a means for connecting to the exhaust main flow pipe of the diesel engine is installed in the part where the open end of the main exhaust flow pipe has a smaller inner diameter. The portion where the opening end appears is provided with connection means for connecting to an exhaust pipe.

The present invention will be described below with reference to one page for each specific example.

FIG. 1 is a partially cutaway side view showing an example of the exhaust gas recirculation device of the present invention, and FIG. 2 is a sectional view taken along line XX in FIG. 1.

In both figures, 1 is the main exhaust flow pipe made of stainless steel (ceramics may also be used), and as is clear from Fig. 3, which shows this pipe alone, the pipe wall is shaped like the side of a truncated cone. It is of shape. The inner diameter at the open end 11 with the smaller inner diameter is substantially equal to the inner diameter of the exhaust manifold of the diesel engine to which this exhaust gas recirculation device is installed. The angle θ of the inclination of the tube wall with respect to the central axis is
Preferably it is 25 to 30 degrees.

Reference numeral 2 denotes a filter member, which is a heat-resistant member made of porous porcelain that can filter out carbon particles in the exhaust gas. Its shape is
As shown in FIG. 2, it is annular as a whole, but as shown in FIG. 1, it has a C-shaped cross section and has a recess 21 on the inside of the ring. Exhaust main flow pipe 1
and the filtering member 2 are combined in the illustrated arrangement to form a partial exhaust filtration unit, and in the illustrated example, three of these units are connected in series in a coaxial arrangement, and a cylindrical filter is formed. It is housed in case 3. The case 3 has an exhaust port 31 and an exhaust outlet 32 at one end of the center of the exhaust gas partial filtration unit, and the ends of these openings are shaped like 7 runches, and are connected to the exhaust manifold pipe 4 and the exhaust of the diesel engine. Connected to pipe 5. The case 3 also has a partially raised body to form a filtered exhaust gas collection chamber 6.
This bulge is provided with an outlet 8 for the filtered exhaust gas (
Outlet 8 is connected to the intake pipe of the tea cell engine). As shown in FIG. 2, the filter member 2 has irregularities that repeat in the circumferential direction on the outside, and is in contact with the case 3 at the convex portion 22. Therefore, there is a gap G between the recess 23 and the case 3, and the gap G extends into the filtered exhaust gas collection chamber 6.

FIG. 1 is an explanatory view of the exhaust gas recirculation device connected to the intake and exhaust system of the diesel engine 10, and 9 is an intake pipe.

Further, arrows P and Q represent the flow of exhaust gas and suction λ of the tea cell engine, respectively, and arrow R represents the flow of exhaust gas filtered by the exhaust gas recirculation device.

Figure 5 is an explanatory diagram of the principle that when the above-mentioned exhaust gas recirculation device is used, the exhaust gas is partially filtered and clarified, and at the same time, the concentration of carbon particles in the exhaust gas discharged into the fire is reduced. be. A part of the carbon particles (indicated by black dots) in the exhaust gas entering from the exhaust port 31 collide with the tapered conical inner wall of the exhaust main flow pipe and proceed along the wall surface. On the other hand, as shown by the streamlines in this country, the flow of exhaust gas travels almost straight through the main exhaust flow pipe 1a, and then exits through the open end 11a of the main exhaust flow pipe 1a, whichever is smaller in inner diameter. At this point, a flow is generated in the radial direction of the open end.

Of course, this radial flow mainly originates from near the pipe wall of the exhaust main flow pipe 1a, so most of the carbon particles that have proceeded along the pipe wall change their direction of movement in the radial direction of the pipe. . The radially directed exhaust air and carbon particles reach the four parts 21 of the filter element 2a. Based on the above structure, the pressure in the fourth part 21 is equal to the pressure in the exhaust system, which is considerably higher than atmospheric pressure, and the pressure in the gap G is approximately equal to the pressure in the intake system, which is lower than atmospheric pressure. Due to this differential pressure, the exhausted exhaust gas passes through the micro gap of the filter member 2a and reaches the gap G, and is then connected to the filtered exhaust gas collecting chamber 6 and the outlet 8.
It enters the intake pipe 9 via the . At that time, the carbon particles are separated by the filtration action of the filtration member 2a, and most of the carbon particles are
a (some carbon particles are deposited in the deep pocket-like portion 24 of the fourth part 21). Exhaust main flow pipe 1a
The exhaust gas that has gone straight without changing direction after leaving the exhaust gas enters the next filtration unit consisting of the main exhaust flow pipe 1b and the filtration member 2b, where it is subjected to the same filtration action as described above. The same filtration action is repeated in the next filtration unit, and as a result, the filtered exhaust gas collection chamber 6 is provided with the amount of clean exhaust gas necessary to suppress the generation of nitrogen oxides by the EGR method. , the carbon particle concentration of the exhaust gas discharged into the atmosphere via the exhaust outlet 32 and the exhaust pipe 5 is higher than that of the carbon particles left on the filter member 2 than when this exhaust gas recirculation device was not used. If the temperature of the exhaust gas treated by this device is about 500°C or higher, it will gradually be oxidized by the oxygen in the air and become carbon dioxide gas, which will enter the filtered exhaust gas. Therefore, even if it is used for a considerable period of time, the filter member 2 will not become clogged, and if it does, it is sufficient to disassemble it and bake only the filter member 2 in an oxidizing atmosphere.

In order to ensure smooth automatic purification of the filter member 2 by the above mechanism, the exhaust gas recirculation device of the present invention is connected to the exhaust manifold pipe as close as possible to the diesel engine body, so that the exhaust gas as high as possible can be treated. This is desirable.

EG of diesel engine using exhaust gas recirculation device of the present invention
When carrying out the R method, in order to set the recirculation amount of filtered exhaust gas at a desired ratio to the intake air amount, for example, the filtered exhaust gas collection chamber 6 and the intake pipe 9 are connected as shown in FIG. A valve 13 is provided in the intake pipe, and the opening degree of this valve is controlled based on pressure fluctuations in the intake pipe, which correspond to fluctuations in the intake amount when the engine speed fluctuates, or in the case of automobile diesel engines. may be adjusted in accordance with the amount of depression of the accelerator.

The exhaust gas recirculation device of the present invention is based on the above-described structure, and the exhaust gas recirculation device reduces the amount of exhaust gas generated by the exhaust gas from which carbon particles have been removed to a substantially harmless extent.
This makes it possible to implement the GR method, and its unique mechanism that utilizes the fluid characteristics of the exhaust and the pressure difference between the exhaust system and the intake system does not create excess back pressure in the diesel engine's exhaust system. . Therefore, by using this, the amount of nitrogen oxides and carbon particles in the exhaust gas can be reduced without detracting from the essential performance of the diesel engine. Furthermore, as mentioned above, the exhaust gas recirculation device of the present invention maintains its function over a long period of time without clogging, and the overall structure is strong, so it requires little maintenance during use. No inspection required. Therefore, it is particularly suitable for use in an engine, such as a diesel engine of an automobile, in which constant maintenance and inspection is difficult and the operating conditions are severe.

[Brief explanation of drawings]

Part 1l: Partially cutaway side view of the exhaust gas recirculation device according to the invention. FIG. 2: A sectional view taken along line XX in FIG. 1. FIG. 3: A perspective view of the exhaust main flow pipe 1. FIG. 4: An explanatory diagram of the exhaust gas recirculation device shown in FIG. 1 installed in a diesel engine. FIG. 5: An explanatory diagram of the operation of the exhaust gas recirculation device shown in FIG. 1. 1: Exhaust main flow pipe 2: Filter member 3: Case 4: Exhaust collecting pipe 5: Exhaust pipe
6: Filtered exhaust gas collection chamber 8: Filtered exhaust outlet
9: Intake pipe 10: Diesel engine agent Patent attorney Itai - Taki Figure 1 Figure 2 Figure 3 Decoy

Claims (1)

[Scope of Claims] An exhaust main flow pipe having a conical inner wall whose inner diameter decreases in the length direction; and a heat-resistant filter material capable of filtering out carbon particles in the exhaust; It is an annular structure having an inner diameter larger than the outer diameter and with four parts facing south inward, and is arranged such that the concave portion L is located on the radial extension of the open end of the main exhaust flow pipe with the smaller inner diameter. The filter member is integrated with the main exhaust flow pipe. A filtered exhaust collecting chamber equipped with a means for connecting to the intake pipe of the diesel engine is connected to the opening 1] end of the main exhaust flow pipe with a larger inner diameter, and a means for connecting to the exhaust pipe of the diesel engine is connected to the exhaust pipe. An exhaust gas recirculation device in which a connecting means with an exhaust pipe is provided at the portion where the open end of the main flow pipe, whichever has the smaller inner diameter, appears.