JPH06207560A - Exhaust gas recirculation system for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce a discharge amount of NOX, soot, and hydrocarbon by providing a gas separating part having a gas separating film located in an EGR pipe and an exhaust gas reflux means interposed in the EGR pipe. CONSTITUTION:An EGR pipe 5 is coupled to the intake air pipe 3 and the exhaust gas pipe 4 of an internal combustion engine 1 and a part of exhaust gas from the internal combustion engine 1 is returned to the intake air pipe 3. A gas separating part 2 having a gas separating film is located in the EGR pipe 5. A vacuum pump 7 serving as an exhaust gas reflux means is located downstream from the gas separating part 2. A part of exhaust gas from the internal combustion engine is fed to the separating part 2 having a carbon dioxide enriching film. After steam, carbon dioxide, and oxygen are enriched in the separating part, they are returned in intake air gas of the engine 1 with the aid of a vacuum pump 7. This constitution causes reduction of a discharge amount of NOX, soot, and hydrocarbon and prevention of the damage of the internal combustion engine and deterioration of lubricating oil owing to soot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation system for purifying exhaust gas of an internal combustion engine.

[0002]

At present, nitrogen oxide exhausted from vehicles and stationary internal combustion engine (hereinafter, referred to as NO _X), soot, hydrocarbons and the like has become a problem as an environmental pollutant. NO
_As a method of reducing _X , a method of recirculating exhaust gas to intake air of an internal combustion engine (hereinafter, referred to as EGR) is already known.

[0003]

The EGR method increases the recirculation amount of exhaust gas in order to reduce NO _X , but if the recirculation amount is increased, the emission of soot and hydrocarbons increases, The internal combustion engine is damaged by soot and dust, which accelerates the deterioration of the lubricating oil. In order to prevent this, there is a method of installing a filter in the circulation line so as not to damage the internal combustion engine, but this method cannot completely prevent wear of the internal combustion engine and deterioration of lubricating oil. If the EGR amount is increased, the oxygen concentration of the intake gas is correspondingly decreased, and the exhaust dust and the amount of hydrocarbons are increased. Therefore, reducing the NO _X alone does not completely solve the environmental problem.

An object of the present invention is to reduce the emission of NO _x , soot and hydrocarbons, and prevent damage to the internal combustion engine due to soot and the like and deterioration of lubricating oil.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that the object of the present invention can be achieved by providing a specific gas separation membrane in an EGR tube. This is what has been known, and the present invention has been completed.

That is, according to the present invention, an EGR pipe which is connected to an intake pipe and an exhaust pipe of an internal combustion engine and constitutes a flow path for returning a part of exhaust gas of the internal combustion engine to the intake pipe, and the EGR pipe is interposed. An exhaust gas recirculation device for an internal combustion engine having at least a gas separation unit having a gas separation membrane and an exhaust gas recirculation means interposed in the EGR pipe, wherein the gas separation membrane is enriched with carbon dioxide gas. Membrane, hydrogen enriched membrane, or oxygen enriched membrane.

[0007]

In the present invention, the increase in the amount of soot and hydrocarbons in the exhaust gas is mainly due to the decrease in the oxygen concentration in the intake gas. Therefore, using a gas separation membrane, water vapor in the exhaust gas By recirculating the enriched gas such as carbon dioxide and oxygen, the decrease of the oxygen concentration is minimized, the exhaustion of soot and hydrocarbons is prevented by the complete combustion of the fuel, and the heat generated by the combustion is enriched by the gas. It absorbs carbon dioxide gas and water vapor having a large specific heat to lower the temperature of the combustion chamber to reduce NO _x .

The present invention will be described in detail below.

As described above, the present invention comprises the gas separation section and the exhaust gas recirculation means provided in the EGR pipe.

The gas separation section has a gas separation membrane inside, and a known gas separator used for enriching or separating a predetermined gas can be used.

The gas separation membrane used in the present invention is not particularly limited as long as carbon dioxide and water vapor are preferentially permeated and carbon dioxide, water vapor and oxygen are selectively permeated over nitrogen gas. Non-porous polymer membranes made of materials such as silicone rubber type (polydimethylsiloxane etc.), poly (4-methyl-1-pentene), polysulfone type, cellulose acetate or ethyl cellulose type, polyamide type and the like can be used. Specific examples thereof include a carbon dioxide gas-enriched film, a hydrogen-enriched film, and an oxygen-enriched film.

The gas separation membrane may have any shape such as a flat membrane type, a spiral type and a tubular type. These films may be used alone or in plural.

The EGR amount in the present invention is 5 to 20 vol.
% Is preferable, and a range of 7 to 15 vol% is particularly preferable. The EGR amount is a ratio (vol%) of the EGR amount to the intake gas amount.

If the EGR amount exceeds 20 vol%, soot and dust increase, and if the EGR amount is less than 5 vol%, nitrogen oxides (NO _x ) increase, which is not preferable.

As the exhaust gas recirculation means, various kinds of pumps usually used for moving gas can be appropriately used, and examples of such a pump include a vacuum pump and a compressor.

The EGR pipe is connected to the intake pipe and the exhaust pipe of the internal combustion engine and constitutes a flow path for returning a part of the exhaust gas to the intake pipe, and is usually made of a metal pipe.

Further, the internal combustion engine embodying the present invention is not particularly limited, and may be a mobile type or a fixed type. These include, for example, automobile engines.

An embodiment of the present invention will be described below with reference to the drawings (flow sheet).

FIG. 1 is a flow sheet of an exhaust gas recirculation system for an internal combustion engine by a pressure reducing method. 1 is an engine, 2
Is a separation part having a gas separation membrane, 3 is an intake pipe, 4 is an exhaust pipe, 5 is an EGR pipe, and 6 is a non-permeation gas outlet pipe of gas that does not permeate the gas separation membrane. Is provided with an EGR pipe 5 that recirculates exhaust gas. This E
The gas separation unit 2 is interposed in the GR pipe 5.

A vacuum pump 7 as an exhaust gas recirculation means is provided on the downstream side of the gas separation section 2 interposed in the EGR pipe 5. The exhaust gas rich in carbon dioxide gas, water vapor, oxygen and the like which has passed through the gas separation membrane is circulated to the intake pipe 3 by the vacuum pump 7. The gas that cannot pass through the gas separation membrane 2 is returned to the exhaust pipe 4 through the non-permeable gas outlet pipe 6. The EGR pipe 5 can be provided with a control valve (not shown) for controlling the EGR amount. Further, a filter (not shown) may be provided on the EGR pipe 5 on the upstream side of the gas separation membrane 2 to remove soot and the like.

FIG. 2 is a flow sheet of an exhaust gas recirculation system for an internal combustion engine by a pressurization method. 11 is an engine,
12 is a separation part provided with a gas separation membrane, 13 is an intake pipe, 14
Is an exhaust pipe, 15 is an EGR pipe, 16 is a non-permeate gas outlet pipe of gas that does not permeate the gas separation membrane, and an EGR pipe 15 for recirculating exhaust gas is provided from the exhaust pipe 14 to the intake pipe 13. The gas separation unit 12 is interposed in the EGR pipe 15.

A compressor 17 as exhaust gas recirculation means is provided on the upstream side of the gas separation section 12 interposed in the EGR pipe 15. The exhaust gas rich in carbon dioxide gas, water vapor, oxygen, hydrogen, etc., which has passed through the gas separation membrane by the compressor 17 is recirculated to the intake pipe 13. Gas that could not permeate the gas separation membrane 12 is a non-permeate gas outlet pipe
It is returned to the exhaust pipe 14 through 6. E for the EGR pipe 15
Control valve (not shown) to control GR amount
Can be provided. Further, a filter (not shown) may be provided on the EGR pipe 15 on the upstream side of the gas separation membrane 12 to remove soot and dust.

The present invention can be constituted by either a pressure reducing method or a pressure increasing method.

[0024]

【Example】

Example 1 With the EGR amount kept constant by the depressurization method, NO _X and dust were measured for the case without a gas separation membrane (prior art, comparative example) and the case with a gas separation membrane (present invention, example).

The engine used was made by Komatsu Ltd.
It was EG85CDBS # 1005.

As the gas separation membrane, a hydrogen enriched membrane manufactured by Matsushita Electric Industrial Co., Ltd. was used. The inlet temperature of the separation membrane was 130 ° C and the outlet temperature was 100 ° C.

The results are shown in Table 1.

[0028]

[Table 1] From Table 1, when the EGR amount constant, the present invention is the generation amount of the NO _X and dust as compared with the prior art is small, it can be seen that the effect of gas separation membranes. A property test (viscosity, insoluble matter, total base number) of the lubricating oil used in the engine was conducted. The results are shown in FIGS. 3, 4 and 5. Figure 3,
From FIG. 4 and FIG. 5, the present invention has less change in the properties (viscosity, insoluble matter, total base number) of the lubricating oil as compared with the prior art,
It can be seen that there is little deterioration of the lubricating oil. Further, when an engine endurance test was conducted, the present invention showed almost no engine wear even after 2000 hours, but the prior art showed considerable engine wear. Table 2 shows the composition of the exhaust gas used in the experiment and the composition of the gas that has permeated the gas separation membrane.

[0029]

[Table 2] Example 2 Using the apparatus of Example 1, the NO _X amount was made constant by a decompression method, and the EGR amount was compared with the case without a gas separation membrane (Comparative Example 2) and the case with a gas separation membrane (Example 2). The amount of soot and dust was measured. The results are shown in Table 3. From Table 3, N
It can be seen that when the amount of O _X is constant, the amount of EGR is small and the amount of dust generated is small. Thus, when the gas separation membrane is used, the EGR amount can be reduced. Table 2 shows the composition of the exhaust gas used in the experiment and the composition of the gas that permeated the gas separation membrane.
It was almost the same as that shown in.

[0030]

[Table 3]

[0031]

According to the present invention, NO _X and soot in the exhaust gas can be reduced, the EGR amount can be reduced, and further damage to the internal combustion engine and deterioration of the lubricating oil of the engine can be prevented.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

FIG. 2 is a flow sheet showing another embodiment of the present invention.

FIG. 3 is a graph showing a change in viscosity of lubricating oil used in an engine.

FIG. 4 is a graph showing changes in insoluble matter of lubricating oil used in an engine.

FIG. 5 is a graph showing changes in the total base number of the lubricating oil used in the engine.

[Explanation of symbols]

 1 Engine 2 Separation Part 3 Intake Pipe 4 Exhaust Pipe 5 EGR Pipe 6 Outlet Pipe 7 Vacuum Pump 11 Engine 12 Separation Part 13 Intake Pipe 14 Exhaust Pipe 15 EGR Pipe 16 Outlet Pipe 17 Compressor

Claims (2)

[Claims] 1. An EGR pipe which is connected to an intake pipe and an exhaust pipe of an internal combustion engine and constitutes a flow path for returning a part of exhaust gas of the internal combustion engine to the intake pipe, and a gas separation membrane interposed in the EGR pipe. An exhaust gas recirculation apparatus for an internal combustion engine, comprising: at least a gas separation unit including: and an exhaust gas recirculation unit interposed in the EGR pipe. 2. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, wherein the gas separation membrane is a carbon dioxide gas enriched membrane, a hydrogen enriched membrane, or an oxygen enriched membrane.