JPH0565820A - Exhaust emission control method of diesel engine - Google Patents

Abstract

PURPOSE:To reduce soot and NOx simultaneously by increasing the amount of hydrocarbon in a combustion chamber actively and utilizing the as a reducing agent which removes NOx. CONSTITUTION:A main fuel infection valve 5 which supplies main fuel into a combustion chamber 4 of a diesel engine 1, an ultrasonic atomizer 11 which supplies auxiliary fuel into an air suction pipe 9, and a catalyst device 12 which is provided in an exhaust pipe 10 and selects and reduces nitrogen oxides under coexistence of reducing agents of oxygen and hydrocarbon are provided. The amount of hydrocarbon after combustion is increased by controlling the supplying amount of auxiliary fuel.

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to an exhaust gas purification method for a diesel engine can be achieved simultaneously reduce the soot and nitrogen oxides (NO _X).

[0002]

2. Description of the Related Art In a diesel engine, in order to efficiently convert the energy of fuel into work, a mixture of fuel and intake air is created completely and quickly, and the air in the combustion chamber completely burns the fuel. thing is required, NO _X is produced to combustion takes place at high temperature. Therefore, in order to reduce NO _X , the fuel injection timing is mainly delayed, but combustion is incomplete and soot increases, and to reduce soot, swirl, squish, etc., are used to expedite fuel and air. a method of mixing is adopted, the initial combustion of the heat generation rate increases, has a contradictory problem that causes an increase in NO _X, which makes it difficult to simultaneously reduce the soot and NO _X .. Moreover, in the diesel engine, the three-way catalyst used in the gasoline engine cannot be used because the amount of oxygen in the exhaust gas is large.

On the other hand, selects the NO _X as the technique for removing NO _X, ammonia (NH ₃₎ or zeolite-based hydrogen carbide (HC) and a reducing agent, alumina-based, in the presence of oxygen using a catalyst of the copper-based Various proposals for reduction have been made.

[0004]

However, the above N
In order to apply the technology for removing O _x to diesel engines, NH ₃ or HC must be added to the exhaust system,
When expensive and dangerous NH ₃ is added, it requires a special device for it and is not practical, and H ₃ is added to the exhaust system.
When C is added, it is possible to add propane, light oil, etc. However, the amount of C does not contribute to combustion, which causes a problem that fuel consumption is reduced. Further, in a device that supplies the exhaust gas to high temperature exhaust gas. There are also problems.

By the way, as a technique for reducing soot,
A main fuel injection valve was provided facing the combustion chamber of the diesel engine, and an ultrasonic atomizing device for supplying auxiliary fuel was provided in the intake pipe, and atomized by the action of ultrasonic vibration of this ultrasonic atomizing device. A method is known in which fuel is supplied to a combustion chamber during an intake stroke, and a low temperature oxidation reaction is caused during a compression process to improve combustion of a main fuel, thereby reducing soot in exhaust gas (for example, Japanese Patent Laid-Open Publication No. Sho. 57-102545).

However, in the above-mentioned conventional soot reduction system, as shown in FIG. 2, when the supply ratio of the auxiliary fuel to the total fuel is increased, the soot gradually decreases, while the HC in the exhaust gas is reduced. It gradually increases, for example, when the ratio of the auxiliary fuel to the total fuel supply reaches 30%,
The problem arises that the concentration increases to 1000 ppm. The reason is that incomplete combustion occurs due to cooling by the wall surface between the outer circumference of the piston and the cylinder head because a lean air-fuel mixture is sucked from the intake pipe, and fuel droplets adhere to the cylinder liner. The fuel in the intake pipe may flow into the exhaust pipe due to a slight timing difference between the intake valve and the exhaust valve. Therefore, H has never been a problem in diesel engines.
The new problem of reduction of C will arise.

The present invention solves the above problem by positively increasing the amount of hydrocarbons in the combustion chamber to reduce NO.
_An object of the present invention is to provide a method for purifying exhaust gas of a diesel engine, which is capable of simultaneously reducing soot and NO _x by utilizing it as a reducing agent for removing _X.

[0008]

To this end, the method for purifying exhaust gas of a diesel engine according to the present invention uses a main fuel injection valve 5 for supplying main fuel to a combustion chamber 4 of a diesel engine 1.
And an ultrasonic atomizing device 1 for supplying auxiliary fuel into the intake pipe 9.
1 and a catalyst device 12 arranged in the exhaust pipe 10 for selectively reducing nitrogen oxides in the coexistence of a reducing agent for oxygen and a hydrocarbon, and controlling the supply amount of the auxiliary fuel after combustion. It is characterized by increasing hydrocarbons.
It should be noted that the numbers added to the above-mentioned configurations are for comparison with the drawings for easy understanding, and the configurations of the present invention are not limited thereby.

[0009]

In the present invention, the auxiliary fuel atomized by the action of the ultrasonic vibration of the ultrasonic atomizing device 11 in the intake stroke is sucked into the combustion chamber 24, and in the compression process,
It is injected from the main fuel injection valve 25 to cause a low temperature oxidation reaction,
The atmosphere in the cylinder that is extremely easy to ignite is created, the ignition of the main fuel is assisted, and the combustion is promoted. Further, the HC increased by the combustion is used as a reducing agent in the catalyst device 12, and NO _X is selectively reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a diesel engine according to the present invention. In a diesel engine 1 according to the present invention, a combustion chamber 4 is formed by a cylinder 2 and a piston 3, and a main fuel injection valve 5, which faces the combustion chamber 4,
An intake valve 6 and an exhaust valve 7 are arranged, the intake valve 6 is connected to an intake pipe 9, and the exhaust valve 7 is connected to an exhaust pipe 10.
An ultrasonic atomizing device 11 for supplying auxiliary fuel is mounted in the intake pipe 9, and a catalyst device 12 is arranged in the exhaust pipe 10. The ultrasonic atomization device 11 is a device that ultrasonically vibrates a vibrator horn by an electric-acoustic conversion element to atomize the fuel supplied to the vibrator horn into fine droplets.

The catalyst device 12 is a zeolite-based, alumina-based, or copper-based catalyst capable of selectively reducing NO _{x in} the presence of oxygen and a hydrocarbon-based reducing agent. It is carried.

The operation of the present invention having the above-mentioned structure will be described. During the intake stroke, the auxiliary fuel atomized by the action of ultrasonic vibration of the ultrasonic atomizer 11 is sucked into the combustion chamber 24 and is compressed in the compression process. , Main fuel injection valve 25
The fuel is injected from a low temperature oxidation reaction to create an atmosphere that is extremely ignitable in the cylinder, assists ignition of the main fuel, and promotes combustion, so that the generation of soot in the exhaust gas is reduced. At this time, by controlling the supply ratio of the auxiliary fuel to the total fuel to, for example, 30%, the concentration of HC after combustion is increased to 1000 ppm, and the increased HC is reduced in the catalyst device 12, as shown in FIG. the NO _X selected reduction by utilizing as agent,
Therefore, not only HC but also smoke and NO _X can be simultaneously reduced.

[0013]

As is apparent from the above description, according to the present invention, the main fuel injection valve for supplying the main fuel to the combustion chamber of the diesel engine and the ultrasonic atomizing device for supplying the auxiliary fuel into the intake pipe are provided. A catalyst device disposed in the exhaust pipe for selectively reducing nitrogen oxides in the coexistence of oxygen and a hydrocarbon reducing agent, and controlling the supply amount of the auxiliary fuel to remove the hydrocarbons after combustion. is increased, by utilizing this increase actively hydrocarbons in the combustion chamber as a reducing agent for removing NO _X, it is possible to reduce the soot and NO _X at the same time.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a diesel engine according to the present invention.

FIG. 2 is a diagram showing a relationship between soot and HC concentrations with respect to an auxiliary fuel supply ratio in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Cylinder, 3 ... Piston, 4 ... Combustion chamber 5 ... Main fuel injection valve, 6 ... Intake valve, 7 ... Exhaust valve, 9 ... Intake pipe, 10 ... Exhaust pipe 11 ... Ultrasonic atomizer , 12 ... Catalyst device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sakuro Kokubo 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (1)

[Claims] 1. A main fuel injection valve for supplying a main fuel to a combustion chamber of a diesel engine, an ultrasonic atomizing device for supplying an auxiliary fuel into an intake pipe, and an exhaust pipe which are provided to reduce oxygen and hydrocarbons. An exhaust gas purification method for a diesel engine, comprising: a catalyst device for selectively reducing nitrogen oxides in the coexistence of an agent, wherein the hydrocarbon after combustion is increased by controlling the supply amount of the auxiliary fuel. ..