JPH109090A - Fuel injection nozzle for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fuel consumption from being degraded in the combustion of thinned and premixed diesel oil, and simultaneously reduce smoke and NOx to a great extent. SOLUTION: This invention is concerned with the fuel injection nozzle to be used for the combustion of thinned and premixed diesel oil where fuel is injected right after a suction stroke has been started, and also in the range of a compression strole. The nozzle is equipped with a fuel passage 12, a nozzle body 10 including a seat part 13 formed in such a way that its diameter is gradually made small, and an injection port 14 formed at its tip end, a valve main body 15, an inclined part 16 provided for the lower portion of the valve main body 15, and with a needle valve 11 including a guide part 17 formed in a recessed surface shape at the lower portion of the inclined part 16. In this case, the inclined part of the needle valve 11 can be brought into contact with the seat part of the nozzle body 10, and the guide part 17 is disposed in such a way as to be projected out of the injection port 14 toward the outside part of the nozzle body 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a fuel injection nozzle of a diesel engine, belonging to the technical field of order to simultaneously and significantly reduce the NO _X and smoke.

[0002]

2. Description of the Related Art In a direct injection type diesel engine, a method of devising a nozzle injection hole shape based on high-pressure fuel injection or a method of mounting a plurality of injectors and independently controlling the injection timing and injection amount of each of them has been proposed. Attempts have been made to reduce _X and smoke. However, in any of the methods, the concentration distribution of the fuel inside the spray is very uneven, and the ignition delay time from when the fuel is injected to when it starts burning is short, so that the mixing of the fuel and the air does not proceed. It starts burning in a state, the high concentration part of the fuel burns and smoke is generated, and the lean part burns in a lean state with a lot of air, but the fuel and air are in the middle of the high concentration part and the lean part. there are regions of stoichiometric burning in equal amounts, wherein the high concentration of the NO _X are produced.

In order to solve this problem, fuel is injected into the cylinder at a considerably earlier time than in the prior art, and a sufficient premixing time is given to form a lean premixed gas, which is compressed and self-ignited. Premixed Lean Diesel Combustion (PREDIC), which can reduce _X and smoke simultaneously and significantly, has been proposed. Vol. III, September 11-13, 1995, pp. 188-189). This will be described with reference to FIGS. In FIG. 2, reference numeral 1 denotes a piston, 2 denotes a cylinder, 3 denotes a cylinder head, and 4 denotes a cavity. Two side injectors 9A and 9B are disposed on the outer peripheral side of the combustion chamber 6 so as to face diagonally downward. ing.

FIG. 3 shows an example of test results of a conventional example and PREDIC, and shows the engine performance (fuel efficiency ISFC g / kWh) and the characteristics of various emissions at an engine speed of 1000 rpm. In the figure, ● shows a conventional example in which the excess air ratio λ = 2.7, and □, Δ, △, and Δ indicate the excess air ratio λ = 2.5, 2.7, 3 in PREDIC. ., 3.7 are shown.

[0005] In the case of the conventional example, when delayed fuel injection timing near the top dead center, there is a limit but NO _X concentration is lowered,
It increases with further delay. On the other hand, in PREDIC,
For example, when fuel is injected at about 80 ° before the top dead center under the operating condition of λ = 2.7, the engine can be operated by compression self-ignition of the lean premix, and the NO _X concentration at this time is about 20 ppm. This can be greatly reduced to 1/10 or less of the minimum value of the conventional example. If the fuel injection timing is earlier than this, the fuel becomes too dispersed and becomes thin and difficult to ignite, causing misfire. Therefore, normal operation cannot be performed. If the fuel injection timing is delayed (θ = −64 ゜ ATDC), the NO _X concentration becomes When the angle is retarded so far, knocking becomes severe and the injection timing cannot be further delayed. Even if the fuel injection amount is reduced (λ = 3.
1, 3.7), the NO _X concentration shows a similar tendency, and a drastic reduction is possible. When the injection amount is increased (λ = 2.
5), can not be operated only within a narrow range injection timing of a misfire and knocking approaches, NO _X concentration becomes possible similarly significant reduction.

[0006] When the thus drastically reduce NO _X concentration is obtained, smoke in PREDIC (BSU) is almost equal to the level of the prior art, also the fuel consumption rate (ISF
C.) is almost the same, or only an increase of about 15% at the maximum. On the other hand, the total hydrocarbon (THC) and CO concentrations are greatly increased to about 2000 to 5000 ppm, but this level is equivalent to that of a gasoline engine, and there is no problem if reduced with a normal oxidation catalyst.

[0007] From the test results of FIG. 3, with respect to the excess air ratio lambda, it is possible to set the fuel injection timing can be significantly reduced NO _X, at least, the excess air ratio lambda>
2.5, by setting the fuel injection timing θinj in the range of crank angle -125 ° to-20 ° ATDC, it is possible to simultaneously and significantly reduce the NO _X and smoke.

[0008]

In the above-mentioned conventional lean premixed diesel combustion, fuel is simultaneously injected from two side injectors at an early stage and made to collide with each other to form a lean mixture in the center of the cylinder. However, in this method,
A part of the fuel passes through the collision and easily reaches the cylinder liner and the piston, and the fuel attached to the wall surface has a problem that the combustion is significantly inhibited and the fuel efficiency is deteriorated. This problem is more pronounced because the earlier the fuel injection timing, the lower the cylinder pressure. In order to solve this problem and effectively use the fuel for combustion, it is necessary to form a lean and uniform air-fuel mixture with advanced atomization, and also to make the spray penetration force relatively small.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and problems. In lean premixed diesel combustion, the fuel consumption is prevented from deteriorating by reducing the penetration force of the spray to prevent the spray from reaching the wall surface. The formation of an air-fuel mixture with advanced atomization in a short time makes it possible to produce smoke and N
It is an object of the present invention to provide a diesel engine fuel injection nozzle capable of simultaneously and significantly reducing OX.

[0010]

In order to achieve the above object, a fuel injection nozzle of a diesel engine according to the present invention is used for lean premixed diesel combustion in which fuel is injected within a compression stroke immediately after the start of an intake stroke. A fuel injection nozzle to be used, a nozzle body 10 having a fuel passage 12, a seat portion 13 having a diameter gradually reduced, and an ejection port 14 formed at a tip end, a valve body 15, and a lower portion of the valve body. A needle valve 11 having an inclined portion 16 provided and a guide portion 17 formed in a concave surface below the inclined portion, and the inclined portion of the needle valve can be brought into contact with a seat portion of the nozzle body. The guide portion is disposed so as to protrude from the nozzle to the outside of the nozzle body. Note that the numbers added to the above configuration are compared with the drawings for easy understanding of the present invention, and the present invention is not limited thereto.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a fuel injection nozzle for a diesel engine according to the present invention. FIG. 1 (A) is a plan view of a combustion chamber, FIG. 1 (B) is a sectional view of the combustion chamber, and FIG.
(C) is a sectional view of the fuel injection nozzle.

1 (A) and 1 (B), a piston 1 is slidably fitted in a cylinder 2, and a cylinder head 3 is fixed above the cylinder 2. A concave cavity 4 is formed at the top of the piston 1, and a combustion chamber 6 is formed in a space surrounded by the cylinder 2, the piston 1, and the cylinder head 3. A fuel injection nozzle 5 is disposed in the cylinder head 3 at a substantially central portion of the combustion chamber 6. In the present invention, the fuel is injected from the fuel injection nozzle 5 into the combustion chamber 6 within the range of the compression stroke immediately after the start of the intake stroke, and a uniform lean mixture is formed before reaching the top dead center where combustion is performed. However, this is compressed and self-ignited, so that NO _X and smoke are reduced simultaneously and significantly.

In FIG. 1C, the fuel injection nozzle 5
Is composed of a nozzle body 10 and a needle valve 11 slidably fitted in the nozzle body 10. The nozzle body 10 includes a fuel passage 12, a seat portion 13 having a diameter gradually reduced, and an ejection port 14 formed at a tip end.
The needle valve 11 includes a valve body 15, an inclined portion 16 provided below the valve body, and a guide portion 17 formed in a concave shape below the inclined portion 16. The inclined portion 16 of the needle valve 11 can be brought into contact with the seat portion 13, and the guide portion 17 is disposed so as to project from the ejection port 14 to the outside of the nozzle body 10.

The operation of the present invention having the above configuration will be described. When the needle valve 11 moves upward in FIG. 1C, the fuel in the fuel passage 12 is turned inward along the seat portion 13 and sent to the guide portion 17 of the needle valve 11. In the guide section 17, the fuel that has flowed in from the upstream at a high pressure receives
The spray flows along the concave surface of the nozzle 7 and is sprayed tangentially from the outlet 14 to form an umbrella-like spray. This umbrella-shaped spray has a large surface area and a small penetrating force due to an increase in shear resistance due to an increase in the contact area with air. Therefore, since the surface area of the spray is large, air introduction is promoted, and atomization and dilution are promoted. In addition, because of the high-pressure injection, the above-described effects can be maintained regardless of whether the pressure in the cylinder is high or low. In order to increase the surface area of the spray, it is necessary to reduce the thickness of the liquid film near the end portion 17a of the guide portion 17. Therefore, the surface of the guide portion 17 is roughened so that the fuel flow proceeds smoothly. A smooth state close to a small mirror surface is preferable.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made.

[0016]

As is apparent from the above description, according to the present invention, as a result of forming a jet in the nozzle along the concave guide, the spray penetrating force is relatively small, so that the spray is , The deterioration of fuel efficiency can be prevented. Further, since a lean and finely-mixed mixture can be formed in a short time, fuel injection at a piston position close to the top dead center can be realized as compared with the lean premixed diesel combustion described in the related art, At this time, since the pressure in the cylinder is high, the adhesion of fuel to the wall surface can be prevented. In lean premixed combustion on the premise of self-ignition, a shorter elapsed time from injection to combustion is advantageous in controlling combustion, and also has an advantage in this respect.

As a result, in the lean premixed diesel combustion, the fuel penetration is reduced to prevent the fuel from reaching the wall surface, thereby preventing the deterioration of the fuel efficiency and forming the lean and highly atomized mixture in a short time. Thereby, smoke and NOx can be reduced simultaneously and significantly.

[Brief description of the drawings]

FIG. 1 shows a fuel injection nozzle 1 of a diesel engine according to the present invention.
1A shows a plan view of a combustion chamber, and FIG.
FIG. 1B is a sectional view of a combustion chamber, and FIG. 1C is a sectional view of a fuel injection nozzle.

FIG. 2 shows an example of conventional lean premixed diesel combustion,
FIG. 2A is a plan view of the combustion chamber, and FIG. 2B is a cross-sectional view of the combustion chamber.

FIG. 3 is a diagram for explaining the effect of the lean premixed diesel combustion of FIG. 2;

[Explanation of symbols]

5: Fuel injection nozzle, 10: Nozzle body, 11: Needle valve 12: Fuel passage, 13: Seat part, 14: Injection port, 15
… Valve body 16… inclined part, 17… guide part

Claims (1)

[Claims] 1. A fuel injection nozzle used for lean premixed diesel combustion for injecting fuel within a range of a compression stroke immediately after the start of an intake stroke, wherein a fuel passage and a seat portion whose diameter is gradually reduced are provided. A nozzle body having a nozzle body formed at the tip, a valve body, a needle portion having a slope portion provided below the valve body, and a guide portion formed in a concave surface below the slope portion. A fuel injector for a diesel engine, characterized in that an inclined portion of a needle valve can be brought into contact with a seat portion of the nozzle body, and the guide portion is disposed so as to protrude from the nozzle to the outside of the nozzle body. nozzle.