JP2564854B2 - Spark assist diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a spark assist diesel engine in which a low cetane number fuel such as methanol or alcohol is directly atomized in a combustion chamber of a piston and burned by spark assist. Regarding

[Prior Art] As an internal combustion engine for burning a low cetane number fuel such as methanol or alcohol, there is an internal combustion engine shown in FIG.

As shown in the figure, in this internal combustion engine, a fuel injection nozzle b is disposed at a substantially axial center position of a circular (horizontal cross section) combustion chamber a, with the fuel injection nozzle b facing the combustion chamber a. In b, a plurality of injection ports j to o for supplying the fuel sprays d to i are provided on the inner peripheral wall c on one side of the combustion chamber a at substantially regular intervals in the swirl direction.

[Problems to be Solved by the Invention] In the combustion mechanism of the internal combustion engine described above, first, the fuel spray upstream in the swirl direction is ignited by the discharge of the spark plug p provided immediately downstream of the spray, and the generated flame is swirled. This is achieved by successively propagating the flame to each fuel spray supplied downstream in the direction. However, focusing on the fuel spray on the most downstream side after ignition and the time difference between this fuel spray and the flame propagation, the fuel spray on the most downstream side has a time to generate an air-fuel mixture from the time of ignition to the flame propagation. On the other hand, there is a problem that the upstream side does not have a relatively long time to generate the air-fuel mixture.

That is, between the fuel sprays on the downstream side, while there are air-fuel mixtures that propagate flames with each other, as they go toward the upstream side,
This is because there is no air-fuel mixture that propagates the flame, and a rare zone (only air) exists between the sprays.

Therefore, the flame propagation becomes unstable, and there is a possibility that blowout will occur immediately after ignition.

[Means for Solving Problems] An object of the present invention is to solve the above problems, and the present invention has a fuel injection nozzle disposed substantially on the axial center of a combustion chamber recessed in a piston. The nozzles are formed with injection holes for supplying the fuel spray to the inner peripheral wall of the combustion chamber at intervals in the circumferential direction, and the intervals at which these injection holes are formed are sequentially increased in the swirl direction so that the fuel spray on the upstream side in the swirl direction is increased. The spark assist diesel engine is configured by arranging ignition means in the.

[Operation] Since the spray angle of the fuel spray injected toward the inner peripheral wall into the combustion chamber is sequentially expanded in the swirl direction, immediately after the injection, the ignition means is ignited between the adjacent fuel sprays. An air-fuel mixture is generated that propagates a flame to each spray during. Therefore, when the ignition means is ignited, the flame is surely propagated to the downstream side in the swirl direction, so that the combustion is stabilized and the output performance is improved.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

 1 shown in FIG. 1 is a piston.

A combustion chamber 3 having a circular horizontal cross section is formed on the top surface 2 of the piston 1 so as to be recessed downward in the axial direction. At a substantially axial position of the combustion chamber 3, alcohol in the combustion chamber 3 is formed. ，
A fuel injection nozzle 4 is provided for supplying a spray of a low cetane number fuel such as methanol.

In the embodiment, the fuel injection nozzle 4 is formed by opening a plurality of injection holes in the injection hole portion 6 which forms the tip of the nozzle body 5, as shown in FIGS.

The number of nozzles formed in the embodiment is 6, and the number of nozzles 7 is 7
The formation positions of ~ 12 are determined such that a large number of injection holes 7-12 face relatively to one side of the combustion chamber and the distance between adjacent injection holes in the swirl S direction is sequentially increased.

In other words, the spray angles θ formed by the adjacent fuel sprays of the fuel sprays F _{1 to} F ₆ that are respectively injected from the injection ports 7 to 12 and reach the inner peripheral wall 3a of the combustion chamber 3 are sequentially arranged in the swirl direction. The opening positions of the injection holes 7 to 12 are set at positions where they are enlarged.

That is, if the spray angle on the most upstream side in the swirl direction is θ ₁ , and in the following swirl direction order θ ₂ , θ ₃ ... θ ₅ , then θ ₁ <
It is determined so as to satisfy θ ₂ <θ ₃ <θ ₄ <θ ₅ .

However, each of the spray angles θ _{1 to} θ ₅ is a rare zone at least during the ignition timing and between the air-fuel mixtures produced by the injected fuel sprays F ₁ -F ₆ or between the air-fuel mixture and the fuel spray. Does not exist, that is, after being ignited, the spray angles θ _{1 to} θ ₅ are set so that flame propagation can be reliably performed in the forward direction of the swirl S.

In such a configuration, the spark plug 13 as the ignition means
Locates the discharge part 13a near the inner peripheral wall 3a of the combustion chamber 3 and, in the embodiment, the discharge part 13a is in the region of the spray angle θ _1.
13a is located.

By the way, in the embodiment, in order to positively promote the generation of the air-fuel mixture so that the flames of the air-fuel mixture are propagated between the fuel sprays F _{1 to} F ₆ , the injection ports 7 to 12 are The nozzle diameter d of is determined as follows.

As shown in FIG. 3, the nozzle diameter of the nozzle 7 is d ₁ , the nozzle diameter of the nozzle 8 is d ₂ , the nozzle diameter of the nozzle 9 is d ₃ , the nozzle diameter of the nozzle 10 is d ₄ , and the nozzle diameter of the nozzle 11 is d. ₅ , the nozzle diameter of nozzle 12 is d ₆
As d ₁ <d ₂ <d ₃ <d ₄ <d ₅ <d ₆ .

However, in this case, since the particle diameter of the fuel injected from each nozzle increases according to the diameter of the nozzle and the penetration force increases, it is necessary to correct the spray angles θ _{1 to} θ ₅ . Or upstream side of the swirl S, since the generation of the gas mixture to the particle diameter of the fuel with respect to the downstream small downstream side is faster, the spray angle theta ₁ through? For the case where the nozzle hole diameter to the same ₅ is corrected to be smaller.

Therefore, between the fuel sprays F _{1 to} F ₆ injected from the respective injection ports 7 to 12, immediately after the injection until immediately before the ignition, there is no rare zone having a large air-fuel ratio and the spark plug is present.
Ignition of 13 satisfactorily ignites and spreads the flame. As a result, the air utilization rate is increased, combustion is stabilized, and the output and fuel consumption are improved.

By the way, the combustion chamber may have a rectangular horizontal cross section as shown in FIG.
It is provided in. That is, the provision of the spark plug 13 in the corner portion 15 is because the turbulent flow R generated in the corner portion 15 promotes the generation of the air-fuel mixture of the fuel spray F ₁ supplied upstream of the spark plug 13.

[Effects of the Invention] As is clear from the above description, according to the present invention, the following excellent effects are exhibited.

In the fuel injection nozzle, which is formed substantially in the axial center of the combustion chamber recessed in the piston, injection holes for ejecting fuel spray to the inner peripheral wall of the combustion chamber are formed at intervals in the circumferential direction, and the intervals at which these injection holes are formed. Since the ignition means is arranged between the fuel sprays on the upstream side in the swirl direction, the ignition is ignited between the upstream side and the downstream side of the swirl by the ignition of the ignition means, and the flame along the swirl direction. It has an excellent effect that the air-fuel mixture to be propagated can be surely generated and distributed.

[Brief description of drawings]

FIG. 1 is a top view showing a preferred embodiment of the present invention, FIG. 2 is a sectional view of a fuel injection nozzle, and FIG. 3 is III-III of FIG.
FIG. 4 is a top view showing another shape of the combustion chamber and the disposition positions of the fuel injection nozzle and the spark plug, and FIG. 5 is an internal combustion engine studied for burning low cetane number fuel. FIG. In the figure, 1 is a piston, 3 is a combustion chamber, 4 is a fuel injection nozzle, 7 to 12 are injection holes, S is a swirl, and θ _{1 to} θ ₅ are spray angles.

Claims (1)

(57) [Claims] 1. A fuel injection nozzle is arranged on the piston about the axial center of a combustion chamber, and the fuel spray is supplied to the inner peripheral wall of the combustion chamber at a circumferential interval. A spark-assist diesel engine in which injection holes are formed, the intervals at which the injection holes are formed are sequentially increased in the swirl direction, and ignition means is arranged between fuel sprays on the upstream side in the swirl direction.