JPH0247232Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a combustion chamber of a uniflow two-stroke diesel engine.

[Conventional technology]

Figures 3 and 4 show the combustion chamber structure of a conventional uniflow scavenging two-stroke engine.

1 is a piston, 2 is a piston rod, 3 is a cylinder, 4 is a cylinder cover, 5 is an exhaust valve box, 6 is an exhaust valve, 7 is a fuel injection valve, and 8 is a combustion chamber.

When piston 1 approaches bottom dead center, the exhaust valve opens,
When the exhaust gas flows out through the exhaust valve 6 and the exhaust pressure decreases, fresh air flows in from a scavenging hole (not shown) drilled in the lower part of the cylinder, and the residual exhaust gas in the cylinder 3 is expelled from the exhaust valve 6. At the same time as scavenging, the cylinder 3 is filled with fresh air. At this time, in order to achieve good combustion, scavenging holes are provided in the direction in which strong vortices are generated within the cylinder. Next, when the piston 1 rises from the bottom dead center and closes the scavenging hole, compression begins, and as the piston 1 reaches near the top dead center as shown in the figure, the air in the combustion chamber 8 becomes high temperature and high pressure. High-pressure fuel is injected from the fuel injection valves 7 provided on both sides of the cylinder cover 4, atomizes the high-temperature, high-pressure compressed air, forms a spray stream, penetrates the compressed air, and is dispersed within the combustion chamber. Ru. At this time, the vortex flow given during the scavenging described above remains with almost no attenuation even when the piston approaches top dead center, and the injected fuel and air are sufficiently mixed and good combustion occurs, causing the cylinder to move forward. The structure is such that the internal pressure increases, strongly pushing down the piston and generating rotational force.

[The problem that the idea attempts to solve]

However, as shown in Figure 4, conventional combustion chambers have a disk-like or hemispherical shape, so the vortices become too strong at high speeds, making it difficult to effectively utilize the vortices and to utilize the air in the combustion chamber for combustion. It is insufficient in this respect. That is, since the vortex flow is generally a rigid vortex, it is weak at the center of the combustion chamber, and in a disk-shaped or hemispherical combustion chamber, it is considered difficult to utilize the air in the center due to the spray movement caused by fuel injection.

The purpose of this invention is to create turbulence in the air flow near the wall of the combustion chamber near the top dead center at the end of the compression stroke of a diesel engine, and to promote the mixing of fuel and air, especially on the wall and the center of the combustion chamber. An object of the present invention is to provide a combustion chamber for a diesel engine with improved combustion efficiency.

[Means to solve the problem]

The combustion chamber of the diesel engine according to the present invention is
In a uniflow type two-stroke diesel engine, which has one exhaust valve at the center of the top of the cylinder cover and a plurality of fuel valves around the exhaust valve, and forms at least one spray in the direction of the air swirl, the cylinder A combustion chamber formed at a predetermined depth within the cover has a polygonal cross-sectional shape perpendicular to the cylinder axis at least in the vicinity of the cylinder side opening.

[Effect]

In the combustion chamber of the diesel engine of the present invention, the shape of the combustion chamber is equilateral, scalene polygonal prism, or truncated polygonal pyramid, which causes turbulence in the air flow near the combustion chamber wall at the end of the compression stroke, causing air flow toward the center of the combustion chamber. The air-fuel mixture also flows, promoting the mixing of fuel and air near the wall and the use of air in the central part of the combustion chamber, improving combustion efficiency and increasing output.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

Here, the same or equivalent components as those of the conventional device will be described using the same reference numerals.

The uniflow type two-stroke diesel engine of the present invention has one exhaust valve at the center of the top surface of the cylinder cover and a plurality of fuel valves around the exhaust valve, and two fuel valves that spray in the direction of the air vortex. is formed.

In FIG. 1, 1 is a piston, 2 is a piston rod, 3 is a cylinder, 41 is a cylinder cover, 5 is an exhaust valve box, 6 is an exhaust valve, 7 is a fuel (injection) valve, 8
is the combustion chamber. In the embodiment of the present invention for this uniflow type two-stroke diesel engine, the exhaust valve 6 of the cylinder cover 41 opens at the end of the explosion stroke to exhaust the combustion gas, and at the same time, the residual combustion gas is removed from the scavenging hole (not shown) at the bottom of the cylinder. At the same time, the cylinder is filled with fresh air as it is expelled by fresh air flowing in. At this time, the fresh air from the scavenging holes generally generates a strong vortex within the cylinder in order to improve scavenging efficiency and combustion efficiency. This vortex remains in the combustion chamber even when the piston 1 is at the top dead center at the end of the compression stroke, promoting the mixing of the fuel and air injected at high pressure and high speed from the fuel injection valve 7, resulting in good combustion. However, in the embodiment of the present invention, the shape of the combustion chamber wall formed within the cylinder cover 41 is equal-sided, as shown in FIG. It is formed in the shape of a scalene polygon or a truncated polygonal pyramid. Therefore, the air compressed by the piston 1 rising during the compression stroke enters the combustion chamber 8 having the above-mentioned shape near the top dead center, as shown in FIG. At this time, the compressed air has a circulation flow given during scavenging, but in this embodiment, the wall surface of the combustion chamber 8 is not in the shape of a disk or hemisphere as in the conventional example, but in the shape of a polygonal column or a truncated polygonal pyramid. Therefore, the air flow is turbulent on this wall surface, and at the same time an air flow is also generated toward the center of the combustion chamber 8, and the fuel is injected from the fuel injection valve 7 installed on the side of the combustion chamber 8 near the top dead center. Of the fuel that has reached near the wall surface, it is sufficiently mixed with air, and the air in that area is also fully utilized by the flow of the air-fuel mixture to the center of the combustion chamber 8, resulting in complete combustion within the cylinder 3. can be realized.

In the above embodiments, the present invention is applied to a uniflow type two-stroke engine, but the present invention is applicable to all diesel engines in which the combustion chamber 8 is formed within the cylinder cover 41, and the present invention is the same. The action and effect can be obtained.

[Effect of idea]

As described above, the combustion chamber of the diesel engine according to the present invention has an equilateral, scalene polygonal prism, or truncated polygonal pyramid shape, so that the combustion chamber formed in the cylinder cover is close to the combustion chamber wall surface at the end of the compression stroke. This causes turbulence in the airflow of the combustion chamber, which causes the mixture to flow toward the center of the combustion chamber, promoting the mixing of fuel and air near the wall and the use of air in the center of the combustion chamber, improving combustion efficiency and increasing output. The effect of increasing is extremely large.

[Brief explanation of drawings]

Figures 1 and 2 show embodiments of the present invention;
The figure is a sectional view of the main parts around the combustion chamber of a uniflow scavenging type two-stroke diesel engine, Figure 2 is a cross-sectional view of Figure 1, Figures 3 and 4 are related to conventional equipment, and Figure 3 is a uniflow scavenging type two-stroke diesel engine. FIG. 4 is a cross-sectional view of the main parts around the combustion chamber of a scavenging two-stroke diesel engine. 3...Cylinder, 8...Combustion chamber, 41...Cylinder cover.

Claims (1)

[Scope of utility model registration request] In a two-stroke diesel engine that is equipped with one exhaust valve at the center of the top of the cylinder cover and a plurality of fuel valves around the exhaust valve and forms at least one spray in the direction of the air swirl, 1. A combustion chamber for a diesel engine, wherein the combustion chamber is formed with a predetermined depth and has a polygonal cross-sectional shape perpendicular to the cylinder axis at least in the vicinity of the cylinder side opening.