JP2001082150A - Combusion camber of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate the mixing of fuel and air by providing a central projecting part at the bottom of a combustion chamber, a wall surface projecting part on the wall surface, a radially outwardly expanded recessed part, and an annular projecting part toward the radial inside in an opening part of the combustion chamber, and making the maximum diameter of the combustion chamber and the diameter of a piston have a specified relationship. SOLUTION: A central projecting part 1 is provided at the center of the bottom of a combustion chamber 100. Some of jet fuel 7 sprayed toward the wall surface projecting part 4 of a wall surface 3 flows to a recessed part 5 taking the wall surface projecting part 4 as a boundary, and the remaining part flows downward from the wall surface projecting part 4. The fuel which has flowed the recessed part 5 is restrained from flowing out to a squish area by an annular projecting part 6 to cause convection in the recessed part 5. The fuel becomes fine particles to be diffused over the peripheral area of the combustion chamber 100, thereby restraining diffusion to the bottom of the combustion chamber. The value obtained by dividing the maximum diameter d1 of the combustion chamber by a piston diameter D is set larger than 0.5. Thus, after the jet fuel 7 collides with the wall, the dynamic energy of the fuel itself is lowered so that mixing is accelerated by air current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber of a reentrant type diesel engine (the maximum diameter of the combustion chamber is larger than the opening diameter of the combustion chamber).

[0002]

2. Description of the Related Art In a conventional combustion chamber of a reentrant diesel engine, if the fuel injection timing is delayed, the fuel is injected with a large swirl (air flow) in the early stage and the middle stage of combustion, and the fuel and air are mixed. And the combustion proceeds satisfactorily, but the latter stage of combustion, that is, when the crank angle is 20
At ~ 30 degrees, the swirl ratio attenuates as shown in FIG.
Mixing of fuel and air does not proceed, and as shown in FIG. 3, the smoke relative value increases, and black smoke is easily generated.

[0003]

SUMMARY OF THE INVENTION The present invention provides a combustion chamber of a diesel engine in which fuel and air are mixed well over the entire period from the early stage of combustion to the late stage of combustion, and good combustion is performed. It is intended to be.

[0004]

According to a first aspect of the present invention, in a reentrant type combustion chamber, a central projection is provided at the center of the bottom of the combustion chamber, and is provided on a wall of the combustion chamber within a range where fuel is injected from a fuel injection nozzle. Providing an annular wall projection, providing a recess extending radially outward above the wall projection,
An annular protrusion directed inward in the radial direction was provided at the opening of the combustion chamber, and when the maximum diameter of the combustion chamber was d ₁ and the diameter of the piston was D, the relationship of d ₁ /D>0.5 was satisfied. In the invention of claim 2, in the reentrant combustion chamber, a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on the combustion chamber wall within a range where fuel is injected from the fuel injection nozzle, A recess extending radially outward is provided above the wall projection, an annular projection is provided at the opening of the combustion chamber inward in the radial direction, and a distance from the bottom of the combustion chamber to the wall projection is h, If the combustion chamber depth is H, 0.5
<H / H <0.7. According to the invention of claim 3, in the reentrant combustion chamber, a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on a wall of the combustion chamber within a range where fuel is injected from a fuel injection nozzle. A radially outwardly extending recess is provided above the wall projection, an annular projection is provided at the opening of the combustion chamber inward in the radial direction, the diameter of the combustion chamber opening is d, and the maximum diameter of the recess is Is defined as d ₂ , the relationship d <d ₂ <d ₁ was satisfied. According to the invention of claim 4, in the reentrant combustion chamber, a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on the combustion chamber wall within a range where fuel is injected from the fuel injection nozzle. Assuming that a concave portion extending radially outward is provided above the wall surface protrusion portion, an annular protrusion portion extending inward in the radial direction is provided at the opening of the combustion chamber, and the diameter of the opening portion of the combustion chamber is d, then d / D < 0.5 was satisfied. According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the invention, the chamfered annular projection is provided at the opening of the combustion chamber. According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the bottom of the combustion chamber and the central projection are connected by a smooth curved surface. In the invention of claim 7, claims 1 to 6
In any one of the inventions described above, the height and the diameter of the central projection at the bottom of the combustion chamber are set to a height and a diameter that do not directly interfere with the fuel sprayed from the injection nozzle.

[0005]

1 is a schematic sectional view of a combustion chamber 100 of a direct injection diesel engine according to the first to seventh aspects of the present invention. Combustion chamber 100 is re-entrant (small opening diameter d of the combustion chamber than the combustion chamber maximum diameter d _1).

As shown in FIG. 1, at the center of the bottom of the combustion chamber 100, the height from the bottom 8 is h ₁ (distance h ₁ ) and the diameter is d _3.
Center projection 1 is provided. The central projection 1 and the wall 3
They are connected by a smooth curved surface forming the bottom 8. An annular wall surface projection 4 is provided on the wall surface 3 at a position where the height from the bottom 8 is h (distance h).

[0007] At the opening of the combustion chamber 100, there is provided an annular projection 6 which faces inward in the radial direction. As shown in FIG. 1, the annular projection 6 is chamfered. Between the annular projection 6 and the wall projection 4, a depression 5 is formed which extends radially outward. The injected fuel 7 is injected from the fuel injection nozzle 2 toward the wall surface projection 4.

FIG. 4 is a schematic cross-sectional view (hatching is omitted) comparing the shapes of a combustion chamber 100 (shown by a solid line) and a conventional reentrant combustion chamber (shown by a broken line) of Japanese Patent Laid-Open No. 5-106443. is there. In the combustion chamber 100, as shown by the arrow 1a, the central projection 1 projects radially outward from the conventional combustion chamber, and the wall surface 3 also expands radially outward as shown by the arrow 3a. As shown, the opening protrudes radially inward by forming an annular projection 6.

FIGS. 6A to 6C are schematic cross-sectional views showing the state of diffusion of the fuel injected in the combustion chamber 100. FIG.
As shown in FIG. 6A, the injected fuel 7 is sprayed toward the wall surface projection 4 of the wall surface 3. As shown in FIG. 6B, after the injected fuel 7 is sprayed on the wall surface 3,
Part of the flow flows to the concave portion 5 with the boundary as, and the rest flows downward from the wall surface projection 4.

The fuel that has flowed into the depression 5 is
As a result, the outflow to the squish area 9 (the area between the cylinder head and the piston 10 not shown) is suppressed, and the convection flows in the recess 5. As shown in FIG.
Injected fuel 7 sprayed on the surface of the combustion chamber 100 becomes fine particles and diffuses around the peripheral area of the combustion chamber 100, thereby suppressing diffusion to the bottom of the combustion chamber.

FIGS. 7 (a) to 7 (c) show FIGS.
FIG. 4 is a schematic cross-sectional view showing a state of diffusion of injected fuel in a conventional reentrant combustion chamber corresponding to (c) of Japanese Patent Application Laid-Open No. 5-106443. 7A, the injected fuel blown to the wall surface flows downward in the combustion chamber as shown in FIG. 7B, and the spray fuel is biased toward the bottom of the combustion chamber as shown in FIG. 7C. Good mixing of air and fuel is inadequate. Since the air flow is poor at the bottom of the combustion chamber, the air and the fuel are hardly mixed, and the fuel burns in an excessively rich state, so that black smoke is easily generated.

FIG. 2 is a graph comparing the relationship between the swirl ratio and the crank angle between the combustion chamber 100 according to the present invention (the first to seventh aspects of the present invention) and the conventional combustion chamber. As shown in FIG. 2, in the conventional combustion chamber, the swirl ratio is attenuated in the latter stage of combustion in which the crank angle is advanced, but in the combustion chamber 100 of the present invention, the swirl ratio retention rate is high even at a crank angle of 30 ° or more. . Therefore, in the combustion chamber 100 of the present invention, the fuel and the air are favorably mixed not only in the early stage of the combustion but also in the latter stage of the combustion.

FIG. 3 is a graph comparing the relationship between the relative smoke value and the fuel injection timing between the combustion chamber 100 according to the present invention and the conventional combustion chamber. As shown in FIG. 3, as the fuel injection timing is delayed, the smoke relative value is improved in the conventional combustion chamber. However, in the combustion chamber 100 of the present invention, even if the fuel injection timing is delayed, the smoke relative value is almost improved. Can not be seen. Therefore, the combustion chamber 100 according to the present invention
Is less likely to generate black smoke than a conventional combustion chamber.

FIG. 5 is a graph comparing the engine output of the combustion chamber 100 and each coefficient according to the present invention. From the graph shown in FIG. 5, in order to increase the engine output, each coefficient (d /
D, d ₁ / D, h / H) can be determined as follows.

The value d / D obtained by dividing the opening diameter d by the piston diameter D is made smaller than 0.5. The value d ₁ / D obtained by dividing the combustion chamber maximum diameter d ₁ by the piston diameter D is set to be larger than 0.5. A value h / H obtained by dividing the distance h from the bottom 8 to the wall projection 4 by the combustion chamber depth H is set between 0.5 and 0.7. If each coefficient is set as described above, an improvement in engine output can be expected.

After the injected fuel 7 collides with the wall (late stage of combustion)
Since the kinetic energy of the fuel itself is reduced, the swirling (air flow) promotes the mixing.

In the above description, the bottom of the combustion chamber 100 in FIG. 1 is defined as the bottom, and the side of the annular projection 6 is defined as the top. However, the piston 10 as shown in FIG. It is not limited to the case where the cylinder (not shown) is installed in the direction, and the cylinder may be installed and used in a horizontal direction or an oblique direction.

[0018]

According to the first to fourth aspects of the present invention, the provision of the recessed portion 5 allows a part of the injected fuel 7 to convect in the recessed portion 5, thereby suppressing combustion at the beginning of combustion.
Since the combustion temperature in the initial stage of combustion does not become excessively high and rapid combustion can be avoided, the generation of nitrogen oxides can be suppressed.

As the crank angle increases, the piston 10 descends, and the air flows into the combustion chamber 100 from the squish area 9, so that the swirl increases in the latter stage of the combustion, and the fuel convected in the recess 5 mixes well with the air. Also, the air-fuel mixture can be satisfactorily burned even in the latter stage of the combustion.

Since the squish area 9 is relatively low in temperature, good combustion cannot be performed, and the combustion in the squish area 9 causes black smoke. Therefore, it is not preferable for the fuel to flow out to the squish area 9, but in the invention of claim 1, the annular projection 6 that protrudes inward in the radial direction is provided at the opening of the combustion chamber 100 so that
The fuel that has collided with the squish area 9 can be prevented from flowing out.

If the injection timing is delayed, black smoke is generally likely to be generated. However, in the combustion chamber 100 of the present invention, even when the injection timing is delayed, the swirl ratio is kept large in the later stage of the combustion, so that good combustion is achieved. And the generation of black smoke can be suppressed.

According to the first aspect of the present invention, the combustion chamber maximum diameter d
_Since the value obtained by dividing ₁ by the piston diameter D is set to 0.5 or more, the kinetic energy of the injected fuel 7 promotes the mixing of fuel and air in the early stage of combustion, and the fuel after the injected fuel 7 collides with the wall surface 3. Since the swirl (air flow) at the bottom portion 8 is kept high without being attenuated in the latter stage of the combustion in which the evaporation of the fuel has progressed to some extent, the mixing of the fuel and the air can be promoted.

According to the second aspect of the present invention, the value obtained by dividing the height (distance h) of the wall surface projection 4 by the depth H of the combustion chamber 100 is 0.5 or more and 0.7 or less. Therefore, the injected fuel 7 can be dispersed vertically by the wall projections 4 and can be efficiently burned from the initial stage of combustion to the latter stage of combustion.

According to the third aspect of the invention, since the opening diameter d is set so that the opening diameter d <the maximum diameter d _{2 of the} hollow portion <the maximum diameter d _{1 of the} combustion chamber, the fuel is appropriately dispersed vertically by the wall surface projections 4. In the combustion chamber 100, it is possible to satisfactorily mix with air and burn over the entire region from the early stage to the late stage of combustion.

According to the present invention, d / D <0.5
By setting to, it is possible to favorably prevent the fuel from flowing into the squish area 9.

According to the fifth aspect of the present invention, by chamfering the annular projection 6, the air resistance at the time of inflow of air from the squish area 9 into the combustion chamber 100 at the latter stage of combustion is reduced, and the air is burned at the latter stage of combustion. Room 10
Since the fuel easily flows into the inside of the fuel cell, the fuel and the air are easily mixed, and good combustion can be performed.

According to the sixth aspect of the present invention, by connecting the bottom portion 8 of the combustion chamber and the central projection 1 with a smooth curved surface, the swirl is not attenuated at the bottom portion 8 and an environment where fuel and air are easily mixed is maintained. The air can be satisfactorily burned.

According to the seventh aspect of the present invention, by setting the size of the central projection 1 such that the injected fuel 7 injected from the fuel injection nozzle 2 does not collide, the injected fuel 7 can collide with the wall surface 3. The fuel can be smoothly convected in the combustion chamber 100.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a combustion chamber of a direct injection diesel engine according to the first to seventh aspects of the present invention.

FIG. 2 is a graph comparing the relationship between the swirl ratio and the crank angle in the combustion chamber according to the first to seventh aspects of the present invention and a conventional combustion chamber.

FIG. 3 is a graph comparing the relationship between the relative smoke value and the fuel injection timing in the combustion chamber according to the first to seventh aspects of the present invention and a conventional combustion chamber.

FIG. 4 is a schematic cross-sectional view comparing the shapes of a combustion chamber of a direct injection diesel engine according to the invention of claims 1 to 7 and a conventional reentrant combustion chamber.

FIG. 5 is a graph comparing the engine output of the combustion chamber and each coefficient according to the present invention.

FIGS. 6A to 6C are schematic cross-sectional views showing diffusion states of fuel injected in a combustion chamber.

7 (a) to 7 (c) are schematic cross-sectional views showing diffusion states of injected fuel in a conventional reentrant combustion chamber corresponding to FIGS. 6 (a) to 6 (c).

[Explanation of symbols]

Reference Signs List 1 central projection (central projection) 2 fuel injection nozzle 3 wall surface 4 wall projection 5 recess 6 annular projection 7 injected fuel 8 bottom 9 squish area 10 piston d opening diameter d ₁ maximum diameter of combustion chamber d ₂ maximum of recess Diameter d ₃ Center protrusion diameter D Piston diameter h Distance from combustion chamber bottom to wall protrusion h ₁ Center protrusion height H Fuel chamber depth

Claims (7)

[Claims] In a reentrant combustion chamber, a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on a wall of the combustion chamber within a range where fuel is injected from a fuel injection nozzle. part upward the recess extends provided radially outward of the annular projection toward the radially inward opening of the combustion chamber is provided, the combustion chamber maximum diameter and d _1, the diameter of the piston is D, A combustion chamber for a direct-injection diesel engine, which satisfies a relationship of d ₁ /D>0.5. 2. A reentrant combustion chamber, wherein a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on a wall of the combustion chamber within a range where fuel is injected from a fuel injection nozzle. A recess extending radially outward above the portion, an annular projection extending radially inward at the opening of the combustion chamber, a distance from the bottom of the combustion chamber to the wall projection being h, If the depth is H, 0.5
<H / H <0.7, a combustion chamber of a diesel engine. 3. A reentrant type combustion chamber, wherein a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on a wall of the combustion chamber within a range where fuel is injected from a fuel injection nozzle. Providing a recess extending radially outward above the portion, providing an annular protrusion directed radially inward at the opening of the combustion chamber, and defining the diameter of the opening of the combustion chamber as d,
A combustion chamber for a diesel engine, wherein d <d ₂ <d ₁ where d ₂ is the maximum diameter of the recess. 4. In a reentrant combustion chamber, a central projection is provided at the center of the bottom of the combustion chamber, and an annular wall projection is provided on a wall of the combustion chamber within a range where fuel is injected from a fuel injection nozzle. A concave portion extending radially outward is provided above the portion, and an annular projecting portion extending radially inward is provided at the opening of the combustion chamber. When the diameter of the opening of the combustion chamber is d, d / D <0. 5. A combustion chamber for a diesel engine, wherein the combustion chamber is 5. 5. The combustion chamber of a diesel engine according to claim 1, wherein an annular projection with a chamfer is provided at an opening of the combustion chamber. 6. The combustion chamber of a diesel engine according to claim 1, wherein the bottom of the combustion chamber and the central projection are connected by a smooth curved surface. 7. The diesel engine according to claim 1, wherein the height and diameter of the central projection at the bottom of the combustion chamber are set to a height and diameter that do not directly interfere with fuel sprayed from the injection nozzle. Combustion chamber.