JPH0826770B2 - Combustion chamber of direct injection diesel engine - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a combustion chamber of direct-injection diesel engine in order to significantly reduce the NO _X (nitrogen oxides) while maintaining the generation of smoke at a low level.

[0002]

2. Description of the Related Art At present, reduction of smoke and NO _x is an important issue in diesel engines, and in order to reduce them, high pressure injection, improvement of combustion system, exhaust gas recirculation (EG
Various proposals such as R) have been made. EGR
Have problems of durability and reliability such as deterioration of fuel consumption and smoke, corrosion of EGR device due to exhaust gas or deterioration of function.

From the viewpoint of the combustion system, in the case of low pressure injection which is widely used at present, after the spray is ignited in the vicinity of the nozzle, it progresses while being wrapped in the whole flame. At this time, the spray is air. At the same time, it burns while energizing the burnt gas generated by itself, so a high temperature part and an oxygen deficient part are formed in the center of the spray, which becomes a cause of smoke generation,
It is said that the burning of burned gas acts as a negative factor. Therefore, in order to reduce smoke, it is necessary to mix fuel and air quickly, and methods such as swirl and squish are used to improve the air utilization rate. Since the mixing speed also increases, there is a contradictory problem that the heat generation rate in the early stage of combustion increases due to the increase in premixed combustion, leading to an increase in NO _X , which makes it difficult to reduce smoke and NO _X simultaneously. ing.

In order to solve the above problems, there is known a system in which a high pressure injection (for example, an injection pressure of 1000 kg / cm ² or more), a small injection hole nozzle, a shallow dish combustion chamber and a low swirl are combined. This will be described with reference to FIG. 13. 1 is a piston, 2 is a piston ring, 3 is a cylinder liner, 4 is a gasket, 5 is a cylinder head, and 6 is a fuel injection valve having a nozzle 7. A chamber 9 is formed. When the piston 1 rises and reaches the vicinity of the top dead center, the spray F of the fuel injected from the nozzle 7 ignites at once in the vicinity of the wall surface 10, and then the flame H expands toward the center of the combustion chamber 9, Since the energy of the spray is large, the central part remains as a non-combustible area until the end of injection. That is, the spray progresses while sufficiently entraining air in the non-combustible region side near the center of the combustion chamber 9 until it reaches the wall surface 10.
On the 0 side, since the burner gas is introduced and it follows the two-stage combustion path where it collides with the wall surface 10, the smoke is low, and even if the injection timing is greatly delayed, it ignites, so in combination with the injection timing delay, low pressure injection It is possible to reduce the smoke and the NO _{X at} the same time as compared with the above.

[0005]

However, at present, the utilization of air (oxygen) in the combustion chamber is not sufficient, and there is a problem that smoke is generated and discharged, especially when the load is high (fuel injection amount is large). ing. To suppress smoke,
Activates diffusion combustion and maintains strong turbulence until the latter stage of combustion,
Furthermore, it is necessary to keep the turbulent vortices in a fine state.
However, since diffusion combustion occurs in the expansion stroke, the air flow in the cylinder is generally attenuated at that point, and the effect of combustion activation due to turbulence such as intake swirl given during the compression stroke becomes relatively small. Also, in the case of high pressure injection, the turbulence intensity of the flame is high at the beginning of diffusion combustion,
In the latter stage of combustion, it decays and does not differ much from low-pressure injection.

In order to solve this, a combustion disturbance chamber is provided in the cylinder head, a small amount of fuel is injected into this chamber in the latter stage of combustion, and the high pressure combustion gas generated in the chamber is jetted into the combustion chamber. Although a method of directly injecting CO gas into the combustion chamber has been proposed, it has a problem that the device becomes complicated and becomes large in size.

In order to solve this problem, the present inventor has
An experiment was conducted to observe the concentration distribution inside the spray using the fuel injection valve. FIG. 14 is a schematic configuration diagram of the experimental device,
111 is a high pressure container, 112 is an observation window, 113 is a fuel injection valve, 114 is a vacuum pump, 115 is a nitrogen gas cylinder,
116 is an image conversion camera, 117 is a fuel supply device,
118 is an injection control device, 119 is a laser control device, 12
Reference numeral 0 represents a copper vapor laser, and by irradiating the spray injected into the high-pressure container 111 with laser light, the concentration distribution inside the spray was observed from the state of scattered light.

FIG. 15 is a diagram for explaining the spray state. The structure and phenomenon of the spray are roughly divided into four regions, and in region I, the spray goes straight with high concentration and hardly spreads, and in region II, it goes straight. Things began to meander insecurely, Region III
Then, as the meander deforms to form a branch structure, the branches change intervals, repeat division and coalescence, or gradually drop droplets from the surroundings. In Region IV, the branch structure is no longer present and each fringe is affected by the vortex generated between it and the surrounding gas, and exhibits unique behavior and a complicated distribution. Thus, the inside of the spray is very non-uniform, and several high-density stripes of droplets are seen, and this non-uniform high-density portion leads to the production of a large amount of smoke.

In the above experiment, it was found that when a wire net was placed in the spray, a large turbulence was generated in the spray, a high-concentration fringe was small, and the spray was also spread widely. In other words, the concentration distribution is almost uniform, and a large amount of ambient gas is taken in, so that the concentration becomes low.

The present invention solves the above problems and problems, and promotes the turbulence of the spray and the turbulence of the flame at the same time, thereby activating the mixing of the spray and the air, thereby causing the generation of smoke. An object of the present invention is to provide a combustion chamber of a direct injection diesel engine capable of significantly reducing NO _X while maintaining the low level.

[0011]

For this purpose, the combustion chamber of the direct injection type diesel engine of the present invention is provided with a fuel injection valve 6 provided on a cylinder head 5 and a nozzle 7 of the fuel injection valve 6.
A plurality of injection holes, a combustion chamber 1b formed so as to have a depression in the upper portion of the piston 1, and the combustion chamber 1b.
A plurality of intermediate walls 1c standing on the combustion chamber so as to surround the nozzle 7 between the outer peripheral wall 1a and the injection holes, and a mesh member 11 provided between the intermediate walls. It is characterized in that the spray injected from the holes collides with the mesh member 11. The mesh member may have a cylindrical shape or a box shape, or a horizontal mesh member may be added to the upper surface of the piston 1. Here, the numbers added to the above configuration are for comparison with the drawings in order to facilitate understanding of the present invention, and the configuration of the present invention is not limited thereby.

[0012]

In the present invention, for example, as shown in FIG.
The spray injected from the injection hole of the nozzle 7 is the mesh member 1
1 to generate a large turbulence in the spray, promote the mixing with air, and collide with the outer peripheral wall 1a to ignite and burn. Further, as shown in FIG. 4, the fuel injected from the injection hole of the nozzle 7 collides with the mesh member 11 from the A direction,
After generating a large turbulence in the spray and promoting mixing with air, after colliding with the outer peripheral wall 1a and igniting and burning, the flame spreads in the left and right B and C directions, and at the same time, the cylinder head 5 in the D direction. By spreading to the side and passing through the mesh member 11 again, the turbulence of the flame is promoted, the mixture of the flame and air is activated, and the smoke is suppressed to a low level.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a combustion chamber of a direct injection type diesel engine of the present invention. FIG. A is a perspective view and FIG. B is B of FIG.
It is sectional drawing seen in the arrow direction along the -B line.

Reference numeral 1 is a piston, 2 is a piston ring, 3 is a cylinder liner, 4 is a gasket, 5 is a cylinder head, 6 is a fuel injection valve having a nozzle 7, and the nozzle 7 is a nozzle.
Has a plurality of injection holes for injecting fuel. The piston 1 includes an outer peripheral wall 1a formed at the top, a combustion chamber 1b formed so as to have a recessed portion inside thereof, and a plurality of concentrically erected on the combustion chamber 1b so as to surround the nozzle 7. The intermediate mesh wall 1c and the intermediate mesh wall 1c, and the mesh-like mesh member 11 is fixed between the intermediate walls 1c. And the nozzle 7
Each of the sprays injected from the injection holes of the mesh member 1
Arrange so as to collide with 1. The mesh member 11 is made of a material having heat resistance and durability such as stainless steel.

The operation of the present embodiment having the above-mentioned structure will be described. The spray injected from the injection hole of the nozzle 7 collides with the mesh member 11 to generate a large turbulence in the spray, which promotes mixing with air. However, since it collides with the outer peripheral wall 1a and is ignited and burned, the generation of smoke can be suppressed to a low level.

FIG. 2 shows another embodiment of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, and FIG. C is an exploded view of the mesh member. It is a perspective view. In the following embodiments, the same configurations as those of the embodiment of FIG. In this embodiment, the mesh member 11 has a cylindrical shape having a fixing flange 11a at the bottom, and the fixing flange 11a is formed.
Is fixed to the piston 1 by a fixing screw 13 via a fixing plate 12.

FIG. 3 shows a reference example of the present invention, FIG. A is a plan view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, and FIG. C is a perspective view. In this example, the piston 1
The main combustion chamber 1d is provided at the center of the main combustion chamber 1d, and a plurality of auxiliary combustion chambers 1e communicating with the main combustion chamber 1d are provided at the outer periphery of the main combustion chamber 1d.
An example in which the mesh member 11 is provided at the boundary between the d and the auxiliary combustion chamber 1e is shown.

FIG. 4 shows still another embodiment of the present invention,
FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A as seen in the direction of the arrow, FIG. C is a perspective view of a mesh member, and FIGS. D and E show other examples of the mesh member. It is a perspective view. In the present embodiment, the mesh member 11 has an arc-shaped box shape, has meshes on the side surface and the upper surface, and is arranged so that each spray ejected from the injection hole of the nozzle 7 collides with the mesh member 11. The mesh member 11 is provided with fixing flanges 11a and 11b in the front-rear direction, and the fixing flange 11a is fixed to the fixing screw 1 via the fixing plate 12.
3, the fixing flange 11b is fixed to the outer peripheral wall 1a of the piston 1 by the fixing screw 15 via the fixing ring 14. The mesh member 11 may have a box shape as shown in FIG. D, or may have a curved surface as the surface on which the spray hits, as shown in FIG. E.

The operation of this embodiment will be described. The spray injected from the injection hole of the nozzle 7 is as shown in FIG.
After colliding with the mesh member 11 from the A direction to generate a large turbulence in the spray and promoting mixing with air, the flame collides with the outer peripheral wall 1a and ignites and burns.
In the same direction, it spreads to the cylinder head side in the D direction and passes through the mesh member 11 again to accelerate the turbulence of the flame, activate the mixture of the flame and air, and suppress the generation of smoke to a low level.

FIG. 5 shows still another embodiment of the present invention,
FIG. A is a perspective view, FIG. B is a cross-sectional view taken along the line BB of FIG. A as seen in the direction of the arrow, and FIG. C is a perspective view of a mesh member. This embodiment is different from the embodiment of FIG. 3 in that the mesh member 1
The upper surface of 1 is a curved surface.

FIG. 6 shows still another embodiment of the present invention,
FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A as seen in the direction of the arrow, and FIG. C is an exploded perspective view. In this embodiment, the mesh member 11 having the mesh on the side surface and the upper surface is fixed to the ring-shaped fixed frame 17, and this is penetrated into the outer peripheral wall 1a of the piston 1, and the upper surface is fixed via the fixing ring 14. It is fixed by fixing screws 15.

FIG. 7 shows still another embodiment of the present invention,
FIG. A is a perspective view, FIG. B is a cross-sectional view taken along the line BB of FIG. A as seen in the direction of the arrow, and FIG. C is a perspective view of a mesh member. In the present embodiment, the mesh member 11 has a cylindrical mesh 11c on the inner peripheral side and a horizontal mesh 11d formed on the outer upper surface of the cylindrical mesh 11c, and the fixing flange 11a is fixed. It is fixed to the piston 1 by the fixing screw 13 via the plate 12, and the fixing flange 11
b is fixed to the outer peripheral wall 1a of the piston 1 by a fixing screw 15 via a fixing ring 14.

FIG. 8 shows a reference example of the present invention, FIG. A is a perspective view, and FIG. B is a sectional view taken along the line BB of FIG. This example shows an example in which the cylindrical mesh 11c of FIG. 6 is brought closer to the outer peripheral wall 1a side.

FIG. 9 shows still another embodiment of the present invention,
FIG. A is a perspective view, and FIG. B is a sectional view taken along the line BB in FIG. In this embodiment, a plurality of meshes 11e are provided in the radial direction inside the mesh member 11 of FIG.

FIG. 10 shows a reference example of the present invention, FIG. A is a perspective view, and FIG. B is a sectional view taken along the line BB of FIG. In this example, the mesh member 11 having a mesh stretched on the reinforcing stay 16 is attached to the piston 1
In this example, only when the piston 1 is moved up or down, the spray hits the mesh A portion to promote mixing, and the mesh in the portion B promotes upward turbulence of the flame.

FIG. 11 shows a reference example of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, and FIG. C is a perspective view of a mesh member. is there. This example shows an example of attaching the mesh member 11 to the reentrant piston.

FIG. 12 is a perspective view showing a reference example of the present invention. The fixing flange 1 is provided in the auxiliary combustion chamber 1e of the example of FIG.
An example is shown in which the tubular mesh member 11 provided in 1a is inserted and fixed with fixing screws 13.

[0028]

As is apparent from the above description, according to the present invention, the fuel is collided with the mesh member immediately after the spraying to promote the turbulence of the spray and at the same time to promote the turbulence of the flame, whereby the spray is produced. and intensified mixing of the air, while maintaining the generation of smoke at a low level, it is possible to significantly reduce the NO _X. Further, the spray is cooled by the mesh member, and the catalytic action of the mesh member is added, so that NO _X can be greatly reduced.

[Brief description of drawings]

1 shows an embodiment of a combustion chamber of a direct injection type diesel engine of the present invention, FIG. A is a perspective view, and FIG. B is a sectional view taken along the line BB of FIG. .

2 shows another embodiment of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, and FIG. C is an exploded perspective view of a mesh member. Is.

3 shows a reference example of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, FIG. C is a perspective view of a mesh member, and FIG. FIG. E is a perspective view showing another example of the mesh member.

4 shows another embodiment of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB in FIG. A in the direction of the arrow, and FIG. C is a perspective view of a mesh member. Is.

5 shows another embodiment of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, and FIG. C is an exploded perspective view. .

6 shows another embodiment of the present invention, FIG. A is a perspective view, FIG. B is a sectional view taken along the line BB of FIG. A in the direction of the arrow, and FIG. C is a perspective view of a mesh member. Is.

7 shows another embodiment of the present invention, FIG. A is a perspective view, and FIG. B is a cross-sectional view taken along the line BB of FIG.

8 shows a reference example of the present invention, FIG. A is a perspective view, and FIG. B is a cross-sectional view taken along the line BB of FIG.

9 shows another embodiment of the present invention, FIG. A is a perspective view, and FIG. B is a sectional view taken along the line BB of FIG.

10 shows a reference example of the present invention, FIG. A is a perspective view, and FIG.
Is a cross-sectional view taken along the line BB of FIG.
FIG. 4 is a perspective view of a mesh member.

11 shows a reference example of the present invention, FIG. A is a plan view, and FIG.
Is a cross-sectional view taken along the line BB of FIG.
Is a perspective view.

FIG. 12 is a perspective view showing a reference example of the present invention.

FIG. 13 shows an example of a conventional direct injection diesel engine, FIG. A being a sectional view and FIG. B being a plan view.

FIG. 14 is a schematic configuration diagram of an experimental apparatus according to the present invention.

FIG. 15 is a diagram showing a spray state for explaining the problems of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piston, 1a ... Outer peripheral wall, 1b ... Combustion chamber, 1c ... Intermediate wall, 5 ... Cylinder head, 6 ... Fuel injection valve, 7 ... Nozzle, 11 ... Mesh member 11a, 11b ... Fixing flange, 12 ... Fixing Plates 13, 15 ... Fixing screws, 1
4… Fixing ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Shown 57-20528 (JP, U) Shown 62-14127 (JP, U) Shown flat 4-127837 (JP, U)

Claims (4)

[Claims] 1. A fuel injection valve provided in a cylinder head, and a plurality of injection holes formed in a nozzle of the fuel injection valve,
A combustion chamber formed to have a depression at the top of the piston; a plurality of intermediate walls that are erected on the combustion chamber so as to surround the nozzle between the outer peripheral wall of the combustion chamber and the injection holes; A combustion chamber of a direct injection type diesel engine, comprising: a mesh member provided between the intermediate walls, wherein the spray injected from the injection hole collides with the mesh member. 2. A fuel injection valve provided in a cylinder head, a plurality of injection holes formed in a nozzle of the fuel injection valve,
A piston is provided with a combustion chamber formed to have a recessed portion in the upper portion, and a cylindrical mesh member fixed on the combustion chamber so as to surround the nozzle between the outer peripheral wall of the combustion chamber and the injection hole. A combustion chamber of a direct injection type diesel engine, wherein the spray injected from the injection hole is made to collide with the mesh member. 3. A fuel injection valve provided in a cylinder head, a plurality of injection holes formed in a nozzle of the fuel injection valve,
A piston, and a box-shaped mesh member fixed on the combustion chamber so as to surround the nozzle between the outer peripheral wall of the combustion chamber and the injection hole. A combustion chamber of a direct injection type diesel engine, wherein the spray injected from the injection hole is made to collide with the mesh member. 4. A horizontal mesh member is fixed to the upper surface of the piston, as claimed in any one of claims 1 to 3.
A combustion chamber of a direct injection diesel engine according to any one of 1.