JPS6329016A - Subchamber type diesel combustion chamber - Google Patents

Abstract

PURPOSE:To improve the mixing of air and fuel by forming a recessed part outside the opened port peripheral edge on the vortex subchamber side at the injection port for the communication between the vortex subchamber equipped with a fuel injection nozzle and a main chamber, thus generating a prescribed turbulent flow. CONSTITUTION:A vortex subchamber 2 is formed into a cylinder head 1, and an injection port 8 communicating to a cylinder chamber 4 is formed in inclination so that a swirl S is generated along the inner wall 2a, opened from one inner wall 2a side of the vortex subchamber 2 on the bottom part. Further, a passage 9 is formed in the upper part of the vortex subchamber 2, and a fuel injection nozzle 10 is installed into the passage 9. With such structure, a recessed part 11 is formed, positioned outside from the opened peripheral edge part 7b, at the part along the opened peripheral edge part 7b on the vortex subchamber 2 side at the injection port 8. Therefore, in the compression cycle and combustion cycle, a turbulent flow for improving the mixing of air and fuel is generated in the vortex subchamber 12 and a main chamber 6 by the recessed part 11.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pre-chamber type diesel combustion chamber, and particularly relates to a vortex flow 01
improves the mixture of air and fuel in the main room and eliminates NOx
, relates to a pre-chamber type diesel combustion chamber formed with a protrusion capable of generating turbulence that reduces smoke (exhaust particulates).

[Prior Art] In general, a sub-type diesel combustion chamber having a sub-chamber and a main chamber has a fuel efficiency of 140X, compared to a direct-injection diesel combustion chamber.
It is widely used in diesel passenger cars because it exhibits excellent combustion performance in terms of smoke, IC, and combustion noise. However, in recent years, there has been a demand for a drastic reduction in NOx and smoke (exhaust particulates), which are causes of pollution. In order to reduce these NOx and smoke, it is effective to improve the mixing of air and fuel.

As a proposal for promoting the mixing of air and fuel, a sub-seed diesel engine combustion structure f (described in Japanese Utility Model Application No. 51-27740) is known.

As shown in FIGS. 6 and 7, this proposal is to form a toroidal conical protrusion C located approximately in the center of the bottom of the hemispherical auxiliary chamber of cylinder a, and to direct the fuel to the conical protrusion C and swirl. An injection nozzle d that injects water toward the downstream side of S is arranged.

[Problems to be Solved by the Invention] The above proposal promotes evaporation and mixing of fuel by generating an air flow T in a toroidal direction around the conical protrusion 0, and thereby improves the air-fuel mixture generated. This was attempted to be combusted in the main chamber e.

However, although this air flow T seems to be effective in collecting air and steam near the bottom, it is effective in terms of stirring the vicinity of the nozzle, the upstream side of the swirl S, and the upper side of the subchamber. However, it is large. As mentioned above, there is a large amount of NOx.

Since the reduction of smoke lies in improving the mixing properties of fuel and air, it is considered that this point is still insufficient.

[Means for solving the problems] The present invention aims to solve the above problems,
The present invention constitutes a sub-chamber type diesel combustion chamber by forming a depression on the outside of the opening periphery on the swirl sub-chamber side of a nozzle that connects a swirl aI chamber equipped with an injection nozzle and a main chamber. .

[Function] During the compression stroke, compressed air is forced into the vortex subchamber through the nozzle. At this time, a large number of turbulent flows rotating around the axis of the swirl are generated by the depression formed at the peripheral edge of the nozzle. This turbulent flow flows from upstream to downstream in a swirl direction and stirs the air in the vortex subchamber. When combustion occurs in the vortex sub-chamber, the combustion gas is forced into the main chamber through the nozzle, but at this time too, strong turbulence is generated by the depression and sent to the main chamber, stirring the air in the main chamber. These create turbulence that increases air utilization when entering and exiting the nozzle.

[Embodiment] A preferred embodiment of the pre-chamber type diesel combustion chamber of the present invention will be described below with reference to the accompanying drawings.

1 shown in FIG. 1 is a cylinder head, 2 is a vortex tiJ chamber,
3 is the cylinder body, 4 is the cylinder chamber, 5 is the piston,
6 is a main chamber, and 10 is a fuel injection nozzle.

As shown in the figure, a spherical vortex sub-chamber 2 is formed in the cylinder head 1, and a nozzle 8 that opens from one inner wall 2a side of the vortex sub-chamber 2 and communicates with the cylinder chamber 4 is provided at the bottom of the cylinder head 1. The nozzle 8 is formed at an angle so as to generate a swirl S along the inner wall 2a of the vortex subchamber 2.

A cylindrical passage 9 is formed in the upper part of the vortex sub-chamber 2, and a fuel injection nozzle 10 is installed in this passage 9, facing the vortex sub-chamber 2.
are housed integrally. The fuel injection nozzle 10 is configured to inject fuel onto the inner wall 2a on the bottom side of the swirl sub-chamber 2 on the downstream side in the direction of the swirl S of the swirl sub-chamber 2.

Now, the feature of the subchamber type diesel combustion chamber of the present invention is that turbulent flow that improves mixing properties is distributed throughout the vortex subchamber 2 and the main chamber 6.

Therefore, in this embodiment, as shown in FIGS. 1 and 2, the portion where the flow velocity of the compressed air pushed in is maximum, that is, the portion along the opening periphery 7a of the jet nozzle 8 on the swirl subchamber 2 side. , a recessed portion 1 located outward from this and recessed as appropriate.
1 is formed. The recessed portion 11 has a shelf portion 15 extending in the radial direction of the nozzle 8 from the bottom of the swirl S sub-chamber 2 for generating the swirl S. They are formed so that they are on the same level, and the ridge lines formed by the recessed portions 11 are all formed to be corners. (Parts A, B, C, and D in FIG. 1) Next, the operation of this embodiment will be explained based on FIGS. 3 and 4.

During the compression process, the air compressed by the piston 5 passes through the nozzle 8 and is forced into the swirl subchamber 2 . At this time, a small turbulent flow T around the axis of the swirl is caused by the depression 11.
Many 1's occur. This turbulent flow T1 rides on the swirl S and is distributed throughout the vortex subchamber 2. When the fuel injection IF is injected from the fuel injection nozzle 10 in this state, the spray F is bent toward the inner wall 2a side under the influence of the swirl S, and is distributed in a widening manner toward the downstream side along the inner wall 2a. A jet n FM F + is generated. At this time, the generated turbulent flow T1 stirs the fuel spray B F 1 inside and outside, evaporates the fuel spray n FZ F 1 and promotes mixing with air.

As a result, an active air-fuel mixture with good ignitability is generated within the vortex DI chamber. The generation of an active mixture significantly shortens the ignition delay. When this active air-fuel mixture ignites, its flame spreads rapidly in the spray layer F1. Combustion of the spread flame is promoted by swirl S and turbulence T1. Here, since the volume of the vortex subchamber 2 is approximately 1/2 that of the main chamber 6, rich combustion can be achieved and HC can be reduced.

As shown in FIG. 4, as the piston 5 begins to descend and the pressure within the swirl M chamber 2 increases, the combustion gas and unburned air-fuel mixture within the swirl sub-chamber 2 are guided to the main chamber 6. At this time, the turbulent flow T2 is again created by the recessed portion 11, and this turbulent flow T2 is distributed throughout the main chamber 6 as shown in FIG.

As a result, it is mixed with fresh air in the main chamber 6, and the unburned fuel and soot (due to thermal decomposition) are re-combusted. Therefore, smoke (exhaust particulates),
Complete combustion is achieved with suppressed emissions of HC and NOx. Since combustion in the main chamber 6 is relatively slow, low noise can be achieved.

Incidentally, the recessed portion may be formed in the inner wall 2a of the swirl subchamber 2.

[Effects of the Invention] As is clear from the above explanation, the subchamber type diesel combustion chamber of the present invention can exhibit the following excellent effects.

Since a depression is formed outside the opening periphery on the side of the vortex sub-chamber of the nozzle that connects the vortex sub-chamber having the injection nozzle and the main chamber,
During the compression stroke and combustion stroke, turbulent flow can be generated in the main chamber to improve the mixing of air and fuel, thereby reducing NOx, HC.

Smoke and noise can be significantly reduced.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing a preferred embodiment of the pre-chamber type diesel combustion chamber of the present invention, Fig. 2 is a ■-■ line diagram of Fig. 1, and Figs. 3 and 4 show the combustion process. FIG. 5 is a top view of the piston, and FIGS. 6 and 7 are schematic diagrams showing conventional examples. In the figure, 2 is a vortex nl chamber, 7a is an opening periphery, 8 is a nozzle,
10 is a fuel injection nozzle, and 11 is a recessed portion. Figure 1 Figure 2 Figure 3 Figure 5

Claims (2)

[Claims] (1) An auxiliary chamber type diesel combustion chamber characterized in that a recess is formed outside the opening periphery on the side of the vortex auxiliary chamber of a nozzle that connects the vortex auxiliary chamber equipped with an injection nozzle and the main chamber. (2) The auxiliary chamber type diesel combustion chamber according to claim 1, wherein the injection nozzle is disposed so as to inject fuel to the bottom of the swirl auxiliary chamber on the downstream side in the swirl direction.