JP2646952B2 - Pre-combustion chamber diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-combustion chamber type diesel engine.

[0002]

2. Description of the Related Art In general, a pre-combustion chamber type diesel engine has a configuration in which a main combustion chamber and a pre-combustion chamber communicate with each other through an injection port, and a nozzle of a fuel injection valve is arranged in the pre-combustion chamber. Then, as this nozzle, a pintle nozzle 100 as shown in FIG. 5 was generally used in many cases. The pintle nozzle 100 has one nozzle hole 101, and the diameter of the nozzle hole 101 is usually about 1 to 1.5 mm. The rod-shaped valve body 102 is moved within the nozzle body 103 by the fuel supplied at 300 to 400 atm, and the nozzle hole 101 is opened and closed to inject the fuel into droplets having a diameter of about 50 μm. I have.

[0003]

The combustion of a diesel engine is fuel droplet combustion. Combustion starts when the fuel evaporates from the surface of the droplets in a high-temperature atmosphere and is properly mixed with air. This combustion is performed as shown in FIG.
_The excess air ratio where the generation of _x is large proceeds in the range of 1.0 to 1.1.

[0004] Combustion in a direct injection diesel engine is exactly the above-described droplet combustion, but combustion in a pre-combustion chamber diesel engine is slightly different. That is, a part of the fuel is burned in the pre-combustion chamber, and another part is gasified. Then, due to the pressure increase due to the combustion in the pre-combustion chamber, the air-fuel mixture in the pre-combustion chamber containing the unburned fuel is ejected from the injection port into the main combustion chamber,
It mixes with air in the main combustion chamber and burns. Fuel in the main combustion chamber is also that burns a droplet not only burning gaseous, it is difficult to burn in the lower range of the excess air ratio of NO _x generation.

In particular, in the above-mentioned conventional pre-combustion chamber type diesel engine, since the pintle nozzle is used as the fuel injection valve, the particle diameter of the fuel injected into the pre-combustion chamber is as large as about 50 μm as described above. The fuel could not be sufficiently gasified in the pre-combustion chamber. Therefore, the fuel has a high rate to be used in combustion enters the main combustion chamber from the injection port while the droplet, the combustion becomes more droplet combustion is NO _x generation rate proceeds in the range of high excess air ratio. For this reason, there was a problem that reduction of NO _x was insufficient.

According to the present invention, gasification of fuel is completed in a pre-combustion chamber, lean burn combustion is realized in a main combustion chamber, and NO
It is an object of the present invention to provide a pre-combustion chamber type diesel engine capable of significantly suppressing _x generation.

[0007]

According to the present invention, there is provided a pre-combustion chamber type diesel engine in which a nozzle of a fuel injection valve is disposed in a pre-combustion chamber 5 communicating with a main combustion chamber 1. Is a multi-hole nozzle 12 and the inner diameter of each nozzle is about 0.3 mm.
Heater wires 8 on the outer wall of the pre-combustion chamber 5 to heat
And a temperature measuring means (thermocouple 10) provided on the outer wall of the pre-combustion chamber 5 for measuring the wall surface temperature of the pre-combustion chamber 5, and the temperature measuring means (thermocouple 10). The energization of the heater wire 8 as the temperature holding means is switched ON / OFF in accordance with the temperature detected by the heater, so that the wall temperature of the pre-combustion chamber 5 becomes 300 ~
At 400 ° C., the nozzle 12 was inserted into the pre-combustion chamber 5.
The particle size of the fuel is from several μm to 3
It is characterized in that it is configured to inject at about 0 μm.

[0008]

The fuel injected from the multi-hole nozzle at a high pressure of about 1000 atm has a particle diameter of about several μm to 30 μm, and most of the particle diameter at the center becomes droplets of about several μm. The droplets instantaneously film boil and gasify upon contact with the wall surface of the pre-combustion chamber maintained at 300 to 400 ° C. by the temperature maintaining means. Fuel gasified partially burned and the remainder is combusted with a small lean-burn region NO _x generated is injected into the main combustion chamber from the injection port.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross section of a cylinder head 2 arranged above a main combustion chamber 1 of a diesel engine. A substantially cylindrical pre-combustion chamber 5 is provided in the cooling jackets 3 and 4 in the cylinder head 2. An injection port 6 facing the upper part of the main combustion chamber 1 is connected to the lower end of the pre-combustion chamber 5. A plurality of holes 7 are formed at the lower end of the injection port 6 so as to extend obliquely downward and outward, and are configured to guide the mixture in the pre-combustion chamber 5 into the main combustion chamber 1.

A heater wire 8 as a temperature holding means is wound around a part of the outer peripheral surface of the pre-combustion chamber 5 facing the cooling jackets 3 and 4 of the cylinder head 2.
The heater wire 8 is covered by an annular cover 9 and is fixed to the outer peripheral surface of the wall of the pre-combustion chamber 5. Heater wire 8
Is provided on the wall of the pre-combustion chamber 5 so as to reach the middle of the wall from the outer surface side.
0 is provided, and the temperature inside the pre-combustion chamber 5 can be estimated from the detected temperature. In the present embodiment, the O of the heater wire 8 is changed according to the temperature detected by the thermocouple 10.
By switching between N and OFF, the inner surface of the wall of the pre-combustion chamber 5 can be maintained at 300 to 400 ° C. by heating by the heater wire 8 and cooling by the cooling jackets 3 and 4.

A fuel injection valve 11 is provided at an open upper end of the pre-combustion chamber 5. The fuel injection valve 11 has a multi-hole nozzle 12 facing the upper end of the pre-combustion chamber 5, and a supply unit 13 for guiding fuel to the multi-hole nozzle 12.

As shown in FIG. 2, a sliding hole 16 for guiding a needle valve 15 described later is formed in the upper part of the main body 14 of the multi-hole nozzle 12. An oil reservoir 17 and an oil passage 18 are continuously formed in the sliding hole 16, and an end of the oil passage 18 formed in a tapered shape communicates with a suck hole 19. Main body 1 having a substantially hemispherical outer shape
A plurality of, for example, 4 to 8 nozzle holes 20 for communicating the sack hole 19 with the outside are formed at the tip of the nozzle 4.
The main body 14 has a vertical hole 21 for supplying fuel to the oil reservoir 17 from the fuel injection pump (not shown) via the supply unit 13. Next, the main body 14 is provided with a needle valve 15. That is, the sliding portion 15a of the needle valve 15 is guided by the sliding hole 16, and the distal end portion 1 formed integrally with the tip of the sliding portion 15a.
5b is provided in the oil passage 18 with a predetermined gap from the inner wall. The tip of the tip portion 15b is formed in a tapered shape, and the suck portion 19 can be shut off from the oil passage 18 by bringing the tip portion into close contact with the end of the oil passage 18.

In the above configuration, the fuel pressure-fed from a fuel injection pump (not shown) passes through the vertical hole 21 and reaches the oil reservoir 17, and the pressure causes the needle valve 15 to slide the sliding portion 15a through the sliding hole 16a. Guided to lift. At this time, fuel flows into the suck hole 19 through the oil passage 18 around the distal end portion 15b, and the fuel is injected outward from each nozzle hole 20. In the present embodiment, the inner diameter of the nozzle hole 20 is about 0.3 mm, and the fuel is supplied at a high pressure of, for example, about 1000 atm.
It becomes fine of about 30 μm.

During operation of the diesel engine having the pre-combustion chamber 5 and the fuel injection valve 11 configured as described above,
Fuel is supplied to the perforated nozzle 12 of the fuel injection valve 11 at a high pressure of about 1000 atm, which is higher than the conventional one. This fuel is sprayed into the pre-combustion chamber 5 from the plurality of nozzle holes 20 of the multi-hole nozzle 12 having an inner diameter smaller than the nozzle hole of the pintle nozzle. The particle diameter of the sprayed fuel particles has a level of several μm at the center.

At this time, the temperature of the wall of the pre-combustion chamber 5 is measured and monitored by the thermocouple 10, and according to the measurement result, the heater wire 8 is energized to heat the pre-combustion chamber 5, or The heating is stopped and the pre-combustion chamber 5 is cooled by the cooling water. By this control operation, the temperature of the inner surface of the wall of the pre-combustion chamber 5 is in the range of 300 to 400 ° C., more preferably 330 ° C.
380 ° C.

According to the knowledge of the present inventor, as shown in FIG. 3, the life of a light oil droplet when dropped on a high-temperature wall surface depends on the wall surface temperature. In the range from 300 to 400 ° C., more preferably in the range from 330 to 380 ° C., the life of the droplet in contact with the wall surface is extremely short and evaporates almost instantaneously.

Therefore, according to the present embodiment, the multi-hole nozzle 12
The fine fuel spray particles having a particle diameter of several μm injected from the pre-combustion chamber 5 heated and maintained at 330 to 380 ° C.
And instantaneously causes film boiling and gasification.
Some of the fuel burns, but most of the gasified fuel is injected into the main combustion chamber 1 through the hole 7 of the injection port 6 to perform lean burn gasification combustion. Thereby, the NO in the pre-combustion chamber 5
_{The x} level is greatly improved from the conventional 400 to 500 ppm to 100 ppm, which is equivalent to that of a gas engine.

[0018]

The pre-combustion chamber type diesel engine of the present invention
A multi-hole nozzle is used as the nozzle of the fuel injection valve facing the pre-combustion chamber, and the inner diameter of each nozzle is set to about 0.3 mm.
Fuel is injected into the pre-combustion chamber at a high pressure of about 000 atm to reduce the spray particle diameter to about several μm to 30 μm, and to reduce most of the particle diameter at the center to about several μm.
It is configured so that the spray particles are instantaneously gasified while being maintained at 00 to 400 ° C. Therefore, according to the present invention, the main combustion chamber a combustion of the lean-burn can be realized in, substantial NO _x reduction in gas engines parallel can be achieved even in a diesel engine.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention.

FIG. 2A is a sectional view of a multi-hole nozzle used in one embodiment of the present invention, and FIG. 2B is a partially enlarged view of FIG.

FIG. 3 is a graph showing the life of a droplet dropped on a high-temperature wall surface.

4 is a graph showing the propensity of such NO _x to air excess ratio.

FIG. 5A is a sectional view of a pintle nozzle used in a conventional pre-combustion chamber type diesel engine, and FIG. 5B is a partially enlarged view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main combustion chamber 5 Pre-combustion chamber 8 Heater wire as temperature holding means 11 Fuel injection valve 12 Perforated nozzle

Claims (1)

(57) [Claims] 1. A pre-combustion chamber diesel engine in the precombustion chamber communicating with the main combustion chamber and arranged nozzle of the fuel injection valve, each of said nozzle with the nozzle and the porous nozzle
The inner diameter of the pre-combustion chamber is set to about 0.3 mm, and a temperature maintaining means composed of a heater wire is provided on the outer wall of the pre-combustion chamber to heat the wall surface of the pre-combustion chamber. The temperature measurement means is provided on the outer wall of the pre-combustion chamber, and the power supply to the heater wire as the temperature holding means is switched ON / OFF in accordance with the temperature detected by the temperature measurement means, so that the heating by the heater wire and the cooling jacket The wall temperature of the pre-combustion chamber is reduced to 300 to 400 ° by cooling.
Coercive blood C, 1000 the gas from the nozzle to the pre-combustion chamber
At high pressure, the particle size of the fuel is set to several μm to 30 μm.
A pre-combustion chamber type diesel engine characterized by having a configuration in which injection is performed .