JPH08165978A - Laser ignition method - Google Patents

Abstract

PURPOSE: To perform easy ignition combustion of fuel even ay laser of low output by method wherein a nozzle for washing is placed in a position different from that of a fuel injection nozzle in a cylinder and fuel is sprayed against an optical window through a nozzle for washing right after the start of the compression stroke of an engine. CONSTITUTION: When a solenoid valve 10 is opened at a bottom dead center position of a piston 15, fuel is injected as spray 13 for washing against the end face 12 of an optical window glass 3 through a nozzle 11 for washing to wash the optical window glass. Further, main fuel is injected as spray 7 through a main fuel nozzle 6 and in synchronism with the operation, irradiation with laser beams 1 is effected through the optical window glass 3 and fuel is ignited. In this case, the piston 15 is raised at a compression stroke and right before injection of main fuel, spray for ignition is injected through the nozzle 11 for washing in the vicinity of a top dead center at a pressure lower than that during washing of a window. Since spray for ignition has a high grain size and also high density, ignition is facilitated even by laser of a low output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser lighting method for a liquid fuel engine.

[0002]

2. Description of the Related Art A conventional laser ignition device will be described with reference to FIGS. FIG. 4 is a detailed view of a tip of a laser light guide portion of a conventional example, and FIG. 5 is an overall configuration diagram of a laser ignition device of a conventional example. In the figure, 5 is a combustion chamber, 6 is a main fuel nozzle, 1
Reference numeral 5 denotes a piston, which is a known element of an internal combustion engine. 1
Is a laser beam, and 4 is a laser beam guide, and has a hole through which the laser beam passes. An optical window glass 3 is provided at the end of the laser light guide 4 on the combustion chamber side and is transparent and separates the combustion chamber 5 from the outside air. A lens 2 is provided in the laser light guide 4. A main fuel spray 7 is injected from the main fuel nozzle 6 in synchronization with the crank angle. Reference numeral 1 denotes a laser beam for pulsed ignition which is emitted from a laser source (not shown) in synchronization with fuel into the combustion chamber 5 through an optical window glass 3.

The nozzle of the cleaning nozzle 11 is provided toward the end face 12 of the optical window glass 3 on the side of the combustion chamber of the optical window glass. The cleaning nozzle is connected to the solenoid valve 10 and further connected to the solenoid valve. The cleaning pump 9 and the fuel tank 8 are connected. The cleaning spray 13 is sprayed from the cleaning nozzle 11 toward the end surface 12 of the optical window glass in synchronization with the bottom dead center of the piston 15. The bottom dead center signal 14 of the piston 15 is input to the solenoid valve 10.

The bottom dead center signal of the piston 15 is input, the solenoid valve 10 is opened, the cleaning pump 9 sucks out the fuel in the fuel tank 8, and passes through the solenoid valve 10 to form the cleaning spray 11 from the cleaning nozzle 11. It is sprayed on the end face 12 of the optical window glass 3 and washed. The main fuel nozzle 6 injects the main fuel as a spray 7 in synchronization with the crank angle, and in synchronism with this, a pulsed laser beam 1 emitted from a laser source (not shown) passes through a laser light guide 4 and a lens. The laser beam 1 is focused on the laser beam 2, passes through the optical window glass 3, and is irradiated with the laser beam 1 from the end surface 12 of the window glass.

[0005]

However, fuel ignition by laser light utilizes the fact that a fuel having a high energy density causes dielectric breakdown of the fuel and high temperature plasma is generated to burn the surrounding fuel. As the fuel vaporizes and becomes finer and the density becomes smaller, dielectric breakdown is less likely to occur and the ignitability deteriorates. Therefore, it is necessary to increase the output of laser light.

An object of the present invention is to provide a laser ignition method which can easily and surely ignite a main fuel by using a low-power laser beam.

[0007]

According to the laser ignition method of the present invention, a fuel injection nozzle is arranged in a cylinder of an internal combustion engine, and a laser beam incident on a main fuel spray injected from the fuel injection nozzle through an optical window is injected. In the case of igniting via a cleaning nozzle, a cleaning nozzle is arranged at another position in the cylinder, and the same liquid as fuel is sprayed from the cleaning nozzle to the optical window immediately after the start of the compression stroke of the engine. Immediately before the fuel injection, lower the injection pressure than when cleaning the window, inject again so that the same liquid as the fuel does not arrive at the window, irradiate this fuel spray with laser light to ignite it, and set the flame As a result, the main fuel spray injected from the main fuel injection nozzle is then ignited.

[0008]

With the above-mentioned structure, the same liquid spray 1 as the fuel injected at high pressure from the cleaning nozzle 11 at the beginning of the compression stroke 1
3 reaches the window glass 3 of the optical window and cleans it.
Next, at the end of the compression stroke, the same liquid is again injected from the cleaning nozzle 11 immediately before the fuel injection. The jetting at this time does not reach the window glass because the jetting pressure is lower than that of the liquid jetted first.

Since this liquid ignition spray 13 'has a small injection pressure and a large particle size and a high density, plasma is easily generated when irradiated with laser light, and ignition combustion is easy even with a low-power laser. To do. Since the main fuel spray 7 injected immediately after that using this flame as a pilot flame easily ignites and burns, misfire can be prevented even if a low-power laser is used.

[0010]

EXAMPLES Examples of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram of the embodiment, FIG. 2 is a detailed view of a laser light guide tip portion of the embodiment, and FIG. 3 is an injection pressure diagram of a cleaning liquid. At the beginning of the compression stroke, a cleaning spray 13 of the same liquid as the fuel injected at high pressure from the cleaning nozzle 11 reaches the window glass 3 of the optical window and cleans the glass. Next, the piston 15 rises during the compression stroke, and immediately before the main fuel injection near the top dead center, the ignition spray 13 'is injected at a pressure lower than that at the time of window cleaning as instructed by the controller 14. Therefore, this spray 13 '
Does not reach the window glass.

At this time, the laser beam 1 is applied to the ignition spray 13 'with a timing and a focus. As a result, the ignition spray 13 'is ignited and burned. Spray 1 at this time
Since 3'is a low-pressure jet, the particles are large and can be easily ignited and burned by a low-power laser. Immediately after this, the main fuel spray 7 is injected from the main fuel nozzle 6 in synchronization with the crank angle, and the spray 1
Easily ignites the flame 16 generated by 3'as a pilot fire,
Burn. The pump 9'and the solenoid valve 10 'are for forming spray for ignition, and are operated by the controller 14 to perform the low-pressure injection as described above.

[0012]

Since the ignition spray 13 'jetted at a low pressure is irradiated with laser light, the spray particles are large and the density thereof is high.
Ignites and burns. Further, by injecting the main fuel nozzle into the flame burned at this time, the main fuel can be ignited by using this flame as a seed flame, so that the ignition efficiency is improved as compared with the conventional example in which the main fuel is directly irradiated with laser light.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram according to an embodiment of the present invention,

[Fig. 2] Same as above, detail drawing of the tip of laser light guide section,

FIG. 3 is a diagram showing an injection pressure of a cleaning liquid,

FIG. 4 is a conventional example shown in FIG.

FIG. 5 is a diagram corresponding to FIG. 1 of a conventional example.

[Explanation of symbols]

1 ... Laser light, 2 ... Lens, 3 ... Optical window glass, 4 ... Laser light guide, 5 ... Combustion chamber, 6 ... Main fuel nozzle, 7 ... Main fuel spray, 8 ... Fuel tank, 9, 9 '... Pump, 10,
10 '... Solenoid valve, 11 ... Washing nozzle, 12 ... Window glass end face, 13 ... Washing spray, 13' ... Ignition spray, 14 ...
Controller, 15 ... Piston, 16 ... Flame generated by ignition spray.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyasu Inagai 5-717-1 Fukahori-cho, Nagasaki City Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute

Claims (1)

[Claims] 1. A fuel injection nozzle is arranged in a cylinder of an internal combustion engine, and a main fuel spray injected from the fuel injection nozzle is ignited via a laser beam incident through an optical window. The cleaning nozzle is arranged at the position of, and the same liquid as the fuel is sprayed from the cleaning nozzle to the optical window immediately after the start of the compression stroke of the engine, and further injected immediately before the fuel injection from the cleaning nozzle from the window cleaning. The pressure is reduced, and the same liquid as the fuel is injected again so that it does not reach the window, this fuel spray is irradiated with laser light to ignite, and the flame is used as a pilot flame and is then injected from the main fuel injection nozzle. A laser ignition method comprising igniting a fuel spray.