JPH10196508A - Internal combustion engine and start of combustion control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly complete the combustion with a lean air fuel ratio, by forming an air-fuel mixture of high temperature and high pressure in a combustion chamber, and using a laser source outputting the laser beam of which the wavelength is an excitation band of amost OH gp or CH gp, as a combustion starting means for combusting the air-fuel mixture. SOLUTION: The air-fuel mixture which is premixed by jetting the fuel from an injector 10, is introduced to a cylinder 2, a piston 3 is risen, and the air-fuel mixture is compressed to obtain a high temperature and high pressure condition, and the fueld is decomposed into the molecules of low molecular weight, including OH gp and CH gp by cracking. The compression ratio on this occasion, is determined so that the temperature of the air-fuel mixture in the compression top dead center is adjusted to be lower than the self-ignition temperature, that is, the temperature free from the self-ignition. The laser beam of about 310nm of wavelength is irradiated from a laser source 11 into a combustion chamber 11 immediately after the compression dead point, for exciting the OH gp in the air-fuel mixture to generate a large amount of OH radical. Thereby the chain reaction of the combustion is immediately and simultaneously started on the multipoints for combusting the air-fuel mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine provided with means for starting combustion by laser light and a method for controlling the start of combustion.

[0002]

2. Description of the Related Art In a conventional ordinary gasoline internal combustion engine, intake air and fuel are premixed and introduced as necessary into a cylinder defined by a cylinder head and a piston, and compressed by upward movement of the piston. The fuel injection is completed sufficiently earlier than the ignition timing to form a high-temperature, high-pressure mixture in which the fuel and air are relatively homogeneously mixed at the ignition timing, and is ignited by spark ignition with a spark plug near the compression end. And
The combustion of the air-fuel mixture is completed by the propagation of the flame in the combustion chamber starting from the ignition, and the generation of pressure is controlled by the ignition timing.

[0003] Further, there has been proposed an apparatus in which fuel is directly injected into a cylinder near a compression end of a piston and spark ignition is performed by a spark plug.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 7-332141, etc., a high compression ratio in which fuel is premixed to form a homogeneous mixture and self-ignition combustion is performed at a compression end. A premixed self-ignition internal combustion engine has also been proposed. If it can be realized, even if the air-fuel ratio is lean, combustion is completed simultaneously by multipoint ignition, high fuel efficiency and very low NOx emission concentration (about 10 ppm). , High efficiency and low emission engine can be obtained.

[0005]

However, in the above-mentioned ordinary gasoline internal combustion engine, reduction of combustion temperature and lean air-fuel ratio combustion are effective to reduce NOx in exhaust gas. Because of the flame propagation combustion, there is a problem that the gas at the end remains unburned and the ignition stability decreases as the air-fuel ratio becomes lean.Therefore, when the fuel supply is premixed, the flammable lean limit of the air-fuel ratio is 22 to 25 is the limit.

[0006] In the case of spark ignition by directly injecting fuel into a cylinder, the lean limit of the air-fuel ratio can be increased to 40 to 50. However, since the air-fuel mixture distribution is not homogenous, there is a possibility that smoke is generated. There is a problem that there is.

Further, in the premixed self-ignition internal combustion engine, it is very difficult to control the ignition timing because of self-ignition, and it is impossible to control the ignition timing stably especially in a wide load range. There's a problem.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention can cause a chemical reaction to occur at a desired time to start combustion, and can smoothly complete combustion by starting combustion at multiple points even at a lean air-fuel ratio. It is an object of the present invention to provide an internal combustion engine capable of achieving low emission with high fuel efficiency and high efficiency, and a combustion start control method thereof.

[0009]

SUMMARY OF THE INVENTION An internal combustion engine of the present invention forms a high-temperature and high-pressure air-fuel mixture in a combustion chamber formed by a cylinder, a cylinder head and a piston, and burns the air-fuel mixture. The means is constituted by a laser source that outputs a laser beam having an excitation band having a wavelength substantially of an OH group or a CH group.

[0010] Hydrocarbons in the fuel are composed of a combination of a plurality of CH groups, and when the air-fuel mixture is adiabatically compressed to a high temperature and high pressure in the compression process, hydrocarbons having a high molecular weight and unsaturated hydrocarbons are thermally decomposed. So-called cracking occurs in which the fuel molecules are decomposed into molecules having a low molecular weight including OH groups and CH groups, and the fuel molecules decomposed in this way undergo a combustion reaction. In the combustion reaction, CnHm and O ₂ react to generate CO ₂ and H ₂ O and heat. In order to start this chain of combustion reaction, activation is usually performed in the form of heat by spark ignition or the like. Giving energy. By giving the activation energy in this way, a chain reaction is started several milliseconds later, and light emission of an OH group or a CH group is recognized at the beginning of the chain reaction. Therefore, it can be seen that the generation of OH radicals and CH radicals starts the chain of the combustion reaction. Therefore, it is understood that the chain of the combustion reaction can be started by generating these OH radicals and CH radicals by any means.

Thus, according to the present invention, the OH group or the CH group is irradiated with a laser beam having the wavelength of the excitation band to excite the OH group or the CH group, whereby the OH radical or C
H radicals are directly generated to cause a chain reaction, that is, combustion.

As described above, since OH radicals and CH radicals, which are combustion control factors, are excited by giving energy in the form of light energy instead of heat energy, activation energy can be supplied extremely efficiently. The light energy of the irradiated laser light is 10-20m
J is sufficient, and may be less than half of 40 mJ of the ignition energy by the conventional ignition plug. In addition, the chain of combustion reaction can be immediately started by directly generating OH radicals and CH radicals by laser light irradiation, and a large amount of OH radicals and CH radicals can be simultaneously generated in the entire laser light irradiation region. it can.

Therefore, according to the present invention, the combustion can be started steadily at a desired time, the isocapacity is improved and the efficiency is high, and the combustion is started at multiple points to smoothly burn even at a lean air-fuel ratio. Can be completed and the maximum flame temperature is reduced, so that an internal combustion engine with low fuel consumption, high efficiency and low emission can be achieved.

[0014] In the past, there has been proposed an apparatus which ignites by a laser source, which applies thermal energy in the same manner as an ignition plug.
The thermal energy of mJ is output, and the operation is the same as the conventional one, and does not exhibit the above operation.

Further, according to the method of controlling combustion start of an internal combustion engine of the present invention, an air-fuel mixture is introduced into a cylinder whose upper and lower parts are closed by a cylinder head and a vertically movable piston, and the air-fuel mixture is compressed by upward movement of the piston. Then, at or immediately after the compression top dead center, a laser beam of an excitation band having a wavelength of almost OH group or CH group is irradiated, and the air-fuel mixture introduced into the cylinder is evenly mixed, and a high temperature is generated in the compression stroke. The OH group and the CH group are surely generated throughout the air-fuel mixture by being cracked by the high-pressure state, and immediately irradiate the air-fuel mixture with laser light at the compression top dead center or immediately thereafter as described above. At the same time, a chain reaction of combustion is started at multiple points. For this reason, the isocapacity is improved and the efficiency is high, and the flame propagation distance is shortened due to the start of combustion at multiple points, so that combustion at a lean air-fuel ratio becomes possible and low NOx combustion becomes possible.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1A, 1 is an internal combustion engine using gasoline as fuel, 2 is its cylinder, 3 is a piston,
Reference numeral 4 denotes a cylinder head that covers the upper surface of the cylinder 1 and forms a combustion chamber 5 with the upper surface of the piston 3. Reference numeral 6 denotes an intake port formed in the cylinder head 4, and an intake valve 7 for opening and closing an opening 6a of the intake port 6 with respect to the combustion chamber 5.
Is provided. Reference numeral 8 denotes an exhaust port formed in the cylinder head 4. An exhaust valve 9 for opening and closing an opening 8a of the exhaust port 8 with respect to the combustion chamber 5 is provided.
Reference numeral 10 denotes an injector that supplies fuel through the intake port 6 toward the stem base of the intake valve 7. 11
Reference numeral denotes a laser source as a combustion start means, which is disposed on one side of the cylinder head 4 facing the combustion chamber 5, and on the upper wall surface forming the combustion chamber 5, laser light from the laser source 11 is applied inside the combustion chamber 5. A concave portion 12 for irradiating a wide area is formed. The laser source 11 outputs near-ultraviolet laser light having a wavelength of approximately 310 nm, and the laser light having this wavelength is, for example, a wavelength 6 from a He-Ne laser.
This can be realized by using a laser source that doubles the frequency of the 32.8 nm laser light and outputs the laser light.

FIG. 1B shows the openings 6 of these intake ports 6.
a, the opening 8 a of the exhaust port 8, the arrangement of the laser source 11, and the laser light irradiation area (shown by oblique lines).

The operation of the above configuration will be described. Before the intake valve 7 opens, a predetermined amount of fuel is injected from the injector 10 to perform premixing, and then the intake valve 7 opens in the intake stroke to mix the air-fuel mixture. The mixture is introduced into the cylinder 2 and is evenly mixed in the cylinder 2. Then, the intake valve 7 is closed, the piston 3 rises, and the mixture is compressed, so that the mixture becomes high temperature and high pressure, and cracking occurs. As a result, the fuel is decomposed into small molecular weight molecules containing OH groups and CH groups.
Note that the compression ratio at this time is such that the air-fuel mixture temperature at the compression top dead center (TDC) is smaller than the auto-ignition temperature by Δ as shown in FIG.
The temperature is set so as to be lower by T and not to self-ignite. Immediately after the compression top dead center (TDC), a laser beam having a wavelength of approximately 310 nm is emitted from the laser source 11 to the combustion chamber 5.
And the OH groups in the air-fuel mixture in the irradiation area are excited to generate OH radicals. That is, 310
The light having a wavelength of nm is the light in the excitation band of the OH group,
The group becomes an OH radical at a reaction rate of about 10 ^-9 sec by being provided with light energy of this wavelength. In addition, the light energy of the laser beam irradiated for this reaction is sufficient to be 10 to 20 mJ. Thus, a large amount of O
Immediately after the generation of H radicals, a chain reaction of combustion starts, and as shown in FIG. 2, the air-fuel mixture immediately reaches a temperature equal to or higher than the self-ignition temperature, and a chain reaction of combustion is started simultaneously at multiple points. For this reason, the isocapacity is improved and the efficiency is high, and the flame propagation distance is shortened due to the start of combustion at multiple points, enabling combustion at a lean air-fuel ratio. NOx combustion is realized.

In the above description, an example is shown in which OH radicals are generated by irradiating a laser beam of approximately 310 nm to excite OH groups. However, it is necessary to irradiate a laser beam of approximately 430 nm to excite CH groups. May be used to generate CH radicals.

In the above-described embodiment, the fuel is injected from the injector 10 before the intake valve 7 is opened to form a premixture in the intake port 6, and the mixture does not self-ignite at the compression top dead center. The example of the internal combustion engine in which the temperature is raised and the laser beam is irradiated at a desired time to start the combustion at multiple points has been shown, but the fuel is injected from the injector 10 during the intake stroke to cause the cylinder to fire. An air-fuel mixture may be formed in the fuel cell 2, and laser light may be emitted from the laser source 11 immediately after the compression top dead center for combustion. Further, the present invention can be applied to an internal combustion engine in which fuel is directly injected into the combustion chamber during the compression stroke.

[0022]

According to the internal combustion engine of the present invention, a high-temperature and high-pressure air-fuel mixture is formed in a combustion chamber formed by a cylinder, a cylinder head and a piston as described above, and the air-fuel mixture is burned. Since the combustion initiating means is constituted by a laser source that outputs a laser beam having a wavelength of an excitation band of an OH group or a CH group, the wavelength of the excitation band for the OH group or the CH group in a high-temperature and high-pressure mixture is determined. By irradiating the laser light of the above, OH radicals and CH radicals, which are combustion control factors, can be generated very quickly and efficiently with little energy, so that the chain of the combustion reaction can be immediately started, and And OH radicals and CH radicals can be generated at the same time over the entire laser beam irradiation area. The possible low maximum flame temperature with a flame propagation distance can complete the smooth combustion in a lean air-fuel ratio is shortened, thus it is possible to achieve low emissions with low fuel consumption and high efficiency.

According to the combustion start control method for an internal combustion engine of the present invention, the air-fuel mixture is introduced into a cylinder whose upper and lower parts are closed by a cylinder head and a vertically movable piston, and the air-fuel mixture is moved upward by the piston. The laser beam is irradiated with laser light having an excitation band of almost OH group or CH group immediately after or at the compression top dead center, so that the air-fuel mixture introduced into the cylinder is evenly mixed and the high temperature during the compression stroke. The OH group and the CH group are surely generated throughout the air-fuel mixture by being cracked by the high-pressure state, and immediately irradiate the air-fuel mixture with laser light at the compression top dead center or immediately thereafter as described above. At the same time, a chain reaction of combustion is started at multiple points, and the above-described effect is exhibited.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of an embodiment of an internal combustion engine of the present invention, (a) is a longitudinal sectional view, and (b) is a plan view of an arrangement configuration of a main part.

FIG. 2 is a characteristic diagram of crank angle and temperature in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Piston 4 Cylinder head 5 Combustion chamber 11 Laser source

Claims (2)

[Claims] In an internal combustion engine that forms a high-temperature and high-pressure air-fuel mixture in a combustion chamber formed by a cylinder, a cylinder head, and a piston and burns the air-fuel mixture, the combustion start means includes a OH-based or CH-based wavelength. An internal combustion engine comprising a laser source that outputs a laser beam of the excitation band. 2. An air-fuel mixture is introduced into a cylinder whose upper and lower parts are closed by a cylinder head and a vertically movable piston, and the air-fuel mixture is compressed by upward movement of the piston. A method for controlling combustion start of an internal combustion engine, which comprises irradiating a laser beam having an excitation band substantially of an OH group or a CH group.