JP2000008898A - Pre-mixed-forced-ignition combustion method for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent self-ignition of fuel injected in advance to ensure combustion. SOLUTION: When a piston 2 starts rising from the position of -180 deg. (a bottom dead center), a 95% of fuel is injected from a main fuel injection nozzle 5 to form pre-mixture of the fuel and air 10, (A). At a time point where the piston rises to the position of -90 deg., water is injected from a water injection valve 6 for a predetermined period to cool the pre-mixture and to stir mixture. Accordingly, growth of nucleus that is subject to the self-ignition is prevented thereby to prevent the self-ignition (B). When the piston 2 rises to the position of 0 deg. (a top dead center) to compress the pre-mixture, a remaining 5% of the fuel is injected from a fuel injection valve 7 for an ignition so that a stabilized ignition source is formed and is ignited to perform lean pre-mixed combustion 13, (C). Accordingly, in a next (D), the pre-mixed combustion prevents smoke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a premixed forced-ignition combustion method for a diesel engine, which prevents uncontrolled combustion of premixed fuel by self-ignition and performs reliable combustion of a lean premixed gas. is there.

[0002]

2. Description of the Related Art FIG. 6 is a view showing the operation of a piston of a conventional diesel engine. In FIG. 6, (e) shows the position of the piston, showing the rotation angle of the crank, and the piston at each rotation angle. The process at the position of (a),
(B), (c), and (d). In (a), the piston 2 gradually starts rising from -180 ° (bottom dead center),
The air 30a starts to be compressed in the cylinder 1. In (b), the piston 2 gradually rises and compresses the air as in 30b, reaching the position of 90 °, and (c) compresses to 0 ° of top dead center, at which point the main fuel valve 5 From fuel 31a
Shows a state in which diffusion combustion 31b is performed, and (d) shows a state in which the piston moves down to a position of 90 °, depresses the piston, and rotates the crank. In this state, the mixture concentration and the gas temperature are reduced. A non-uniform area is generated, and the amount of air in the late stage of combustion becomes insufficient, and smoke 32 is generated in this area.

FIG. 7 is a view for explaining a state in which the above-mentioned smoke 32 is generated. A flame 40 is generated around the fuel 31a injected from the main fuel valve 5, and the fuel in the region 43 is thinned. caused the state of low temperature, as a result, NO _X generation area 41, the smoke generation region 42 occurs.

[0004] Method for premixed combustion using a premixed fuel of a mixture of air and fuel in advance in order to reduce the occurrence and _the amount of NO _X in the smoke, such as described above is realized, such premixing In the combustion method, self-ignition of the premixed fuel occurs before diffusion combustion occurs, and control of the combustion timing becomes impossible, preventing such self-ignition, performing reliable combustion, and , (D), smoke 22 is generated and the amount of generated NO _X increases, but it is desired to prevent this.

[0005]

As described above [0006] In the conventional diesel engines uneven concentration of the gas mixture and gas temperature is generated, the occurrence and _the amount of NO _X of smoke is increased, pre solve this problem A mixed combustion method is employed. However, in this premixed combustion system, self-ignition occurs, the combustion speed cannot be controlled, the control for reliably burning the lean premixed gas cannot be performed, and the fuel is fixed and fired,
It has been desired to make the combustion stable.

Therefore, in the present invention, the fuel is used as a lean premixing system, the timing of fuel injection is devised, and water is appropriately injected and mixed to prevent self-ignition and promote premixing. It is an object of the present invention to provide a premixed forced ignition combustion method for a diesel engine that can reliably perform combustion.

[0007]

The present invention provides the following methods (1) to (5) in order to solve the above-mentioned problems.

(1) Part of the fuel to be charged into the cylinder is injected into the cylinder from the suction step to the compression step and mixed with air to form a lean premixed gas. A premixed forced ignition combustion method for a diesel engine, characterized in that the fuel is injected into a cylinder as ignition fuel to cause diffusion combustion of the remaining fuel and premixed combustion of the lean premixed gas.

(2) In the above (1), a predetermined amount of water is injected into a cylinder during a compression step from the injection of fuel for forming the lean premixed gas to the ignition. Premixed forced ignition combustion method for diesel engines.

(3) The method for premixed forced ignition combustion of a diesel engine according to (2), wherein the water is injected from a water injection valve.

(4) In the above (1), a predetermined amount of water is injected into a cylinder when fuel for forming the lean premixed gas is supplied, wherein the premixing of the diesel engine is performed. Forced ignition combustion method.

(5) In the above (4), the water is injected by injecting the fuel and water in layers, injecting the fuel and water independently, or by converting the fuel and water into an emulsion state. A premixed forced ignition combustion method for a diesel engine, wherein the method is any of injection systems.

In (1) of the present invention, fuel is injected into the cylinder at an early stage to form a lean premixture, and the remaining fuel is injected as ignition fuel at the ignition timing and ignited. Therefore, a lean premixture is formed, the excess air ratio increases, the fuel has a uniform concentration, the gas temperature also becomes uniform, and N
Region O _X generating region and smoke is generated is eliminated, uniform combustion is made.

Further, in (2) of the present invention, water is injected in the process of forming a lean premix, and in (4) of the present invention, water is injected at the time of fuel injection to form a lean premix. Since water is injected, the cooling of water prevents the growth of ignition nuclei during the formation of a lean premixture, and the growth of the ignition nuclei is prevented by agitation of the ignition nuclei by the injection of water. Is prevented.

In (3) of the present invention, the water injection is performed by the water injection valve, so that the water injection system becomes a simple system. In (5), water and fuel are layered or water and fuel are separated. Since the water and the fuel are separately and simultaneously injected in separate systems or the water and the fuel are injected as an emulsion, the water and the fuel are uniformly mixed, so that the growth of the ignition nucleus can be effectively prevented.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a diagram illustrating the operation of a method for premixed forced ignition combustion of a diesel engine according to a first embodiment of the present invention. FIG. 1 (E) shows the positions of pistons as in the conventional example, and FIGS. FIG. 4 is a view showing each step of a piston. (A) shows that the piston 2 is 180 °
(Lower dead center) is a time point at which the air 10 starts to be compressed and the air 10 starts to be compressed. In this process, 95% of the fuel 11a is injected from the main fuel valve 5 into the cylinder 1 to mix with the air 10. Facilitate.

In FIG. 2B, the piston 2 rises to the position of -90.degree. To compress the premixed fuel and air, and at this time water is supplied from the water injection valve 6 to a predetermined position as will be described later with reference to FIG. This shows a state in which time injection is performed. In this step (B), the pre-mixed gas is a period in which self-ignition is likely to occur, injecting water, cooling with the heat capacity of the water, and stirring the ignition nucleus by the momentum of the water injection to grow the ignition nucleus. To prevent self-ignition. Although not shown, the water injection valve 6 is provided at a position where the main fuel valve 5 and the ignition fuel valve 7 do not interfere with each other.

In (C), the premixed gas, in which self-ignition has been prevented in (B), is compressed by the piston 2 and the piston 2
° (top dead center), at which point the remaining 5% of the fuel is injected from the ignition fuel valve 7 to form a stable ignition source. Thus, the premixed gas is ignited, and lean premixed combustion 13 is performed. Although the position of the ignition fuel valve 7 is not shown, it is provided at a position facing the main fuel valve 5.

(D) shows a state in which the piston 1 is pushed down by the lean premixed combustion 13 to a position of 90 °, and the premixed combustion is performed at perfect timing, so that the conventional smoke is generated. not, and also to reduce generation of NO _X.

FIG. 2 is a diagram showing the timing of water injection, that is, the timing of water injection in the first embodiment described with reference to FIG. In step (B), water is -9.
The water is injected from the water injection nozzle 6 in the range of 0 ° to 0 °, but is preferably sprayed in the form of a mist and injected so as to improve the mixing with fuel and air. By injecting water during such a period, the ignition nucleus is cooled so as not to grow, and the ignition nucleus is prevented from growing by stirring due to the momentum by the water injection. Thereby, self-ignition is prevented, and ignition is performed by the fuel from the ignition fuel valve 7 in the step (C).

FIG. 3 is a diagram showing the timing of water injection in the premixed forced ignition combustion method for a diesel engine according to the second embodiment of the present invention. Water injection is performed in the step (B) shown in FIG. You. The time of water injection is in the range of -150 ° to 120 ° at the position of the piston, and (a) is an example in which the water is injected in a stratified manner from the main fuel nozzle. That is, as shown, layers are formed like fuel 15a, water 16, and fuel 15b and injected.

FIG. 3 (b) shows that in the second embodiment, the fuel and water are supplied independently from two systems at the same -150 °
In this example, fuel is injected from the main fuel valve 5 and water is injected from the water injection valve 6 at a timing of 120 °.

FIG. 3C shows a second embodiment in which a fuel and water are mixed in advance and injected as an emulsion fuel 19. This emulsion fuel 19 is similarly at -150 ° to -120 °. The fuel is injected from the main fuel valve 5 in the range of °.

The amount of water described above includes the first and second water amounts.
In any of the embodiments, the maximum value of water is set to fuel / water = 1/1, or about 7/3 in a small example, and the amount of fuel does not change and the amount of water flowing into the cylinder 1 does not change. It increases.

FIG. 4 is a conceptual diagram showing an example of a main fuel valve according to the second embodiment described above. One main fuel valve injects fuel and water as shown in FIG. 3 in a layered state. Things. In FIG. 4A, reference numeral 20 denotes a main fuel valve, which has a plurality of injection nozzles 21 and is connected to a fuel pump 26 through a pipe 22 and a fuel system pipe 25. A water supply pipe 24 is connected in the middle of the fuel system pipe 26 from a water supply source 23 via an on-off valve 27.
Therefore, fuel and water can flow into the pipe 22 in layers.

FIG. 4 (b) shows the inside of the pipe 22, in which the water 16 is inserted in the middle of the fuel 15a by operating the on-off valve 27, so that the fuel 15a, the water 1
6. A stratified flow such as the fuel 15b can be formed, and the stratified jet fluid thus formed in the pipe 22 is jetted from the nozzle 21.

FIG. 5 is a graph showing the reduction of the NO _X amount between the diffusion combustion (Y) and the lean premixed combustion (X) in the conventional diesel engine. In the lean premixed combustion (X), the air amount is reduced. NO _X when becomes lean, the fuel is 95%
The amount is rapidly reduced, also, NO _X amount when the fuel is less air amount is large is reduced to the contrary. Therefore, when 95% fuel is initially injected and a lean premix is formed as in the first and second embodiments of the present invention, the NO _X amount is significantly reduced as compared with the conventional case.

In the first embodiment described above, 95% of the fuel is injected from the main fuel valve 5 in the step (A) of the piston 2 and then water is injected from the water injection valve 6 in the step (B). In the step (C), the remaining 5% of the fuel is injected from the pilot fuel valve 7. In the second embodiment, water is injected together with the 95% fuel in the step (A). In (C), since the remaining 5% of the fuel is injected from the pilot fuel valve 7, self-ignition is prevented by water injection, premixing is promoted, and generation of smoke due to uneven combustion is also prevented. Is done. The ratio between the main fuel and the ignition fuel is 95%.
% And 5%, but may be 90% and 10% or 85% and 15%.

[0029]

According to the premixed forced ignition combustion method for a diesel engine of the present invention, (1) a part of the fuel to be charged into the cylinder is injected into the cylinder from the suction step to the compression step and mixed with air. A lean premix is formed, and the remaining fuel is injected as ignition fuel into the cylinder at the time of ignition to perform diffusion combustion of the remaining fuel and premix combustion of the lean premix. And By such a method, a lean premixed gas is formed, the excess air ratio increases, the fuel has a uniform concentration, the gas temperature also becomes uniform, and there is no region where NO _X is generated or a region where smoke is generated. Combustion is made.

According to a second aspect of the present invention, in the above-mentioned first aspect, a predetermined amount of water is injected into the cylinder during a compression step from the injection of fuel for forming the lean premixed gas to the ignition. According to a fourth aspect of the present invention, in the first aspect, the water is injected by injecting a predetermined amount of water into the cylinder when fuel for forming the lean premix is injected. Features. By such a method, the growth of ignition nuclei during the formation of a lean premixture is prevented by cooling the water,
This is prevented by stirring the ignition nucleus by water injection, and self-ignition is prevented before the ignition point.

Further, (3) of the present invention is characterized in that, in the above (2), the water is injected from a water injection valve, and in the (5) of the present invention, in the above (4), The water injection is characterized by being one of a method of injecting fuel and water in layers, injecting fuel and water independently, or injecting fuel and water in an emulsion state. I have. By such a method, the growth of the ignition nucleus can be effectively prevented by uniformly mixing the water and the fuel.

[Brief description of the drawings]

FIGS. 1A, 1B, 1C, and 1D are diagrams illustrating the operation of a method for premixed forced ignition combustion of a diesel engine according to a first embodiment of the present invention; FIGS. (E) is a diagram showing the crank rotation angle and the position of the piston.

FIG. 2 is a diagram showing timing of water injection according to the first embodiment of the present invention.

FIGS. 3A and 3B are diagrams showing timing of water injection in a premixed forced ignition combustion method for a diesel engine according to a second embodiment of the present invention, wherein FIG. 3A shows a case where water and fuel are stratified, and FIG. If water and fuel are injected independently,
(C) shows the case where water and fuel are in an emulsion state, respectively.

4A and 4B show a configuration of a main fuel valve applied to a premixed forced ignition combustion method for a diesel engine according to a second embodiment of the present invention, wherein FIG. 4A is a configuration diagram, and FIG. FIG.

[5] a diagram showing the effect of the present invention, is a diagram showing the relationship between the air amount and the NO _X reduction in lean premixed.

FIG. 6 is a diagram illustrating the operation of a conventional diesel engine.
(A), (b), (c), (d) is a diagram showing each step of the piston, and (e) is a diagram showing the rotation angle of the crank and the position of the piston.

FIG. 7 is a diagram showing diffusion fuel in a main fuel valve of a conventional diesel engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Piston rod 5, 20 Main fuel valve 6 Water injection valve 7 Ignition fuel valve 10 Air 11a, 11b, 15a, 15b, 17 Fuel 12 Premixed air 13 Lean premixed combustion 14 Smoke 16, 18 Water 11a , 31a Fuel 21 Injection nozzle 22 Pipe 23 Water supply source 24 Water supply pipe 25 Fuel system pipe 25 Fuel pump

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tatsuo Takaishi 5-717-1, Fukahori-cho, Nagasaki-shi In Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Keisuke Sonoda 5-717-1, Fukahori-cho, Nagasaki-shi Mitsubishi (72) Inventor Noriyasu Inaga, 5-7-17-1 Fukabori-cho, Nagasaki-shi F-term (reference) in Nagaishi Engineering Co., Ltd. 3G066 AA07 AB02 AB08 AD08 BA14 BA24 BA25 DA04 DA09 3G092 AA02 AA09 AB15 AB17 BA08 BB13 BB20 DE02S DE03S FA17 FA18

Claims (5)

[Claims] 1. A part of fuel to be injected into a cylinder is injected into the cylinder from an intake step to a compression step and mixed with air to form a lean premixed gas, and the remaining fuel is supplied to the cylinder at an ignition timing. A diffusion combustion of the remaining fuel and a premixed combustion of the lean premixed gas by injecting the mixture as ignition fuel into the engine. 2. A diesel engine according to claim 1, wherein a predetermined amount of water is injected into the cylinder during a compression step from the injection of fuel for forming the lean premixed gas to the ignition. Premixed forced ignition combustion method. 3. The method for premixed forced ignition combustion of a diesel engine according to claim 2, wherein the water is injected from a water injection valve. 4. A premixed forced ignition combustion method for a diesel engine according to claim 1, wherein a predetermined amount of water is injected into the cylinder when fuel for forming the lean premixed gas is injected. 5. The method of injecting the water is performed by injecting fuel and water in layers, injecting fuel and water independently, or injecting fuel and water in an emulsion state. 5. The method for premixed forced ignition combustion of a diesel engine according to claim 4, wherein: