JP3039155B2 - Fuel combustion promotion method for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel combustion promotion method of a diesel engine for pilot injection prior fuel amount in accordance with the operating state of the engine for injecting (main injection)
About the.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. 60-125754 discloses an injection of a fuel amount according to the operating state of an engine (main injection).
Prior to this, a fuel injection device for a diesel engine has been disclosed which aims to prevent a diesel knock or the like by realizing smooth combustion and gradual combustion by performing pilot injection prior to performing the pilot injection and reducing the combustion speed.

[0003]

However, even in the above-mentioned technology which aims to promote combustion by performing pilot injection and main injection, diffusion and atomization of pressurized fuel injected from a fuel injection nozzle are performed. However, the performance, accuracy and the like of the fuel injection nozzle are limited and cannot be said to be sufficient. For this reason, the concentration of the mixture of fuel and air varies, and as a result, there is a problem that combustion is incomplete and smoke is easily discharged.

Therefore, the present invention sufficiently premixes fuel and air by performing air injection after the pilot injection is performed and before the main injection is performed. Then, the fuel and air are sufficiently premixed to make the mixture concentration uniform,
Then, the main injection is performed to completely burn the combustion to reduce the amount of smoke emission.

[0005]

The present invention SUMMARY OF] is the fuel combustion promoting method of a diesel engine to promote the combustion of the fuel by performing the main injection and subsequent pilot injection in the same stroke, after the pilot injection is performed Air injection
Between the air and the fuel in the pilot injection.
Mix to form a premixed mixture, then perform the main injection
The premixed gas is burned together with the fuel in the main injection.
And wherein the Serco.

[0006]

[Action] for pressurized fuel by injecting pressurized air for the pilot injected pressurized fuel is diffused and atomized fuel and air that sufficiently Do the uniform premixed air-fuel mixture concentration. Also, the vaporization of the fuel spray for pilot injection is promoted.
And the ambient temperature around TDC decreases accordingly
Therefore, when the fuel in the main injection burns,
Temperature rise does not occur, and as a result, NOx generation is suppressed
Is done.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 2 shows a combustion chamber 1 to which the method for promoting fuel combustion of a diesel engine according to the present invention is applied. The combustion chamber 1 is formed by a recess at the top of a piston 2, a cylinder 3 and a cylinder head 4. Further, a fuel injection valve 5 for performing pilot injection and subsequent main injection toward the combustion chamber 1 and an air injection valve 6 for performing air injection are provided in the cylinder head 4. The fuel injection valve 5 is a single-hole injection valve having an injection port for directing the fuel injection direction to the center of the combustion chamber 1, and the air injection valve 6 has a nozzle at its tip for directing the air injection direction to the center of the combustion chamber 1, and This is a multi-hole injection valve having an injection port directed in the circumferential direction of the combustion chamber. Further, a donut-shaped collision plate 7 is attached to the air injection valve 6, and a hole formed at the center of the collision plate 7 is provided on the injection direction of the fuel injection valve 5 (toward the center of the combustion chamber 1). ing. The size and position of the impingement plate 7 and the hole formed in the center of the impingement plate 7 are such that the fuel injected from the fuel injector 5 through the hole is directed toward the center of the combustion chamber 1 and through the hole. The uninjected fuel is formed so as to be directed in the circumferential direction of the combustion chamber 1 by colliding around a hole provided at the center of the collision plate 7.

FIG. 3 is a schematic diagram of a fuel combustion promoting device for a diesel engine to which the method for promoting fuel combustion of a diesel engine according to the present invention is applied. The distribution type fuel injection pump 8 for supplying the fuel to the fuel injection valve 5 is operated in synchronization with the crankshaft 11 by the rotational driving force from the crankshaft 11 of the diesel engine 10, and pressurized fuel is supplied to the fuel injection valve 5. Supply. The distribution type fuel injection pump 8 is a fuel injection pump that performs a pilot injection prior to injecting a fuel amount (main injection) according to the operating state of the engine. And a subsequent main injection. In addition, the air injection pump 9
Similarly to the distribution type fuel injection pump 8, the diesel engine 10 operates in synchronization with the crankshaft 11 by the rotational driving force from the crankshaft 11 of the diesel engine 10. This air injection pump 9
Has the same structure as that of the distribution type fuel injection pump 8 except that air is pressure-fed, and supplies pressurized air to the air injection valve 6.

Next, the operation of this embodiment will be described with reference to FIGS.
It will be explained in. As shown in the flowchart of FIG. 1, first, in step 101, pilot injection is performed from the fuel injection valve 5 toward the combustion chamber 1. Next, step 10
At 2, air is injected from the air injection valve 6 toward the combustion chamber 1. Next, in step 103, the main injection is performed from the fuel injection valve 5 toward the combustion chamber 1. And step 1
At 04, air injection is performed again from the air injection valve 6 toward the combustion chamber 1. Next, the operation of the present embodiment will be described in more detail with reference to FIG. During the compression stroke of the diesel engine 10 A (while the piston 2 reaches the top dead center)
Then, pressurized fuel is injected from the fuel injection valve 5. (Pilot injection) At this time, a part of the pressurized fuel injected from the fuel injection valve 5 passes through the hole of the collision plate 7 attached to the air injection valve 6 and is directed toward the center of the combustion chamber 1. Pressurized fuel is collision plate 7
Collides with the periphery of the hole and points in the circumferential direction of the combustion chamber. When the pilot injection from the fuel injection valve 5 is completed, the pressurized air is supplied from the air injection valve 6 at a timing B during the compression stroke of the diesel engine 10 (a timing at which the piston 2 approaches the top dead center from the timing A during the compression stroke). It is injected. At this time, the pressurized air injected from the air injection valve 6 is directed from the plurality of injection ports toward the center of the combustion chamber 1 and the circumferential direction of the combustion chamber 1. By injecting pressurized air from the air injection valve 6 having a plurality of injection ports at the middle stage B of the compression stroke, the combustion chamber 1 is at the middle stage A of the compression stroke.
The pressurized fuel injected in the central and circumferential directions is diffused and atomized. As a result, the fuel and air are sufficiently premixed, and the concentration of the air-fuel mixture is made uniform. Next, when the compression stroke end time C of the diesel engine 10 comes (immediately before the piston 2 reaches the top dead center), pressurized fuel is injected again from the fuel injection valve 5. (Main injection) At this time, similarly to the pilot injection, a part of the pressurized fuel injected from the fuel injection valve 5 passes through a hole of the collision plate 7 attached to the air injection valve 6 and is directed toward the center of the combustion chamber 1. Oriented,
The other pressurized fuel collides around the hole of the collision plate 7 and is directed in the circumferential direction of the combustion chamber 1. At the time C of the end of the compression stroke of the diesel engine 10, the air-fuel mixture starts compression ignition and starts burning. The combustion at this time is pressurized by injecting pressurized air into the pilot-injected pressurized fuel, compared to a conventional diesel engine fuel injection device that only performs pilot injection and subsequent main injection. Since the fuel is diffused and atomized, the fuel, the empty fuel, and the air are sufficiently premixed to complete combustion. In the middle of the explosion stroke D of the diesel engine 10 (the piston 2 is in the process of reaching the bottom dead center, the latter stage of combustion), the compressed air is again injected from the air injection valve 6. At this time, similarly to the case where the compressed air is injected from the air injection valve 6 during the compression stroke halfway B, the compressed air injected from the air injection valve 6 is supplied from a plurality of nozzles toward the center of the combustion chamber 1 and the combustion chamber 1. Orient in the circumferential direction. By injecting pressurized air from the air injection valve 6 in the later stage of combustion, the air-fuel mixture in the combustion chamber 1 during combustion is disturbed. As a result, unburned components such as soot generated in the late stage of combustion in an oxygen-deficient state are oxidized to suppress emission of smoke. Further, even if a high-temperature portion is partially present in the air-fuel mixture during combustion in the combustion chamber 1, the high-temperature portion of the air-fuel mixture is diffused by injecting the pressurized air from the air injection valve 6. Thus, thermal NOx is suppressed. The pressurized fuel injected from the fuel injection valve 5 adheres to the partition wall of the combustion chamber 1 and the collision plate 7. By injecting pressurized air from the air injection valve 6, the adhered fuel is scattered, and thus the combustion is performed. It is possible to suppress the presence of a high temperature part in the partition wall of the chamber 1 and the collision plate 7, and it is possible to reduce thermal NOx and diesel knock. In this embodiment, the pilot injection and the subsequent main injection are performed by the distribution type fuel injection pump 8, but a fuel injection valve having the function of performing the pilot injection and the subsequent main injection may be used. In the present embodiment, the pressurized fuel injected from the fuel injection valve 5 has the configuration in which the collision plate 7 is provided. However, even if the configuration does not include the collision plate 7, the operation and effect of the present invention are exhibited. Of course it is. In this embodiment, the compressed air is injected from the air injection valve 6 after the pilot injection and the main injection are performed by the fuel injection valve 5, respectively. However, the compressed air is injected after the main injection is performed. It is needless to say that the operation and effect of the present invention can be exhibited even without doing so.

[0010]

According to the present invention, the pilot injection fuel and air are premixed and the main injection is carried out toward a mixture having a uniform concentration, so that the combustion of the mixture becomes complete combustion and the smoke is suppressed. Can be done. Further, even if the fuel injected from the fuel injection valve adheres to the combustion chamber partition, the adhered fuel can be scattered by performing air injection after the fuel injection. Not present, so that thermal NOx and diesel knock can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the operation of one embodiment of the present invention.

FIG. 2 is an embodiment of a combustion chamber to which an embodiment of the present invention is applied.

FIG. 3 is a schematic diagram of a fuel combustion promoting device to which an embodiment of the present invention is applied.

FIG. 4 is a diagram for explaining the operation of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Combustion chamber 2 ... Piston 3 ... Cylinder 4 ... Cylinder head 5 ... Fuel injection valve 6 ... Air injection valve 7 ... Impact plate 8 ... Distribution type fuel injection Pump 9 ・ ・ ・ Air injection pump 10 ・ ・ ・ Diesel engine 11 ・ ・ ・ Crankshaft

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 45/00 F02M 45/02 F02M 45/04 F02M 45/08 F02M 67/02 F02M 67/14 F02B 23/00 F02B 23 / 02 F02B 23/06

Claims (1)

(57) [Claims] In a fuel combustion promotion method for a diesel engine, in which pilot injection and subsequent main injection are performed during the same stroke to promote fuel combustion , air injection is performed after pilot injection is performed.
Premix by mixing air and fuel in pilot injection
Aiki is formed and then the main injection is performed to
Fuel combustion promotion method of the diesel engine, characterized that you combusting the fuel in the main injection a.