JPH0768900B2 - Direct injection diesel engine - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a direct injection diesel engine for achieving simultaneous reduction of smoke and nitrogen oxides (NO _X).

[0002]

2. Description of the Related Art In a direct injection diesel engine,
Towards the reduction of smoke and NO _X exhaust gas recirculation method (EGR), water injection, the improvement various proposals combustion system have been made. Among them, EGR has problems of durability and reliability such as deterioration of fuel consumption, increase of smoke, corrosion of EGR device due to exhaust gas, or deterioration of function. Further, water injection has problems such as rust in the combustion chamber, oil dilution, and large water consumption.

From the viewpoint of the combustion system, in the case of low-pressure injection, which is widely used at present, after the spray is ignited in the vicinity of the nozzle, it progresses while being wrapped in a flame, and at this time, the spray is air. At the same time, it burns while energizing the burnt gas generated by itself, so a high temperature part and an oxygen deficient part are formed in the center of the spray, which becomes a cause of smoke generation,
It is said that entrainment of burnt gas acts as a negative factor. Therefore, in order to reduce smoke, it is necessary to mix fuel and air rapidly, and methods such as swirl and squish are used to improve the air utilization rate. Since the mixing speed also increases, there is a contradictory problem that the heat release rate in the early stage of combustion increases due to the increase in premixed combustion, leading to an increase in NO _X , which makes it difficult to reduce smoke and NO _X simultaneously. ing.

In order to solve the above problems, a system has been proposed in which a high pressure injection, a small injection hole diameter nozzle, a shallow dish combustion chamber and a low swirl are combined. This will be explained with reference to FIG.
31 is a piston, 32 is a piston ring, 33 is a cylinder liner, 34 is a gasket, 35 is a cylinder head,
Reference numeral 36 denotes a fuel injection valve having a nozzle 37, and a combustion chamber 39 is formed at the top of the piston 31. When the piston 31 rises and reaches the vicinity of the top dead center, the spray F of the fuel injected from the nozzle 37 ignites at once on the wall surface 40, and then the flame H expands toward the center of the combustion chamber 39.
The center remains as a non-combustible area until the end of injection. That is,
The spray F proceeds until it reaches the wall surface 40 while sufficiently entraining the fresh air A on the non-combustible region side near the center of the combustion chamber 39, and on the wall surface 40 side, the burned gas is introduced and the spray F collides with the wall surface 40. Follow the combustion path. In the case of high-pressure injection, even if the injection timing is significantly delayed, ignition will occur, so in combination with the injection timing delay, it is possible to reduce smoke and NO _X simultaneously as compared with low-pressure injection.

[0005]

However, since the high-pressure injection has larger spray energy than the low-pressure injection, the flame H is suppressed from spreading toward the center of the combustion chamber 39 due to the injection energy. Therefore, since the spray F always introduces the fresh air A on the nozzle 37 side, the smoke is greatly reduced, but since the amount of air introduced until ignition is large and the amount of burned gas entrainment is small, as described above, all at once on the wall surface. Nothing happens if you ignite and compare at the same injection timing.
There is a problem that the amount of _X generated increases.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a direct injection diesel engine capable of reducing smoke and NO _x simultaneously and significantly.

[0007]

To this end, the direct injection diesel engine of the present invention has a main injection nozzle 5a for injecting fuel into the cylinder 1 and a secondary injection nozzle for injecting exhaust gas components into the vicinity of the main injection nozzle 5a. A direct injection diesel engine that has an injection nozzle 6a and injects the components of the exhaust gas before and after the start of fuel injection and in the latter stage of combustion, and includes a gas supply member 21 fixed to a lower surface recessed portion 3a of a cylinder head 3. The gas supply member 21 includes the sub injection nozzle 6a.
Is fitted, a through hole 24 through which the main injection nozzle 5a penetrates, an annular passage 25 formed on the outer periphery of the through hole 24, and the annular passage 25 and the dish portion 24 are communicated with each other. It is characterized in that it comprises a communicating passage 26 and a plurality of gas ejection holes 27 formed at the bottom of the annular passage 25.

It is also possible to have a sub-injection nozzle for injecting the exhaust gas component and water, and inject water in the high load region from the sub injection nozzle and inject the exhaust gas component in the medium to low load region. It should be noted that the numbers added to the above configurations are for comparison with the drawings for easy understanding, and the configurations of the present invention are not limited thereby.

[0009]

In the present invention, EGR is performed before and after the start of fuel injection.
When the gas is injected, the EGR gas E becomes the main injection nozzle 5a.
EGR is injected into the nearby fuel spray F part and EGR along with fresh air.
Since the gas E is entrained in the fuel spray F, the premixed combustion is suppressed due to the decrease in oxygen concentration, and NO _X is decreased.
When the EGR gas is injected in the latter stage of combustion, the EGR gas E is injected into the combustion flame portion, and the kinetic energy of the EGR gas further promotes the mixing of the fuel and air in the combustion chamber 4 and the combustion becomes active. Smoke left over is reduced,
Therefore, both before and after the start of fuel injection and in the latter stage of combustion, EG
By injecting R gas, it is possible to reduce both of the NO _X and smoke.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show one embodiment of a direct injection diesel engine of the present invention, FIG. 1 is a schematic configuration diagram, FIG. 2 shows the structure of the engine of FIG. 1, FIG. A is an enlarged sectional view, and FIG. FIG. 3 is a perspective view of the gas supply member, FIG. C is a plan view of the combustion chamber, and FIG. 3 is a diagram for explaining gas injection timing.

In FIG. 1, a diesel engine includes a cylinder block 1, a piston 2 and a cylinder head 3.
A combustion chamber 4 is formed on the top of the piston 2. The cylinder head 3 is provided with a main injection valve 5 for injecting light oil fuel and a sub injection valve 6 for injecting a part of exhaust gas (hereinafter referred to as EGR gas). Engine exhaust pipe 7
Is provided with an EGR valve 9, and components such as smoke are removed from the EGR gas by a trap filter 10. The EGR gas is pressurized by a pressure pump 11 and injected into the combustion chamber 4 from the auxiliary injection valve 6. Further, hydraulic oil is supplied to the sub injection valve 6 by a hydraulic oil pump 12 driven by an engine, and opening / closing of the sub injection valve 6 is controlled. Light oil fuel is supplied to the main injection valve 5 from the fuel pump 13 and injected into the combustion chamber 4. Signals of engine speed, engine load, and crank angle are input to the electronic control unit 15, arithmetic processing is performed based on these input signals, a valve opening signal is output to the EGR valve 9, and operation is performed. A gas injection timing signal is output to the oil pump 12.

In FIG. 2, a recess 3a is formed on the lower surface of the cylinder head 3, and the gas supply member 21 is fixed in the recess 3a with a screw 22. Gas supply member 21
Is a bottomed cylindrical dish 23 into which the sub-injection nozzle 6a of the sub-injection valve 6 is fitted, a through hole 24 through which the main injection nozzle 5a of the main injection valve 5 passes, and an outer periphery of the through-hole 24. And a communication passage 26 that connects the annular passage 25 and the dish portion 23, and a plurality of gas ejection holes 27 formed at the bottom of the annular passage 25. With this configuration, as shown in FIG. 2 (C), the fuel F is injected from the main injection nozzle 5a into the combustion chamber 4 from a plurality of injection holes, and the EGR gas E injected from the auxiliary injection nozzle 6a is the gas supply member. It is injected into the combustion chamber 4 through the dish portion 23 of 21, the communication passage 26, and the gas ejection hole 27.

The EG ejected from the gas ejection hole 27
The direction of the R gas E may be between the sprays F as shown in FIG. 2C, or may be the same as the direction of the sprays. Further, the number of injection ports of the main injection nozzle 5a and the number of gas ejection holes 27 are arbitrary.

The operation of the present invention having the above structure will be described. The electronic control unit 15 outputs a valve opening signal to the EGR valve 9 and a gas injection timing signal to the hydraulic oil pump 12 based on the crank angle signal, and as shown in FIG. EGR gas is injected into the combustion chamber 4 from the sub-injection nozzle 6a before and after the start and in the latter stage of combustion. When the EGR gas is injected before and after the start of fuel injection, the EGR gas E is injected into the fuel spray F portion near the main injection nozzle 5a, and the EGR gas E is entrained in the fuel spray F along with the fresh air, so that the oxygen concentration is reduced. As a result, premixed combustion is suppressed and NO _X is reduced. In the latter half of combustion, E
When the GR gas is injected, the EGR gas E is injected into the combustion flame portion, and the kinetic energy of the EGR gas further promotes the mixing of the fuel and the air in the combustion chamber 4 and the combustion becomes active and remains unburned. Smoke is reduced. Therefore, by injecting the EGR gas both before and after the start of fuel injection and in the latter stage of combustion, both NO _X and smoke can be reduced.

FIG. 4 shows the experimental results in the above embodiment. In the figure, the dotted line shows the case where CO ₂ which is one component of the exhaust gas is injected into the intake pipe (normal EGR), and the solid line shows the case where CO ₂ is injected from the sub-injection nozzle 6a in the present invention. According to this, C of 1% of the intake amount
A NO _x reduction rate of 60% is obtained with O ₂ injection.

In the above embodiment, before and after the start of fuel injection and in the latter stage of combustion, E is introduced from the auxiliary injection nozzle 6a into the combustion chamber 4.
Although the GR gas is injected, NO _X and smoke greatly change depending on the engine load and rotation speed. Therefore, if these are detected and the injection timing of EGR gas is determined, NO _X and smoke can be further reduced. It will be possible.
FIG. 5 shows another embodiment of the present invention. For high engine loads, when an attempt to reduce the NO _X by the injection of smoke level is high EGR gas, there is a problem that smoke is greatly increased. On the other hand, a technique is known in which NO _X is reduced by injecting water into the intake pipe to lower the combustion temperature in the cylinder. However, since water mixes with the entire intake air, water adheres to the wall of the cylinder liner, especially in the low and medium range. In the load range, there are problems such as rust, oil dilution, and increase in particulates, and it is not appropriate to adopt this technique. Therefore, in the present embodiment, as shown in FIG. 5, water is injected from the sub injection nozzle 6a in the high load region, EGR gas is injected in the medium to low load region, and NO _X is reduced in the entire load region. I am trying to let you. In the method of injecting water from the sub-injection nozzle 6a, water is injected into the combustion chamber in the vicinity of the main injection nozzle before and after fuel injection, so the water does not directly contact the cylinder liner, and the adverse effects such as rust and oil dilution are small. Further, since water is effectively introduced directly into the spray, the amount of water can be small, and therefore, adverse effects such as rust and oil dilution are small.

The present invention is not limited to the above embodiments, and various modifications can be made by those having ordinary knowledge in the technical field to which the present invention belongs. For example, in the above embodiment, a part of the exhaust gas is injected from the sub-injection nozzle 6a, but gases such as CO ₂ and N ₂ which are the components of the exhaust gas are prepared in the cylinder and this gas is used alone. You may make it inject with.

[0018]

As is apparent from the above description, according to the present invention, in the case of high-pressure injection, the EGR gas is directly injected into this incombustible region by utilizing the characteristic that the vicinity of the nozzle during fuel injection remains as an incombustible region. As a result, the following effects can be expected.

(A) Since the EGR gas can be injected into a required amount and a required place when needed, the effect of simultaneously reducing NO _X and smoke is great. That is, the conventional EG
External EGR that introduces R gas directly into the combustion chamber from the intake pipe
In the case of, since the EGR gas is mixed in the entire intake air, the EGR gas adheres to the cylinder liner wall, which adversely affects the wear of the piston ring and the cylinder liner, the oil deterioration, and the like. Since the injection is performed near the main injection nozzle before and after the injection is started or in the flame after the top dead center, the EGR gas does not directly contact the cylinder liner, and the adverse effects such as wear of the piston ring and the cylinder liner and oil deterioration are small. Further, since the EGR gas is effectively introduced directly into the fuel spray, the amount of the EGR gas is small, the influence on smoke deterioration is small, and the adverse effects such as wear and oil deterioration on the engine are small.

[0020] (ii) by injecting the EGR gas into the combustion chamber 4 from the secondary injection nozzle 6a at both of the fuel injection before and after the start and combustion late, it is possible to simultaneously and significantly reduce the smoke and NO _X.

[0021] (c) using the secondary injection nozzle, it is in the high load region by injecting water, if in injecting the EGR gas in the low load region, can be reduced both of the NO _X and smoke at full load region.
Further, unlike the intake pipe injection, the amount of water is small because the water is directly injected into the combustion chamber, and there are no problems such as rust, oil dilution, and increase in particulates. Further, soot and the like accumulated in the passage due to the EGR gas are automatically washed away by the water injection, so that the durability of the engine is improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a direct injection diesel engine of the present invention.

2 shows the structure of the engine of FIG. 1, FIG. A is an enlarged cross-sectional view, FIG. B is a perspective view of a gas supply member, and FIG. C is a plan view of a combustion chamber.

FIG. 3 is a diagram for explaining a gas injection timing in the present invention.

FIG. 4 is a diagram for explaining an experimental result in the present invention.

FIG. 5 is a diagram for explaining another embodiment of the present invention.

FIG. 6 shows an example of a conventional direct injection diesel engine,
FIG. A is a sectional view and FIG. B is a plan view.

[Explanation of symbols]

1 ... Cylinder, 2 ... Piston, 5a ... Main injection nozzle, 6
a ... Sub injection nozzle 21 ... Gas supply member, 23 ... Plate portion, 24 ... Through hole, 25
... annular passage 26 ... communication passage, 27 ... gas ejection holes, F ... fuel spray, E ...
EGR gas

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location F02B 23/06 M F02M 25/022 25/07 570 L 580 C F02M 25/02 T (72) Invention Masanori Komori 2530, Kuma, Tsukuba-shi, Ibaraki Japan Automobile Research Institute, Inc., Shin-Combustion System Research Co., Ltd. Stem Research Institute (56) Reference Japanese Unexamined Patent Publication No. 5-5467 (JP, A) Actually opened 62-101057 (JP, U) Actually opened 58-163634 (JP, U)

Claims (2)

[Claims] 1. A main injection nozzle for injecting fuel into a cylinder, and a sub-injection nozzle for injecting exhaust gas components in the vicinity of the main injection nozzle. The exhaust gas components before and after the start of fuel injection and in the latter stage of combustion. A direct injection diesel engine for injecting a gas, comprising: a gas supply member fixed to a recessed portion of a lower surface of a cylinder head, the gas supply member including a dish part to which a sub injection nozzle is fitted, and a main injection nozzle. Through hole, an annular passage formed on the outer periphery of the through hole, a communication passage communicating the annular passage and the dish portion, and a plurality of gas ejection holes formed at the bottom of the annular passage. A direct-injection diesel engine characterized by consisting of 2. A sub-injection nozzle for injecting exhaust gas components and water, wherein the sub-injection nozzle injects water in a high load region and injects an exhaust gas component in a medium to low load region. Item 1. A direct injection diesel engine according to Item 1.