JP2003247437A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine more friendly to the environment by suppressing production of NOx and particulate matters. <P>SOLUTION: In an internal combustion engine wherein combustion is caused by supplying into a combustion chamber a main fuel and water contributing to a power generation, the water is injected before, simultaneously or after the start of the main fuel injection per one time, and the water is re-injected before, simultaneously with or after the completion of the main fuel injection. The water injection at the beginning of the fuel injection makes combustion temperature decrease by making the thermal capacity of a pre-mixed gas inside the combustion chamber increase so that the production of NOx at the beginning of the combustion can be suppressed. Further, the water injection at the latter part of the fuel injection makes the fuel spray in combustion diffuse by the power of the water, and the production of the particulate matters can be suppressed by enhancing the mixture with air inside the combustion chamber. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for suppressing generation of nitrogen oxides and dust in an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art Nitrogen oxides (hereinafter referred to as NOx) are used in diesel engines used as power sources for power generation and ships.
As an effective technique for reducing NOx, a technique has been proposed that suppresses the generation of NOx by injecting fuel and water from the fuel injection valve into the combustion chamber and keeping the combustion temperature in the combustion chamber low.

As such a fuel / water injection diesel engine, for example, there is a technique described in Japanese Patent No. 2772114. FIG. 6 shows an example of a technique for reducing NOx as described above. In the figure, reference numeral 101 is a fuel tank,
102 is a fuel supply pump, 103 is a fuel injection pump, 1
Reference numeral 04 is a fuel solenoid valve, 105 is a water tank, 106 is a water supply pump, 107 is a fuel injection valve, and 108 is a fuel injection valve 1.
A water solenoid valve for connecting and disconnecting the water supply to 07, and a control device 109 for controlling the operation of the fuel solenoid valve 104 and the water solenoid valve 108.

A method of operating each part in the fuel / water injection diesel engine having the above-described structure will be described. Initially, the fuel solenoid valve 104 is opened, and the fuel in the fuel tank 101 is stored in the fuel supply pump 102 and the fuel injection pump 103.
It is sucked into the fuel injection pump 103 by the lowering operation of the plunger 112 inside. On the other hand, the water in the water tank 105 is pressure-fed to the fuel injection valve 107 by the water supply pump 106, but is not supplied to the fuel injection valve 107 because the electromagnetic valve 108 for water is closed. .

When the water solenoid valve 108 is opened during a period in which fuel is being sucked into the fuel injection pump 103, the supply pressure of the water supply pump 106 exceeds the internal pressure of the fuel passage 116, so that the water passage 123. Water in the fuel passage 116 pushes back the fuel on the fuel injection pump 103 side of the confluence portion 125 with the water passage 123 in the fuel passage 116,
Inflow to 6. Since the spring body for urging the needle valve 119 is given a stronger urging force than the force acting on the needle valve 119 by the supply pressure of the water supply pump 106, the needle valve 119 remains closed and the injection hole is closed. No water flows toward 120.

The fuel pushed back is supplied to the fuel injection pump 10
3 and flows back into the plunger chamber 111 by opening the fuel check valve 114. When the electromagnetic valve 108 for water is closed after a predetermined time has elapsed, the inflow of water into the fuel passage 116 is stopped.

As a result, in the fuel injection valve 107, fuel is filled in the oil sump portion 117 and the oil sump portion 117 to the confluence portion 125, and the fuel passage 1 upstream from the confluence portion 125.
16 is filled with a predetermined amount of water, and the upstream side thereof is filled with fuel again.
In 16 there will be as if there were layers in the order of "fuel / water / fuel".

When the solenoid valve 104 for fuel is closed in synchronization with the upward movement of the plunger 112, the plunger 1
Due to the ascending operation of 12, the internal pressure of the plunger chamber 111 increases, the fuel discharge valve 113 opens, and the pressurized fuel is discharged from the plunger chamber 111 and supplied to the fuel injection valve 107.

When the pressurized fuel is supplied to the fuel injection valve 107, the internal pressure of the fuel passage 116 and the oil sump 117 increases to the same level as the plunger chamber 111. As a result, the needle valve 119 opens and fuel is injected from the injection hole 120 toward the combustion chamber of the diesel engine. From the injection hole 120, first, the fuel filled in the oil sump portion 117 and the oil sump portion 117 to the confluence portion 125 is injected. This fuel starts burning after the ignition delay period.

Next, a predetermined amount of water filled upstream from the merging portion 125 is injected toward the flame of the previously injected fuel. This water jet becomes a mist to take in the air in the combustion chamber, generate an action of supplying air to the fuel injected earlier, activate the combustion, and at the same time suppress the temperature rise of the flame.

Finally, the fuel, which is filled to the upstream side of the predetermined amount of water, is injected. This fuel is injected into the atomized water that was previously injected, and actively burns while suppressing the temperature rise of the flame.

After a predetermined time has elapsed, the fuel solenoid valve 104
Is opened, the internal pressure of the plunger chamber 111 decreases, the needle valve 119 closes, and the injection ends. Shortly thereafter, the plunger 112 starts to descend, and the fuel supply pump 102 and the lowering operation of the plunger 112 cause the fuel tank 101 to move.
Fuel is drawn into the plunger chamber 111 from. In the fuel / water injection diesel engine of the present embodiment, the fuel / water injection into the combustion chamber is intermittently performed by repeating the above process.

[0013]

In the conventional fuel / water injection diesel engine as described above, the fuel injected prior to the water is burned by itself in each fuel injection, and the heat capacity due to the water is increased. Since it is not affected by the increase, NO
The generation of x cannot be suppressed. Further, the fuel injected subsequently to the water is taken into the combustion gas, and the introduction of air from the surroundings tends to be delayed, so that dust is easily generated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a more environmentally friendly internal combustion engine by suppressing the generation of NOx and the generation of dust.

[0015]

As a means for solving the above problems, an internal combustion engine having the following configuration is adopted. That is, the internal combustion engine according to claim 1 of the present invention is
In the first half of the fuel injection process, before, at the same time as, or after the start of injection of the main fuel that mainly contributes to the generation of power,
A heat capacity increasing fluid that mixes with the main fuel to increase the heat capacity of the fuel spray is injected.

According to another aspect of the present invention, in the internal combustion engine of the second aspect, the fuel spray of the main fuel is diffused in the latter stage of the fuel injection stroke, before, at the same time as, or after the end of injection of the main fuel mainly contributing to the generation of power. It is characterized by injecting a mixing promoting fluid that promotes mixing with air.

In the internal combustion engine according to a third aspect of the present invention, in the first half of the fuel injection stroke, the fuel spray is mixed with the main fuel before, at the same time as or after the start of injection of the main fuel mainly contributing to the generation of power. A heat capacity increasing fluid that increases the heat capacity of the main fuel is injected, and the fuel spray of the main fuel is diffused and mixed with air in the latter stage of the fuel injection process, before, at the same time as, or after the end of injection of the main fuel. A mixing promoting fluid for urging is injected.

In the present invention, in the first half of the fuel injection stroke, the heat capacity increasing fluid that mixes with the main fuel and increases the heat capacity of the premixture is injected before, at the same time as, or after the start of injection of the main fuel. This lowers the combustion temperature in the combustion chamber. This suppresses the generation of NOx in the early stage of combustion. It should be noted that a plurality of heat capacity increasing fluids having different compositions may be adopted and they may be injected simultaneously or separately. It is also possible to employ a plurality of compositions having the same composition but different state quantities such as temperature and pressure, and injecting them simultaneously or separately.

In the present invention, in the latter half of the fuel injection stroke, the mixing promoting fluid is injected before, at the same time as, or after the end of injection of the main fuel to diffuse the fuel in the combustion chamber and promote mixing with the air. This improves the burnout of the fuel. This suppresses the generation of soot and dust. It is also possible to employ a plurality of mixing promoting fluids having different compositions and to inject them simultaneously or separately. It is also possible to employ a plurality of compositions having the same composition but different state quantities such as temperature and pressure, and injecting them simultaneously or separately.

According to another aspect of the present invention, an internal combustion engine includes a fuel injection valve for injecting a main fuel that mainly contributes to generation of power into a combustion chamber, and before or simultaneously with the start of injection of the main fuel in the first half of the fuel injection stroke. Alternatively, the heat capacity-increasing fluid that mixes with the main fuel to increase the heat capacity of the fuel spray is injected, and in the latter stage of the fuel injection process, before, at the same time as, or after the end of injection of the main fuel. And a fluid injection valve for injecting a mixing promoting fluid that diffuses the fuel spray of the main fuel and promotes mixing with the air.

In the present invention, the structure of the internal combustion engine is simplified by injecting the heat capacity increasing fluid in the first half of the fuel injection stroke and the mixing promoting fluid in the latter half of the fuel injection stroke with one fluid injection valve. As a result, safe and reliable operation becomes possible, and the cost can be reduced by reducing the number of parts.

According to a fifth aspect of the present invention, an internal combustion engine has a fuel injection valve for injecting a main fuel that mainly contributes to generation of power to a combustion chamber, and before or at the same time as the start of injection of the main fuel in the first half of the fuel injection stroke. Alternatively, a first fluid injection valve that injects a heat capacity-increasing fluid that mixes with the main fuel to increase the heat capacity of the fuel spray, and a later stage of the fuel injection stroke than an end of injection of the main fuel. Alternatively, at the same time or later, a second fluid injection valve for injecting a mixing promoting fluid for diffusing the fuel spray of the main fuel and promoting mixing with air is provided.

In the present invention, the fuel injection valve, the first,
By separately providing the second fluid injection valve, the fuel,
Since the heat capacity increasing fluid and the mixing promoting fluid are separately injected from the dedicated injection valves, the control of the individual injection valves is simplified and safe and reliable operation is possible.

According to a sixth aspect of the present invention, in the internal combustion engine according to the fifth aspect, the injection direction of the first fluid injection valve is substantially opposite to the injection direction of the fuel injection valve.

In the present invention, by making the injection direction of the heat capacity increasing fluid face the injection direction of the fuel, the combustion of the fuel precedes, and the spray of the heat capacity increasing fluid is sprayed on the ignited fuel, so that water is generated. It does not hinder the ignition of fuel. Further, the injected heat capacity-increasing fluid hits the ignited fuel, and particles of the heat capacity-increasing fluid and particles of the fuel are mixed and the heat capacity of the entire fuel spray including water is increased, so that the fuel efficiency is improved. .

The internal combustion engine according to claim 7 is the internal combustion engine according to claim 5 or 6, characterized in that the injection direction of the second fluid injection valve is substantially equal to the injection direction of the fuel injection valve. .

In the present invention, by making the injection direction of the mixing promoting fluid equal to the injection direction of the fuel, the heat capacity increasing fluid is blown into the center of the fuel spray where combustion does not easily proceed,
Since the central fuel is pushed out of the spray, mixing with air is promoted and combustion efficiency is increased.

The internal combustion engine according to claim 8 is the internal combustion engine according to any one of claims 1 to 7, characterized in that water is used as one or both of the heat capacity increasing fluid and the mixing promoting fluid. To do.

In the present invention, water has a large heat capacity and a strong effect of lowering the combustion temperature, and water itself has the characteristic that it does not generate harmful products even when heat is applied. When used as an increasing fluid or a mixing promoting fluid, the effect of suppressing the generation of NOx and dust is enhanced. Further, since water is inexpensive and easily available, the operating cost of the internal combustion engine can be suppressed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an internal combustion engine according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a fuel / water injection diesel engine. In the figure, reference numeral 1 is a fuel tank, 2 is a fuel supply pump, 3 is a fuel injection pump, 4 is a fuel solenoid valve, 5 is a fuel injection valve,
6 is a water tank, 7 is a water supply pump, 7a is a relief valve,
Reference numeral 8 is a pressure accumulator, 9 is a solenoid valve for water, and 10 is a water injection valve.
The fuel injection valve 5 and the two water injection valves 10 and 10 sandwich a combustion chamber in a cylinder S of a diesel engine and form a piston head P.
Are located opposite to.

The fuel injection pump 3 has a plunger chamber 12 connected to the fuel tank 1 through a fuel supply pipe 11 and a cam C which is interlocked with a crankshaft of a diesel engine (not shown).
And a plunger 13 that reciprocates vertically to pressurize the fuel in the plunger chamber 12.

The solenoid valve 4 for fuel is of a normally open type which is normally opened and closed by energization. The operation of the fuel solenoid valve 4 is controlled by the control device 14.

The fuel injection valve 5 has a fuel passage 16 connected to the fuel injection pump 3 through a high-pressure fuel supply pipe 15, an oil reservoir 17 provided at the tip of the fuel passage 16, and a nozzle tip 18. A needle valve 19 which is reciprocally movable and arranged so that the needle tip faces the oil sump portion 17; a nozzle hole 20 provided at the tip of the nozzle tip 18; and a spring 21 for setting the opening pressure of the needle valve 19. Is equipped with.

The water solenoid valve 9 is of a normal close type which is normally closed and opened by energization.
The operation of this solenoid valve 9 for water is also controlled by the control device 14 like the solenoid valve 4 for fuel.

The water injection valve 10 serves as both the first fluid injection valve and the second fluid injection valve according to the present invention.
Water passage 23 connected to the pressure accumulator 8 via the water supply pipe 22
And a water reservoir 24 provided at the tip of the fuel passage 23 and a nozzle tip 25 that can reciprocate and the needle tip is the water reservoir 2.
4, the needle valve 26 arranged so as to face 4 and the nozzle tip 2
An injection hole 27 provided at the tip of the needle valve 5 and a spring 28 for setting the opening pressure of the needle valve 26 are provided.

In order to effectively diffuse and burn the fuel in the combustion chamber, the fuel injection from the fuel injection valve 5 is performed in the direction of injection together with the shape of the top surface of the piston P that defines the combustion chamber. It is very strictly regulated. The injection direction of the water injection valve 10 is configured to be substantially the same as the injection direction of the fuel injection valve 5 (see FIG. 2).

The operation of each part in the fuel / water injection diesel engine having the above-described structure will be described. Initially, the solenoid valve 4 for fuel is opened and the solenoid valve 9 for water is closed, and the fuel in the fuel tank 1 is stored in the fuel supply pump 2 and the plunger 1.
The lowering operation of 3 sucks into the plunger chamber 12. When the fuel intake to the fuel injection pump 3 progresses, the plunger 13 finishes the descending operation and starts to rise.

On the other hand, the water in the water tank 6 is pumped by the water supply pump 7 toward the pressure accumulator 8. When the inside of the pressure accumulator 8 reaches a predetermined pressure, the relief valve 7a opens and excess water is returned to the water tank 5. The internal pressure of the pressure accumulator 8 is set higher than the opening pressure of the water injection valve 10 (needle valve 26) by the relief valve 7a.

When the plunger 13 starts to rise, the fuel solenoid valve 4 is closed at an appropriate time, and the fuel pressurized by the ascending operation of the plunger 13 is supplied to the fuel injection valve 5, and the fuel passage 16 and the oil sump portion. The internal pressure of 17 rises to the same level as the plunger chamber 12. And the plunger 1
When the internal pressure of the oil sump portion 17 increases due to the further raising operation of 3, and the opening pressure of the needle valve 19 is exceeded, the needle valve 19 opens and fuel is injected from the injection hole 20 toward the combustion chamber.

At this time, the electromagnetic valve 9 for water is opened slightly prior to the start of fuel injection from the fuel injection valve 5, and the high-pressure water introduced into the pressure accumulator 8 is supplied to the water injection valve 10.
When high-pressure water is supplied to the water injection valve 10, the needle valve 26 opens and water is injected from the injection hole 27 into the combustion chamber. The first water injection is performed overlapping with the fuel injection from the fuel injection valve 5 in the first half of the fuel injection period, and ends when the water solenoid valve 9 is once closed.

Even after the first water injection is completed, fuel injection is continued. When the rising operation of the plunger 13 approaches the end and the internal pressure of the oil sump portion 17 falls below the opening pressure of the needle valve 19, the needle valve 19 closes and the fuel injection from the injection hole 20 ends.

At this time, the water solenoid valve 9 is opened again slightly before the end of the fuel injection, and the high-pressure water introduced into the pressure accumulator 8 is discharged from the injection hole 27 of the water injection valve 10 into the combustion chamber. Is jetted. The second water injection is overlapped with the fuel injection from the fuel injection valve 5 in the latter half of the fuel injection period, and is ended by closing the solenoid valve 9 for water after the fuel injection is completed. The change over time in the injection amount of fuel and water per unit time is shown in FIG. 3, and two fluids are simultaneously injected during the period in which fuel injection and water injection overlap.

FIG. 4A shows the state of the inside of the combustion chamber when the fuel is injected following the first water injection. The fuel is injected so as to follow the water that was previously injected, and is also supplied in the form of mist to the water that is drifting in the form of mist, so that the heat capacity of the fuel spray is increased by the amount of water.

FIG. 4B shows the state of the inside of the combustion chamber when the water is injected for the second time. The fuel spray floating in a mist in the combustion chamber burns rapidly on the outside, which is easy to come into contact with air.
Combustion in the latter part of the injection stroke concentrates in the center of the spray, and it is difficult to contact the air, so combustion does not proceed. Therefore, the fuel collected at the center of the spray is pushed outward by the second water, so that the burning after the fuel spray is improved.

In the above fuel / water injection diesel engine, when water is injected into the combustion chamber slightly prior to the start of fuel injection, fuel is sprayed into the combustion chamber where air and atomized water exist. Therefore, the heat capacity of the fuel supplied into the combustion chamber increases by the amount of water, and the combustion temperature decreases. This suppresses the generation of NOx in the early stage of combustion.

When water is injected into the combustion chamber slightly prior to the end of fuel injection, the atomized fuel in the combustion chamber is diffused by the force of the water, promoting mixing with the air in the combustion chamber and Burnout improves. This suppresses the generation of soot and dust.

In the present embodiment, the first water injection is performed before the fuel injection is started. However, as shown in FIG. 5A, the first water injection and the fuel injection are performed. Even if configured to start at the same time, FIG.
Even if the water injection for the second time is started slightly after the start of the fuel injection as shown in (4), the same effect as above can be obtained.

Further, in the present embodiment, the second water injection is configured to be performed before the end of the fuel injection. However, as shown in FIG. 5A, the second water injection is the end of the fuel injection. Even if configured to start at the same time, FIG.
Even if the second water injection is started slightly after the end of the fuel injection as shown in (b), the same effect as above can be obtained.

Further, in the present embodiment, the second water injection is configured to continue slightly after the fuel injection is finished, but the second water injection and the fuel injection may be finished at the same time. The same effect as above can be obtained.

In the present embodiment, the fuel injection valve 5 and the water injection valve 10 are provided separately, and the respective roles are shared. However, as in the conventional fuel / water injection diesel engine shown in FIG. "Fuel / water / water" using the fuel injection valve of
Even if the layered injection is performed in this order, the same effect as above can be obtained.

In the present embodiment, the first and second water injections are configured to be injected in the same direction, that is, in the direction substantially equal to the fuel injection direction. However, the water injection direction is set to the fuel injection direction. You may make it face each other.

In order to make the injection directions different between the first water injection and the second water injection, the water injection valve 10 used for the first time is used.
And the water injection valve 10 used for the second time are separately provided, and the water supply system (the water tank 6, the water supply pump 7, the pressure accumulator 8, and the electromagnetic valve 9 for water) to each water injection valve 10 is mainly provided. It is preferable to prepare two systems corresponding to each structure).

In this embodiment, the water injection is performed twice before and after the fuel injection, but the water injection is not divided into two times and the water injection is continuously performed while the fuel injection is performed. Even in this case, the same effect as the above can be obtained.

In the present embodiment, the temperature of water is not taken into consideration, but as described in, for example, Japanese Patent Laid-Open No. 2000-0106121, the water temperature of the second water injection is performed by exchanging heat with the exhaust gas. May be controlled to be higher than the temperature of the fuel (about 40 ° C. if the fuel is A heavy oil).

Even when the state quantities such as the water temperature and the pressure are made different between the first water injection and the second water injection, the water injection valve 10 used for the first time and the water injection valve used for the second time are used in the same manner as above. It is necessary to separately provide the water injection valve 10 that operates.

In this embodiment, the water injection is performed both in the first and second times. However, the first time is not limited to water, and the fluid having a larger heat capacity than the main fuel may be injected. The same effect as can be obtained. Specifically, it may be a combustible substance having a composition different from that of the main fuel, such as alcohol. By using such a combustible substance, it is possible to obtain a stronger power by increasing the thermal energy that is a source of power generation while lowering the combustion temperature. Further, even in the second time, not only water but also a fluid for diffusing the fuel in the combustion chamber, for example, exhaust gas or compressed air, can be injected to obtain the same effect as the above. In this case, it is necessary to prepare their supply system according to the type of each fluid.

[0057]

As described above, according to the internal combustion engine of the present invention, the fuel injection per injection is performed before, at the same time as, or after the start of injection of the main fuel, and mixed with the main fuel. By injecting the heat capacity-increasing fluid that increases the heat capacity of the premixed gas, the combustion temperature in the combustion chamber is lowered, so that the generation of NOx in the initial stage of combustion can be suppressed. As a result, it is possible to realize an internal combustion engine that has cleaner exhaust and is more environmentally friendly than ever before.

According to the internal combustion engine of the present invention,
By the fuel injection per time, before or at the same time as or after the end of the main fuel injection, by injecting a mixing promoting fluid that diffuses the fuel in the combustion chamber and promotes mixing with air,
Since the burnout of the fuel is improved, the generation of dust can be suppressed. This also makes it possible to realize an environment-friendly internal combustion engine with clean exhaust.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a fuel / water injection diesel engine as an embodiment according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a graph showing changes over time in the injection amounts of fuel and water.

FIG. 4 is a state explanatory view showing how to diffuse water and fuel injected into a combustion chamber.

FIG. 5 is a graph showing another pattern of changes over time in the injection amounts of fuel and water.

FIG. 6 is a diagram showing a configuration of a conventional fuel / water injection diesel engine.

[Explanation of symbols]

1 fuel tank 2 Fuel supply pump 3 Fuel injection pump 4 Solenoid valve for fuel 5 Fuel injection valve 6 water tank 7 Water supply pump 8 Accumulator 9 Solenoid valve for water 10 Water injection valve

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kuninori Ito             1-8 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa               Mitsubishi Heavy Industries Yokohama Research Center (72) Inventor Akihiro Yuki             1-8 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa               Mitsubishi Heavy Industries Yokohama Research Center (72) Inventor Akira Tsunoda             12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa Mitsubishi Heavy Industries             Yokohama Co., Ltd. (72) Inventor Takeshi Arai             12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa Mitsubishi Heavy Industries             Yokohama Co., Ltd. (72) Inventor Kouji Takasaki             6-1, Kasuga Park, Kasuga City, Fukuoka Prefecture F term (reference) 3G092 AA02 AB00 AB03 AB17 DE03S                       EA01 FA17 FA18 FA24

Claims (8)

[Claims] 1. A heat capacity increase for increasing the heat capacity of fuel spray by mixing with the main fuel before, at the same time as, or after the start of injection of the main fuel, which mainly contributes to generation of power, in the first half of the fuel injection stroke. An internal combustion engine characterized by injecting a fluid. 2. The fuel spray of the main fuel is diffused to promote the mixing with the air in the latter stage of the fuel injection process, before, at the same time as, or after the end of the injection of the main fuel mainly contributing to the generation of power. An internal combustion engine characterized by injecting a mixing promoting fluid. 3. The heat capacity increase for increasing the heat capacity of the fuel spray by mixing with the main fuel before, at the same time as, or after the start of injection of the main fuel that mainly contributes to the generation of power in the first half of the fuel injection stroke. A fluid is injected, and in the latter stage of the fuel injection process, a mixing promoting fluid that promotes mixing with the air by diffusing the fuel spray of the main fuel before, at the same time as, or after the end of injection of the main fuel is injected. An internal combustion engine characterized by: 4. A fuel injection valve for injecting a main fuel mainly contributing to generation of power into a combustion chamber, and a main fuel injection valve in the first half of a fuel injection stroke, before, at the same time as or after the start of injection of the main fuel. A heat capacity-increasing fluid that mixes with fuel to increase the heat capacity of the fuel spray is injected, and at the latter stage of the fuel injection stroke, before or at the same time as or after the end of injection of the main fuel, the fuel spray of the main fuel is injected. And a fluid injection valve for injecting a mixing promoting fluid that promotes mixing with air. 5. A fuel injection valve for injecting a main fuel mainly contributing to generation of power into a combustion chamber, and a main fuel injection valve before, at the same time as, or after the start of injection of the main fuel in the first half of the fuel injection stroke. A first fluid injection valve that injects a heat capacity-increasing fluid that mixes with fuel to increase the heat capacity of the fuel spray, and in the latter half of the fuel injection stroke, before, at the same time as, or after the end of injection of the main fuel, An internal combustion engine comprising: a second fluid injection valve that injects a mixing promoting fluid that diffuses the fuel spray of the main fuel to promote mixing with air. 6. The internal combustion engine according to claim 5, wherein the injection direction of the first fluid injection valve is substantially opposite to the injection direction of the fuel injection valve. 7. The internal combustion engine according to claim 5, wherein the injection direction of the second fluid injection valve is substantially equal to the injection direction of the fuel injection valve. 8. The internal combustion engine according to claim 1, wherein water is used as one or both of the heat capacity increasing fluid and the mixing promoting fluid.