JP2004251194A - Gas engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas engine capable of sufficiently reducing NOx in an auxiliary combustion chamber. <P>SOLUTION: This gas engine is provided with a main combustion chamber 16 formed in a cylinder 13 to obtain a driving output by burning the lean gas supplied from the outside, the auxiliary combustion chamber 18 communicated with the main combustion chamber 16 to ignite with the combustion gas of the pilot fuel P, and a water injection means 24 for injecting water to the auxiliary combustion chamber 18. When igniting with the pressure of the injection of the pilot fuel P, water is injected by the water injection means 24 to maintain the strong ignition while lowering the combustion temperature of the auxiliary combustion chamber 18. As a result, NOx to be generated by a rise of the combustion temperature can be sufficiently reduced in the auxiliary combustion chamber 18. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas engine adopting a method of igniting by injecting pilot fuel into a sub-combustion chamber.
[0002]
[Prior art]
Conventionally, an engine forms a main combustion chamber that enables driving of a piston by combining a cylinder and a cylinder head, and a small-volume sub-combustion chamber is provided in the cylinder head so as to communicate with the main combustion chamber through a communication hole. In addition, there is another type in which a pilot oil valve for injecting pilot fuel is disposed in the auxiliary combustion chamber. When a drive output is obtained from such an engine, pilot fuel is supplied to the sub-combustion chamber from a pilot oil valve, compressed and self-ignited, and the combustion gas in the sub-combustion chamber is spread to the main combustion chamber, thereby achieving main combustion. The driving output is obtained via the piston and the like by burning the fuel gas in the room.
[0003]
However, since such an engine burns a lean air-fuel mixture, if a strong ignition is not provided, there is a problem that a combustion variation occurs, a high-concentration portion of fuel is formed, and NOx is generated. . In addition, there is a problem that energy heat efficiency is low.
[0004]
For this reason, in order to obtain high engine thermal efficiency while maintaining low NOx in recent engines, as shown in FIG. 2, a small volume auxiliary cylinder is connected to the main combustion chamber 4 through the communication hole 5. Some include a combustion chamber 6. Here, in the figure, 1 is a cylinder, 3 is a piston, 7 is a pilot oil valve arranged in a sub-combustion chamber 6, 8 is an intake port for supplying a lean gas of fuel, and 9 is an exhaust gas in the main combustion chamber 4. An exhaust port 10 for exhausting the air, an intake valve 10, and an exhaust valve 11. Here, a gas engine provided with the sub-combustion chamber 6 is disclosed in, for example, the following Patent Document 1.
[0005]
[Patent Document 1]
JP-A-11-324805
[Problems to be solved by the invention]
However, in recent years, exhaust gas regulations have become strict as a measure against environmental pollution, and even if the fuel is ignited by injection of the pilot fuel P in the sub-combustion chamber 6 as described above, the fuel may not remain in the sub-combustion chamber 6 during combustion. Since NOx increases due to a partial high temperature portion and an increase in combustion temperature, there has been a problem that reduction of NOx is not sufficient in the sub-combustion chamber.
[0007]
The present invention has been made in view of the above circumstances, and has as its object to provide a gas engine that can sufficiently reduce NOx in a sub-combustion chamber.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, a main combustion chamber formed in a cylinder to obtain a drive output by burning a lean gas supplied from the outside, and ignited by a combustion gas of pilot fuel in communication with the main combustion chamber. And a water injection unit capable of spraying water into the sub-combustion chamber.
[0009]
The second aspect of the present invention relates to the gas engine according to the first aspect, wherein the water injection means is a water injection valve.
[0010]
According to the first and second aspects of the present invention, since the sub-combustion chamber is provided with the water injection means, when the pilot fuel is ignited by the pressure, the water is injected by the water injection means to achieve strong ignition. At the same time, the combustion temperature in the sub-combustion chamber is lowered, and as a result, NOx generated by the increase in the combustion temperature can be sufficiently reduced in the sub-combustion chamber.
[0011]
When the water injection means is a water injection valve, an accurate amount of water can be sprayed and the timing of spraying can be adjusted, so that the combustion temperature of the sub-combustion chamber is suitably lowered, and NOx is further reduced. can do.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 shows an embodiment of a gas engine according to the present invention.
[0014]
In the gas engine of the present embodiment, the cylinder 13 and the cylinder head 14 are combined to form a main combustion chamber 16 that allows the piston 15 to be driven, and the cylinder head 14 is connected to the main combustion chamber 16 via a communication hole 17. A small-volume sub-combustion chamber 18 is provided in the main combustion chamber 16. An intake port 20 for supplying a lean gas of fuel through an intake valve 19 and an exhaust port for exhausting exhaust gas through an exhaust valve 21 are provided in the main combustion chamber 16. 22 is connected. The cylinder head 14 is provided with a starting spark plug (not shown) for igniting fuel in the main combustion chamber 16 when the engine is cold.
[0015]
On the other hand, a pilot oil valve 23 for injecting pilot fuel P is disposed in the sub-combustion chamber 18, and a water injection valve 24 of water injection means is provided. The water injection valve 24 is interlocked with the movement of the intake valve 19. It is configured to spray a small amount of water at an appropriate timing. Here, the nozzle of the water injection valve 24 may be a throttle type having a throttle stroke for injecting a small amount of water, a hose type for injecting water by pushing up a needle valve, or other shapes. Further, the spray amount of water is adjusted so as to have an appropriate ratio with respect to the volume of the sub-combustion chamber 18, the concentration of the lean gas or the pilot fuel P flowing into the sub-combustion chamber 18, and the like. Of the present invention can be used.
[0016]
Hereinafter, the operation of the embodiment that implements the gas engine of the present invention will be described.
[0017]
When a drive output is obtained from the engine, a lean gas of fuel is supplied to the main combustion chamber 16 with the driving of the intake valve 19 of the intake port 20 to flow the lean gas into the sub-combustion chamber 18. By injecting low-concentration pilot fuel P from the pilot oil valve 23 into the combustion chamber 18, a strong ignition is caused by the pressure, and the ignition of the sub-combustion chamber 18 is extended to the main combustion chamber 16, whereby the main combustion chamber 16 The lean gas is burned to obtain a drive output via the piston 15 or the like.
[0018]
Here, when the low-concentration pilot fuel P is injected from the pilot oil valve 23 in the sub-combustion chamber 18, a small amount of water is injected from the water injection valve 24 of the water injection means to the sub-combustion chamber 18 at substantially the same time or at a slightly shifted timing. Water is directly sprayed to cause strong ignition in the sub-combustion chamber 18 and at the same time lower the combustion temperature in the sub-combustion chamber 18. Also, in the main combustion chamber 16, the combustion temperature in the main combustion chamber 16 is reduced as the combustion temperature in the sub combustion chamber 18 decreases.
[0019]
As described above, according to the present embodiment, the spraying of water by the water injection valve 24 of the water injection unit maintains strong ignition in the sub-combustion chamber 18 and at the same time lowers the combustion temperature of the sub-combustion chamber 18 to reduce the combustion temperature. NOx generated by the rise can be sufficiently reduced in the sub-combustion chamber 18. Further, the combustion temperature in the main combustion chamber 16 is also reduced with the decrease in the combustion temperature in the sub-combustion chamber 18, so that NOx can be reduced also in the main combustion chamber 16. When the sub-combustion chamber 18 is ignited with a pilot oil valve and a spark plug as in the conventional example, the NOx concentration becomes high and the ignition power is lower than the ignition by the pressure by the injection of the pilot fuel P. Becomes weak and cannot respond to water spray.
[0020]
Further, when the water injection means is the water injection valve 24, it is possible to spray an accurate amount of water and adjust the timing of spraying, so that the combustion temperature of the sub-combustion chamber 18 can be suitably lowered, and NOx can be further reduced. it can.
[0021]
Note that the gas engine of the present invention is not limited to only the above-described embodiment, and that the water injection means is not limited to the above-described embodiment, and various other modifications may be made without departing from the spirit of the present invention. Of course, changes can be made.
[0022]
【The invention's effect】
According to the gas engine of the present invention, since the sub-combustion chamber is provided with the water injection means, when igniting by pressure by the injection of pilot fuel, it is necessary to maintain strong ignition by spraying water with the water injection means. At the same time, the combustion temperature in the sub-combustion chamber is lowered, and as a result, an excellent effect that NOx generated by the increase in combustion temperature can be sufficiently reduced in the sub-combustion chamber can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a gas engine according to the present invention.
FIG. 2 is a schematic view showing a conventional gas engine.
[Explanation of symbols]
13 Cylinder 16 Main combustion chamber 18 Sub combustion chamber 24 Water injection valve (water injection means)
P pilot fuel

Claims (2)

A main combustion chamber formed in the cylinder to obtain a drive output by burning a lean gas supplied from the outside, a sub-combustion chamber communicating with the main combustion chamber and igniting by combustion gas of pilot fuel; A gas engine, comprising: water injection means capable of spraying water into a sub-combustion chamber. The gas engine according to claim 1, wherein the water injection means is a water injection valve.

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