JP3930639B2 - Pre-combustion chamber type gas engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pre-combustion chamber type gas engine that is mainly useful as a drive source for stationary power generation equipment.
[0002]
[Prior art]
In recent years, lean combustion gas engines have attracted attention due to demand for low pollution. A conventional lean combustion gas engine has mainly used a pre-combustion chamber system using an ignition plug as an ignition source. Apart from this, an engine called a pilot injection gas engine (dual fuel engine) is also known. This engine is an engine having a structure in which a pilot oil (liquid) of about 5 to 15% of the total heat ratio is directly injected into a main combustion chamber, and gas fuel is combusted using this as an ignition source. This is realized by injecting a small amount of pilot fuel from a main fuel injection valve of a general diesel engine.
[0003]
[Problems to be solved by the invention]
By the way, since the conventional pre-combustion chamber type gas engine with a spark plug is combustion of a lean air-fuel mixture, if a strong ignition energy is not applied, a combustion fluctuation accompanied by misfire may occur. Further, compared with a diesel engine having the same cylinder diameter, NOx is as low as about 1/10, which is advantageous to the environment, but has a drawback of low engine thermal efficiency.
[0004]
With regard to improvement in combustion fluctuation, various studies have been conducted on optimization of the spark plug position in the pre-combustion chamber and uniformization of the mixed air in the pre-combustion chamber in order to ensure combustion in the pre-combustion chamber. However, since it does not contribute to an increase in ignition energy, there is a limit to improving engine thermal efficiency and combustion fluctuation.
[0005]
Further, the conventional pilot injection gas engine has a limitation in reducing NOx and dust, and has a drawback that it cannot take full advantage of the low emission pollution that is an advantage of the gas engine.
[0006]
In consideration of the above circumstances, the present invention can obtain a higher engine thermal efficiency while maintaining a low NOx, thereby making it possible to take advantage of the low pollution (low CO2) of the gas engine. The purpose is to provide.
[0007]
[Means for Solving the Problems]
A first aspect of the present invention is a gas engine that obtains a driving output by supplying gaseous fuel to a main combustion chamber defined by a piston, a cylinder, and a cylinder head and burning the gas fuel, and the cylinder head is mixed with the main combustion chamber. A pre-combustion chamber with a spark plug that serves as an ignition source for the gas and a pilot fuel injection valve that injects a pilot oil amount with a total heat ratio of 0.2 to 5% and serves as an ignition source for the air-fuel mixture in the main combustion chamber A pre-combustion chamber with a pilot fuel injection valve is provided.
[0008]
According to a second aspect of the present invention, in the first aspect, the pre-combustion chamber with the spark plug and the pre-combustion chamber with the pilot fuel injection valve function in the same combustion cycle at substantially the same time or slightly shifted from each other, so that As described above, the air-fuel mixture in the main combustion chamber is burned.
[0009]
The invention of claim 3 is characterized in that, in claim 1 or 2, a fuel injection pump connected to the pilot fuel injection valve is attached to a door of a cam chamber of a crankcase.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side sectional view of a cylinder head portion of a gas engine according to an embodiment. In the figure, 2 is a cylinder, 2a is a cylinder liner, 3 is a piston, 4 is a cylinder head, and the main combustion chamber 1 is surrounded by a piston 3, a cylinder liner 2a, and a cylinder head 4. In this example, a pre-combustion chamber unit 10 with a spark plug is disposed in the center of the cylinder head 4, and a pre-combustion chamber unit 30 with a pilot fuel injection valve is disposed on both sides.
[0011]
A pre-combustion chamber unit with spark plug (hereinafter sometimes simply referred to as “pre-combustion chamber with spark plug”) 10 is formed by incorporating a pre-combustion chamber nozzle 14 and a pre-combustion chamber main body 13 into the cylinder head 4. ing. Reference numeral 15 denotes a fuel injection hole for directly supplying fuel gas (pilot gas) into the precombustion chamber 12 secured in the precombustion chamber nozzle 14. The main combustion chamber 1 and the precombustion chamber 12 are communicated with each other through a plurality of communication holes 17 provided at the lower end of the precombustion chamber 12. A spark plug 11 is attached to the pre-combustion chamber body 13, and this serves as an ignition source for the air-fuel mixture in the pre-combustion chamber 12. The volume ratio of the pre-combustion chamber 12 of the pre-combustion chamber unit with spark plug 10 (ratio to the total combustion chamber volume at the time of compression top dead center) is reduced to a few percent to achieve ultra-low NOx.
[0012]
The pre-combustion chamber unit with pilot fuel injection valve (hereinafter also referred to simply as “pre-combustion chamber with pilot fuel injection valve”) 30 includes a pilot fuel injection valve 32 facing the pre-combustion chamber 31. The air-fuel mixture in the precombustion chamber 31 is ignited by injection of pilot fuel. The main combustion chamber 1 and the precombustion chamber 31 are communicated with each other by one or a plurality of communication holes 33 provided at the lower end of the precombustion chamber.
[0013]
In the case of this engine, the engine is started using the pre-combustion chamber 10 with a spark plug as a main ignition source. That is, since the diesel start is not performed, the pre-combustion chamber unit 30 with the pilot fuel injection valve can be made small. When the pilot oil amount is about 0.2 to 5% of the total heat amount ratio, the volume ratio of the precombustion chamber 31 can be reduced to about 1 to 3% of the whole. Therefore, it can be arranged on both sides of the cylinder head 4. This is a significant difference from the conventional pre-combustion type diesel engine in which the volume ratio of the pre-combustion chamber is designed to be 20 to 30%.
[0014]
The fuel injection pump connected to the pilot fuel injection valve 32 is attached to the door of the crankcase cam chamber as shown in FIGS. 2 and 3, 50 is a crankcase, 51 is a camshaft, 52 is a crankcase top surface, 53 is a cam chamber door, and 54 is a cam surface inspection window. A fuel injection pump is attached to the seat of the cam chamber door 53. 60 is provided. In this case, since the pilot oil amount is very small, about 0.2 to 5% with respect to the rated injection amount when diesel operation is assumed, the fuel injection pump is much smaller than that for a general diesel engine. 60 is attached.
[0015]
Next, the operation mode will be described.
As operation mode,
(1) Pre-combustion chamber type gas engine by spark ignition (2) Pilot ignition gas engine (3) Two types of ignition sources (spark ignition, pilot ignition) gas engine can be arbitrarily selected. There are a plurality of ignition sources and methods, and since these are parallel systems, the reliability of the ignition sources is increased.
[0016]
Actually, it is desirable to use spark plug ignition at start-up and pilot injection ignition at load, so that the combustion efficiency can be improved positively, but even if spark ignition is stopped at load There is no problem in driving.
[0017]
(1) In operation mode with spark ignition:
In this operation mode, only gaseous fuel (gas) is used as the fuel, and the pre-combustion chamber with spark plug is used as an ignition source for the mixture of gaseous fuel and air in the main combustion chamber 1.
Specifically, from the second half of the exhaust stroke to the first half of the intake stroke, the pilot gas is supplied into the precombustion chamber 12 from the fuel injection hole 15 of the precombustion chamber unit 10 with spark plug (the following symbols are shown in FIG. 1). . The pilot gas is supplied by a differential pressure between a pressure in a pilot gas header (not shown) and a pressure in the main combustion chamber 1, and the amount thereof is adjusted by changing the differential pressure. The main combustion chamber is supplied with a mixture of fuel gas and air during the intake stroke. In the compression stroke, the lean mixed gas in the main combustion chamber 1 is compressed by the piston 3, so that a part of the mixed gas passes through the communication hole 17 of the pre-combustion chamber unit 10 with the spark plug. Flow into. During the inflow, the fuel gas in the precombustion chamber 12 and the lean air-fuel mixture are mixed, and the concentration becomes an average excess air ratio of about 1.0. When this state is reached, spark discharge is generated between the gaps of the spark plug 11, and the air-fuel mixture in the pre-combustion chamber is ignited and burned. The flame burned in the pre-combustion chamber 12 propagates to the main combustion chamber 1 and becomes an ignition source of the air-fuel mixture in the main combustion chamber 1, and burns the entire air-fuel mixture in the main combustion chamber 1.
[0018]
(2) In the operation mode of ignition by pilot fuel injection:
In this operation mode, although gaseous fuel is used as the main fuel, liquid fuel is used as the pilot fuel as the auxiliary fuel. Then, pilot oil is injected from the pilot fuel injection valve 32 into the precombustion chamber 31 of the precombustion chamber unit 30 with pilot fuel injection valve. That is, when a mixture of fuel and air is supplied to the main combustion chamber 1 in the intake stroke, the lean mixture in the main combustion chamber 1 is compressed by the piston 3 through the precombustion chamber communication hole 33 in the compression stroke. It flows into the precombustion chamber 31. Therefore, a small amount of fuel oil is injected from the pilot fuel injection valve 32 around 10 to 30 ° (crank angle) immediately before the top dead center. Then, the injected fuel is ignited and burned, and this serves as an ignition source to ignite and burn the air-fuel mixture. Then, the flame burned in the pre-combustion chamber 31 propagates to the main combustion chamber 1 and becomes an ignition source of the air-fuel mixture in the main combustion chamber 1, and the entire air-fuel mixture in the main combustion chamber 1 is combusted.
[0019]
Fig. 4 shows the results of performance tests (changes in net thermal efficiency and NOx / smoke degree) while changing the amount of pilot fuel oil. Various combustion systems (dual fuel engine, diesel engine, pre-combustion chamber system spark ignition gas engine) It shows in comparison with. From this figure, the engine performance with pilot fuel injection achieves the same level of exhaust gas properties (NOx and dust) as the pre-combustion chamber type spark ignition gas engine, but the thermal efficiency is higher than that of spark ignition, which is the same as that of a diesel engine. It turns out that it is a level.
[0020]
In the case of pilot fuel injection, pilot gas in the pre-combustion chamber 10 with the spark plug is not necessary. Further, since the pilot oil amount can be about 0.2 to 5% of the total heat amount ratio, even if it is always injected, it does not affect the governing. Therefore, the rack of the fuel injection pump can be fixed, and a complicated link mechanism is unnecessary. Further, the speed control during engine operation can be performed by adjusting the amount of fuel gas with an engine governor.
[0021]
(3) Hybrid ignition gas engine operation mode:
In this operation mode, in the same combustion cycle, the central pre-combustion chamber 10 with spark plug and the pre-combustion chambers 30 with pilot fuel injection valves on both sides are operated almost simultaneously or slightly shifted, and these are used as ignition sources. The air-fuel mixture in the main combustion chamber 1 is combusted. Therefore, combustion promotion of the air-fuel mixture by multipoint ignition can be realized. Furthermore, by optimally adjusting the spark ignition timing and pilot fuel injection timing and the injection amount of these ignition sources, the combustibility of the air-fuel mixture is improved, and the effect of improving the thermal efficiency by short-term combustion can be obtained.
[0022]
Thus, the effect of rapid combustion by multi-point ignition when operating in the hybrid ignition gas engine mode will be supplemented.
FIG. 5 (a) shows the results of a comparative experiment of the heat generation rate of the single combustion chamber method (method of only the main combustion chamber having no precombustion chamber) and the precombustion chamber method (in the case similar to this embodiment). Show. In FIG. 5A, PCC indicates a pre-combustion chamber system, and OC indicates a single combustion chamber system. However, in the case of OC, the case of one spark plug = OC (1 Spark Plug) and the case of two spark plugs = OC (2 Spark Plugs) were also compared. In the experiment, as shown in FIG. 5B, first and second spark plugs (Spark Plugs) A and B are arranged at the center and side, and in the case of one spark plug, only the center spark plug A is provided. In the case of two spark plugs, both spark plugs A and B were used.
[0023]
The heat release rate pattern shown in FIG. 5 (a) shows that multi-point ignition (in the case of two spark plugs) and generation of strong ignition energy (in the case of PCC having a precombustion chamber as an ignition source) are rapid. It proves to be a very effective technique for realizing combustion. In other words, if the number of spark plugs is 2 (dashed line in the figure), heat generation is completed by around 40 degrees after top dead center, and compared with one spark plug (dashed line in the figure), short-term combustion is achieved. You can see that In addition, according to the pre-combustion chamber method (solid line in the figure) having stronger ignition energy, heat generation is completed by around 30 degrees after top dead center, and it can be seen that short-term combustion can be realized. Since short-term combustion contributes to improvement of thermal efficiency, it is possible to contribute to improvement of combustion by arranging a large number of ignition sources (three pre-combustion chambers) having strong ignition energy as in this embodiment. And high thermal efficiency can be realized.
[0024]
By the way, when comparing the ignition energy, it is about 0.1 J when only the spark plug is used, but in the case of a pre-combustion chamber with a spark plug (pre-combustion chamber volume ratio 2%), the amount of heat of the supplied fuel gas is Since it can be set as ignition energy, it becomes 3000J. In the case of pilot injection, if the amount of oil in the pilot fuel is 1% of the total heat quantity ratio, it will be about 600 J. Therefore, it can be seen that the multipoint ignition by the pre-combustion chamber 10 with the spark plug and the pre-combustion chamber 30 with the pilot fuel injection valve contributes to the improvement of combustion.
[0025]
In the above-described embodiment, the case where the pre-combustion chamber 10 with the spark plug is disposed in the center and the pre-combustion chamber 30 with the pilot fuel injection valve is disposed on both sides is shown. The chamber 30 may be disposed, and the pre-combustion chamber 10 with a spark plug may be disposed on both sides.
[0026]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, the cylinder head has a spark plug-equipped precombustion chamber that serves as an ignition source of the air-fuel mixture in the main combustion chamber and a total heat amount ratio of 0.2 to 5%. Since a pilot fuel injection valve for injecting a pilot oil amount is provided and a pre- combustion chamber with a pilot fuel injection valve serving as an ignition source of the air- fuel mixture in the main combustion chamber , ignition by spark ignition, ignition by pilot fuel injection, Any one of the two simultaneous ignition modes can be arbitrarily selected. Therefore, by using ignition plug ignition at the time of start-up and further pilot injection ignition at the time of load, high engine thermal efficiency can be obtained while maintaining low NOx, thereby reducing the low pollution (low CO2) of the gas engine. Can be used. According to the invention of claim 3, even a small fuel injection pump can be installed without any special modification of the crankcase.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a main part of a gas engine according to an embodiment of the present invention.
FIG. 2 is a plan view showing an attached state of the fuel injection pump in the gas engine according to the embodiment of the present invention.
3 is a view taken in the direction of arrows III-III in FIG. 2;
FIG. 4 is a characteristic diagram used for explaining the performance of the engine of the embodiment.
FIG. 5 is a characteristic diagram used for explaining the performance of the engine, in which (a) is a comparison diagram of heat generation rates of the single combustion chamber method and the precombustion chamber method, and (b) is a plane showing the location of the ignition plug. FIG.
[Explanation of symbols]
1 Main Combustion Chamber 2 Cylinder 3 Piston 4 Cylinder Head 10 Precombustion Chamber Unit with Spark Plug (Precombustion Chamber with Spark Plug)
11 Spark plug 12 Precombustion chamber 30 Pilot fuel injection valve precombustion chamber unit (Pilot fuel injection valve precombustion chamber)
31 Pre-combustion chamber 32 Pilot fuel injection valve 53 Cam chamber door 60 Fuel injection pump

Claims (3)

A gas engine for obtaining a driving output by supplying gaseous fuel to a main combustion chamber defined by a piston, a cylinder, and a cylinder head and burning the gas fuel, wherein an ignition source of an air-fuel mixture in the main combustion chamber is supplied to the cylinder head A pre-combustion chamber with an ignition plug, and a pilot fuel injection valve that is a pilot fuel injection valve that injects a pilot oil amount of 0.2 to 5% of the total heat ratio, and serves as an ignition source of the air- fuel mixture in the main combustion chamber A pre-combustion chamber type gas engine characterized by comprising a pre-combustion chamber.   In the same combustion cycle, the pre-combustion chamber with a spark plug and the pre-combustion chamber with a pilot fuel injection valve are operated almost simultaneously or slightly shifted, and the air-fuel mixture in the main combustion chamber is combusted using these as ignition sources. The pre-combustion chamber type gas engine according to claim 1, wherein   The pre-combustion chamber type gas engine according to claim 1 or 2, wherein a fuel injection pump connected to the pilot fuel injection valve is attached to a door of a cam chamber of a crankcase.

Images