JPH11324805A - Precombustion chamber type gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an engine heat efficiency while holding low Nox by arranging a precombustion chamber with an ignition plug as an ignition source of mixture in a main combustion chamber on a cylinder head, and arranging precombustion chambers with a pilot fuel injection valve. SOLUTION: A precombustion chamber unit 10 with an ignition plug is arranged on a center part of a cylinder head 4. Precombustion chamber units 30 with a pilot injection valve are arranged on both sides of the cylinder head 4. Either one of a precombustion chamber type gas engine by spark ignition, a pilot ignition gaseous engine, two kinds of ignition sources (spark ignition, pilot ignition) is optionally selected as an operation mode. Ignition plug ignition at the time of start, and pilot injection ignition at the time of a load, are used together with each other, and thereby, it is possible to improve a combustion efficiency while holding low Nox .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-combustion chamber type gas engine which is useful mainly as a drive source for stationary power generation equipment.

[0002]

2. Description of the Related Art In recent years, lean-burn gas engines have attracted attention due to the demand for low pollution. Conventional lean burn gas engines mainly use a pre-combustion chamber system using a spark plug as an ignition source. Apart from this, an engine called a pilot injection gas engine (dual fuel engine) is also known. This engine has a structure in which pilot oil (liquid) having a ratio of about 5 to 15% of the total calorific value is directly injected into the main combustion chamber, and the fuel is burned using the fuel as an ignition source. This is achieved by injecting a small amount of pilot fuel from the main fuel injection valve of a typical diesel engine.

[0003]

The conventional gas engine with a pre-combustion chamber equipped with a spark plug is a combustion of a lean air-fuel mixture. Therefore, unless a strong ignition energy is applied, a combustion fluctuation accompanied by a misfire occurs. Sometimes. Also, when compared to diesel engines with the same cylinder diameter, NO
x is as low as about 1/10, which is advantageous for the environment, but has the disadvantage of low engine thermal efficiency.

Regarding the improvement of combustion fluctuations, various studies have been made on optimization of the position of a spark plug in the pre-combustion chamber and uniformization of mixed gas in the pre-combustion chamber in order to ensure combustion in the pre-combustion chamber. ing. However, since it does not contribute to an increase in ignition energy, there is a limit in improving engine thermal efficiency and combustion fluctuation.

[0005] Further, the conventional pilot injection gas engine has a limit in reducing NOx and dust, and has a drawback in that it cannot make full use of the low pollution of exhaust gas, which is an advantage of the gas engine.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a pre-combustion chamber capable of obtaining higher engine thermal efficiency while maintaining low NOx, thereby making use of the low pollution (low CO2) of a gas engine. It is an object of the present invention to provide a gas engine.

[0007]

A first aspect of the present invention is a gas engine which 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 gaseous fuel. The cylinder head is provided with a pre-combustion chamber with a spark plug and a pre-combustion chamber with a pilot fuel injection valve, which are ignition sources of the air-fuel mixture in the main combustion chamber.

According to a second aspect of the present invention, in the first aspect, the pre-combustion chamber with the ignition plug and the pre-combustion chamber with the pilot fuel injection valve are made to function substantially simultaneously or slightly shifted in the same combustion cycle, and these are operated. The mixture of the main combustion chamber is burned as an ignition source.

According to a third aspect of the present invention, in the first or second aspect, a fuel injection pump connected to the pilot fuel injection valve is attached to a door of a cam chamber of a crankcase.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of a cylinder head portion of the gas engine according to the 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 arranged at the center of the cylinder head 4 and a pre-combustion chamber unit 30 with a pilot fuel injection valve is arranged on both sides.

Pre-combustion chamber unit with spark plug (hereinafter sometimes simply referred to as "pre-combustion chamber with spark plug") 10
Is formed by incorporating the pre-combustion chamber injection port 14 and the pre-combustion chamber main body 13 into the cylinder head 4. Fifteen
Is a fuel injection hole for directly supplying a fuel gas (pilot gas) into the pre-combustion chamber 12 secured in the pre-combustion chamber injection port 14. The main combustion chamber 1 and the pre-combustion chamber 12 are connected by a plurality of communication holes 17 provided at the lower end of the pre-combustion chamber 12. An ignition plug 11 is mounted on the pre-combustion chamber main body 13 and 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 10 with a spark plug (the ratio to the total combustion chamber volume at the time of compression top dead center) is reduced to several percent, thereby realizing ultra-low NOx.

A pre-combustion chamber unit with a pilot fuel injection valve (hereinafter sometimes simply referred to as a “pre-combustion chamber with a pilot fuel injection valve”) 30 faces the inside of a pre-combustion chamber 31 and has a pilot fuel injection valve. 32, and ignites the air-fuel mixture in the pre-combustion chamber 31 by injection of pilot fuel. The main combustion chamber 1 and the pre-combustion chamber 31 are communicated by one or more communication holes 33 provided at the lower end of the pre-combustion chamber.

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 is not started, the size of the pre-combustion chamber unit 30 with the pilot fuel injection valve can be reduced. When the pilot oil amount is about 0.2 to 5% of the total calorific value ratio,
The volume ratio of the pre-combustion 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 because the volume ratio of the pre-combustion chamber of the conventional pre-combustion type diesel engine is 20 to 30%.
This is a major difference from the design.

A fuel injection pump connected to the pilot fuel injection valve 32 is mounted on a door of a cam chamber of a crankcase as shown in FIGS. FIG.
3, 50 is a crankcase, 51 is a camshaft,
52 is the top of the crankcase, 53 is the door of the cam chamber, 54
Reference numeral denotes a cam surface inspection window, and a fuel injection pump 60 is provided at a seat of a door 53 of the cam chamber. In this case, since the pilot oil amount is as small as about 0.2 to 5% of the rated injection amount assuming diesel operation, the fuel injection pump is very small as compared with a general diesel engine. 60 is attached.

Next, the operation mode will be described. As the operation mode, any one of (1) a pre-combustion chamber gas engine using spark ignition, (2) a pilot ignition gas engine, and (3) a two-type ignition source (spark ignition, pilot ignition) gas engine can be arbitrarily selected. Since there are a plurality of ignition sources and a plurality of methods, and they are arranged in parallel, the reliability of the ignition sources is increased.

In practice, it is desirable to use ignition plug ignition at the time of start-up and pilot injection ignition at the time of load, so that combustion efficiency can be positively improved. Even if you do, there is no problem in driving.

(1) In the operation mode by spark ignition:
In this operation mode, only gaseous fuel (gas) is used as fuel, and the pre-combustion chamber with a spark plug is used as an ignition source for a mixture of gaseous fuel and air in the main combustion chamber 1. Specifically, the pilot gas is supplied into the pre-combustion chamber 12 from the fuel injection holes 15 of the pre-combustion chamber unit 10 with a spark plug (hereinafter each reference numeral is shown in FIG. 1) from the latter half of the exhaust stroke to the first half of the intake stroke. . The pilot gas is supplied by a pressure difference 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 pressure difference. Further, a mixture of fuel gas and air is supplied to the main combustion chamber during an intake stroke. In the compression stroke, a part of the air-fuel mixture in the main combustion chamber 1 is compressed by the piston 3 so that a part of the air-fuel mixture is reduced.
It flows into the pre-combustion chamber 12 through the communication hole 17 of 0. At the time of inflow, the fuel gas and the lean gas mixture in the pre-combustion chamber 12 are mixed, and the concentration becomes about 1.0 as the average excess air ratio. In this state, a spark discharge is generated between the gaps of the ignition plug 11 to ignite and burn the air-fuel mixture in the pre-combustion chamber. The flame burned in the pre-combustion chamber 12 propagates to the main combustion chamber 1 and becomes an ignition source for the air-fuel mixture in the main combustion chamber 1.
The entire mixture in the main combustion chamber 1 is burned.

(2) In the operation mode of ignition by pilot fuel injection: In this operation mode, gas fuel is used as main fuel, but liquid fuel is used as pilot oil as auxiliary fuel. Then, pilot oil is injected from the pilot fuel injection valve 32 into the pre-combustion chamber 31 of the pre-combustion chamber unit 30 with the 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 main combustion chamber 1 is moved by the piston 3 in the compression stroke.
The lean mixture is compressed and flows into the pre-combustion chamber 31 through the pre-combustion chamber communication hole 33. So, just before top dead center,
A small amount of fuel oil is injected from pilot fuel injector 32 around 0 to 30 ° (crank angle). Then,
The injected fuel is ignited and combusted, and the mixture becomes the ignition source to ignite and combust. Then, the flame burned in the pre-combustion chamber 31 propagates to the main combustion chamber 1 and serves as an ignition source for the air-fuel mixture in the main combustion chamber 1 so that the entire air-fuel mixture in the main combustion chamber 1 burns.

FIG. 4 shows the results of performance tests (relationship between net thermal efficiency and NOx / smoke degree) while changing the pilot fuel oil amount, based on various combustion types (dual fuel engine, diesel engine, pre-combustion chamber type spark ignition). Gas engine). From this figure, it can be seen that the engine performance in the 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 the spark ignition and is the same as that of the diesel engine. It turns out that it is a level.

In the case of pilot fuel injection, pilot gas in the pre-combustion chamber 10 with a spark plug is not required. In addition, since the pilot oil amount can be set to a total heat amount ratio of about 0.2 to 5%, governing is not affected even if it is always injected. Therefore, the rack of the fuel injection pump may be fixed, and a complicated link mechanism is not required. In addition, speed control during engine operation can be performed by adjusting the amount of fuel gas by the engine governor.

(3) Hybrid ignition gas engine operation mode: In this operation mode, in the same combustion cycle, the central pre-combustion chamber 10 with a spark plug and the pre-combustion chambers 30 with pilot fuel injection valves on both sides are almost simultaneously. Alternatively, the gas mixture in the main combustion chamber 1 is burned using these as ignition sources. Therefore, it is possible to promote the combustion of the air-fuel mixture by the multipoint ignition. Furthermore, by optimally adjusting the spark ignition timing, pilot fuel injection timing, and injection quantity of these ignition sources, the combustibility of the air-fuel mixture is improved, and the effect of improving thermal efficiency by short-term combustion is obtained.

The effect of rapid combustion by multipoint ignition when operating in the hybrid ignition gas engine mode will be supplemented. FIG. 5 (a) shows the results of a comparison experiment of the heat release rate between the single combustion chamber system (only the main combustion chamber without a pre-combustion chamber) and the pre-combustion chamber system (similar to this embodiment). Is shown. In FIG. 5A, PCC indicates a pre-combustion chamber system, and OC indicates a single combustion chamber system. However, in the case of OC, one spark plug = OC (1 Spark Plug) and two spark plugs =
OC (2 Spark Plugs) was also compared. At the time of the experiment, as shown in FIG.
Second spark plugs (Spark Plugs) A and B were arranged. In the case of one spark plug, only the center spark plug A was used, and in the case of two spark plugs, both spark plugs A and B were used.

The heat release rate pattern shown in FIG. 5 (a) indicates multipoint ignition (in the case of two spark plugs) or generation of strong ignition energy (in the case of PCC using a pre-combustion chamber as an ignition source). Has proven to be a very effective technology for realizing rapid combustion. That is, when the number of spark plugs is set to two (dashed line in the figure), heat generation is completed by about 40 degrees after the top dead center. You can see that it is doing.
Further, according to the pre-combustion chamber system having a stronger ignition energy (solid line in the figure), heat generation is completed by around 30 degrees after the 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 having strong ignition energy (arranging three pre-combustion chambers) as in the present embodiment. And high thermal efficiency can be realized.

By comparison, the ignition energy is about 0.1 J in the case of only the spark plug,
In the case of the pre-combustion chamber with a spark plug (the pre-combustion chamber volume ratio is 2%), the heat quantity of the supplied fuel gas can be used as the ignition energy. In the case of pilot injection, the amount of oil in the pilot fuel is 1% of the total calorific value ratio.
Then, it becomes about 600J. 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 greatly contributes to the improvement of combustion.

In the above embodiment, the case where the pre-combustion chamber 10 with the ignition plug is arranged at the center and the pre-combustion chamber 30 with the pilot fuel injection valve is arranged at both sides is shown. The pre-combustion chamber with an ignition plug 30 may be arranged, and the pre-combustion chamber with an ignition plug 10 may be arranged on both sides.

[0026]

As described above, according to the first and second aspects of the present invention, the cylinder head is provided with a pre-combustion chamber with a spark plug and a pilot fuel injection valve, which serves as an ignition source for air-fuel mixture in the main combustion chamber. Since the pre-combustion chamber is provided, any one of the operation modes of ignition by spark ignition, ignition by pilot fuel injection, and simultaneous ignition of two types can be selected. Accordingly, high engine thermal efficiency can be obtained while maintaining low NOx by using the ignition plug ignition at the time of starting and the pilot injection ignition at the time of load, whereby the low pollution (low CO2) of the gas engine is achieved. Can be utilized. According to the third aspect of the present invention, even a small fuel injection pump can be installed without 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 a mounting state of a fuel injection pump in the gas engine according to the embodiment of the present invention.

FIG. 3 is a view taken in the direction of arrows III-III in FIG. 2;

FIG. 4 is a characteristic diagram used to explain the performance of the engine of the embodiment.

FIG. 5 is a characteristic diagram used to explain the performance of the engine,
(A) is a comparison diagram of the heat generation rates of the single combustion chamber system and the pre-combustion chamber system, and (b) is a plan view showing the location of the ignition plug.

[Explanation of symbols]

Reference Signs List 1 main combustion chamber 2 cylinder 3 piston 4 cylinder head 10 pre-combustion chamber unit with spark plug (pre-combustion chamber with spark plug) 11 spark plug 12 pre-combustion chamber 30 pilot fuel injector pre-combustion chamber unit (pilot fuel injector pre-combustion) Chamber) 31 pre-combustion chamber 32 pilot fuel injection valve 53 door of cam chamber 60 fuel injection pump

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02B 43/02 F02B 43/02 F02D 19/10 F02D 19/10 F02M 61/14 310 F02M 61/14 310P 310U F02P 13/00 303 F02P 13/00 303A (72) Inventor Takeyuki Sakagami 1-10-1 Kamatahonmachi, Ota-ku, Tokyo Inside Niigata Iron Works Co., Ltd.

Claims (3)

[Claims] 1. A gas engine for obtaining a drive output by supplying gaseous fuel to a main combustion chamber defined by a piston, a cylinder, and a cylinder head and burning the gaseous fuel. A pre-combustion chamber type gas engine comprising a pre-combustion chamber with a spark plug and a pre-combustion chamber with a pilot fuel injection valve, which serve as ignition sources for air. 2. 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 made to function substantially simultaneously or slightly displaced from each other, and the mixture in the main combustion chamber is used as an ignition source. The pre-combustion chamber type gas engine according to claim 1, wherein the gas is burned. 3. The pre-combustion chamber gas engine according to claim 1, wherein a fuel injection pump connected to the pilot fuel injection valve is mounted on a door of a cam chamber of a crankcase.