JP2000064839A - Precombustion chamber system gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve combustibility of a lean-burn gas engine and to obtain higher engine thermal efficiency, maintaining NOx (nitrogen oxides) contained in exhaust to a lower degree. SOLUTION: By directing a communication hole 14 between a precombustion chamber 13 and a main combustion chamber 1 in a direction along swirl flow within the main combustion chamber 1 and inclining the direction of frame jet jetted from this communication hole 14 by a prescribed angle for a cylinder center line, combustion speed is increased by utilizing flow energy of swirl flow a combustion rate is improved and a fuel consumption rate is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a pre-combustion chamber type gas engine used as a stationary power generation facility for industrial or consumer use.

[0002]

2. Description of the Related Art Conventionally, in this type of pre-combustion chamber type gas engine, the pre-combustion chamber has been arranged at the center. For example, as a spark ignition type gas engine, as shown in FIG. 9, the main combustion chamber 1 includes a piston 2, a cylinder liner 3,
It is known that the cylinder head 4 is surrounded by the cylinder head 4 and the pre-combustion chamber unit 10 with a spark plug is arranged in the center of the cylinder head 4. In the pre-combustion chamber unit 10 with the spark plug, the pre-combustion chamber 13 is formed by incorporating the pre-combustion chamber injection port 11 and the pre-combustion chamber body 12 in the cylinder head 4. The main combustion chamber 1 and the pre-combustion chamber 13 have a plurality of communication holes 1 provided at the lower end of the pre-combustion chamber 13.
It is connected by 4. In the pre-combustion chamber 13,
A spark plug 15 is attached, and this spark plug 15
Serves as an ignition source for the air-fuel mixture in the pre-combustion chamber 13.
Reference numeral 16 is a fuel injection hole for directly supplying the fuel gas into the pre-combustion chamber 13. In the conventional spark ignition type gas engine configured as described above, the fuel gas is supplied from the fuel injection holes 16 into the pre-combustion chamber 13 in the latter half of the exhaust stroke and the first half of the intake stroke. This is called pilot gas, and this amount changes depending on the pressure difference between the pressure in the pilot gas header and the pressure in the main combustion chamber 1.
A mixture of fuel and air is supplied to the main combustion chamber 1 in the intake stroke. In the compression stroke, the piston 2 compresses the lean air-fuel mixture in the main combustion chamber 1 and the pre-combustion chamber 13
Flows into the pre-combustion chamber 13 via the communication hole 14. At the time of this inflow, the fuel in the pre-combustion chamber 13 and the lean air-fuel mixture are mixed, and the concentration becomes an average excess air ratio of about 1.0. In this state, spark discharge is generated between the gaps of the spark plug 15 to ignite and burn the air-fuel mixture. The flame generated in the pre-combustion chamber 13 propagates to the main combustion chamber 1 and serves as an ignition source for the air-fuel mixture in the main combustion chamber 1,
Burn the whole.

[0003]

In the conventional spark ignition type gas engine, the pre-combustion chamber 13 is arranged in the center as described above. This has the advantage that the structure of the cylinder head 4 can be simplified, but considering that the mixture combustion of fuel gas and air is carried out by flame propagation, a multi-point ignition system or swirl flow energy is used. To increase the burning rate,
It is considered to be the key to improving thermal efficiency. From this viewpoint, there is still room for pre-combustion chamber arrangement and design optimization of the communication holes between the pre-combustion chamber and the main combustion chamber.

The present invention has been made in view of the above circumstances. An object of the present invention is to improve the combustibility of a lean burn gas engine, and to reduce NO contained in exhaust gas.
An object of the present invention is to provide a pre-combustion chamber type gas engine that can obtain higher engine thermal efficiency while keeping x (nitrogen oxide) low.

[0005]

According to a first aspect of the present invention, a gas which obtains a driving output by supplying and burning a mixture of fuel and air to a main combustion chamber defined by a piston, a cylinder and a cylinder head. In the engine, the cylinder head is provided with a pre-combustion chamber that serves as an ignition source of an air-fuel mixture in the main combustion chamber, and a communication hole is formed between the pre-combustion chamber and the main combustion chamber. The connecting hole is provided in a direction along the swirl flow in the main combustion chamber, and the direction of the center line of the flame jet ejected from the connecting hole is set at a predetermined angle with respect to the cylinder center line. is there. According to claim 2 of the present invention, the direction of the center line of the flame jet ejected from the communication hole is 25 with respect to the cylinder center line.
The angle is set to ゜ to 35 ゜. Claim 3 of the present invention
Has a plurality of communication holes and is set so that flame jets ejected from these communication holes do not collide and interfere with each other.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 show an embodiment of the present invention. In these figures, the same components as those of the conventional example shown in FIG. In FIG. 1, a liquid fuel injection valve (main injection valve) 17 for diesel operation is arranged in the center of the cylinder head 4, and a pre-combustion chamber 13 equipped with a pilot fuel injection valve 18 is arranged on both sides. There is. In this way, the pre-combustion chambers 13 could be arranged on both sides because of the establishment of the technology for combustion by reducing the pre-combustion chamber volume ratio (ratio to the total combustion chamber volume at the compression top dead center) to several percent. It was realized. Further, the multiple pre-combustion chamber system with a small volume ratio realizes ultra-low NOx reduction. Further, the pilot fuel injection valve 18 serves as an ignition source of the air-fuel mixture in each pre-combustion chamber 13, and in this case, pilot gas is unnecessary, so that the fuel gas is directly fed into each pre-combustion chamber 13. The fuel injection hole for supplying is unnecessary. The main combustion chamber 1 and each pre-combustion chamber 13 communicate with each other through a communication hole 14 formed at the lower end of the pre-combustion chamber 13.

In the pre-combustion chamber type gas engine constructed as described above, the mixture of fuel and air is supplied to the main combustion chamber 1 during the intake stroke. Next, in the compression stroke, the lean air-fuel mixture in the main combustion chamber 1 is compressed by the piston 2 and flows into each pre-combustion chamber 13 via each communication hole 14. Furthermore, in the vicinity of 10 ° to 30 ° (crank angle) immediately before top dead center, each pilot fuel injection valve 1
A small amount of fuel oil is injected from 8, and this is ignited and burned.
Then, the air-fuel mixture is ignited and combusted using this as an ignition source. Then, the flame generated in the pre-combustion chamber 13 propagates to the main combustion chamber 1, becomes an ignition source of the air-fuel mixture in the main combustion chamber 1, and burns the entire main combustion chamber 1.

FIG. 3 shows the relationship between the direction of the communication hole 14 of the pre-combustion chamber 13 and the swirl flow direction. The swirl flow direction of this engine is clockwise as viewed from the upper surface of the cylinder head 4 (viewed by the arrow A in FIG. 1). Here, as shown in FIG. 2, a range formed by a line connecting the center O of the pre-combustion chamber 13 (processing center of the tip spherical surface portion) and the outer circumference circle of the communication hole 14 is a spread range of the flame jet (flame jet The range indicated by the spread angle θ) of And the center line L of this flame jet
The angle formed by 1 and the cylinder center line L3 is the angle numerical value shown in FIG. That is, in FIG. 3, (a)
The anti-swirl direction of 25 ° directs the communication hole 14 in the direction opposite to the swirl flow direction, and the angle formed by the flame jet centerline L1 and the cylinder centerline L3 is 2 °.
The angle formed by the center line L1 of the flame jet and the cylinder center line L3 is set to 0 °, (c), (d),
The swirl directions of 20 °, 25 °, and 35 ° in (e) respectively direct the communication holes 14 in the swirl flow direction, and the angles formed by the flame jet centerline L1 and the cylinder centerline L3 are 20 ° and 25 °, respectively. It was set at 35 °. In addition, in FIG. 2, reference numeral L2 indicates the center line of the pre-combustion chamber 13.

Next, a more concrete example of the pre-combustion chamber type gas engine configured as described above will be described. In this embodiment, the cylinder diameter is 2
A performance test was conducted using an engine having a stroke of 275 mm, a stroke of 275 mm, and a rotation speed of 1000 rpm as the combustion system of FIG.
The engine load during this test operation was BMEP1.4.
It was set to 7 MPa. Further, the tip of the pre-combustion chamber 13 is connected to the communication hole 1
The diameter of 4 was designed to be 8.5 mm × 1 and tested.

First, in FIG. 4, the communication hole 14 of the pre-combustion chamber 13 is shown.
The engine performance when the supply pressure is changed is compared using the direction of and the swirl flow direction as factors. Changing the supply pressure is the same as changing the excess air ratio. That is, reducing the supply pressure corresponds to reducing the excess air ratio, and is shown as a decrease in O ₂ concentration in FIG. As is clear from FIG. 4, the fuel consumption rate in the swirl direction of 25 ° to 35 ° is good. Swirl direction 20
The fuel consumption rate in the case of facing the angle is poor. Anti-swirl direction 2
5 ° represents these intermediate performances. This characteristic becomes more remarkable as the excess air ratio becomes smaller. From the direction of the flame jet in FIG. 3, the (b) facing and the (c) swirl direction 2
It is understood that 0 ° is the direction in which the flame jet collides, and the fuel consumption rate is poor. It is considered that this is because the flame jet caused energy loss due to collision to suppress the distribution over a wide area in the main combustion chamber 1, resulting in a longer combustion period and a change in the fuel consumption rate.

Further, FIG. 5 shows the connecting hole 14 of the pre-combustion chamber 13.
The engine performance when the pilot fuel oil is changed is compared using the direction of and the swirl flow direction as elements. When the amount of pilot fuel oil is reduced, the energy generated in the pre-combustion chamber 13, that is, the ignition energy for the main combustion chamber 1 becomes smaller. As can be seen in FIG. 5, swirl direction 2
The fuel consumption rate is good in the case of 5 ° to 35 °. The fuel consumption rate is poor when facing the swirl direction of 20 °. An anti-swirl direction of 25 ° shows these intermediate performances. This is considered to be the same as the above reason.

Further, FIG. 6 shows the relationship between the combination of the direction of the communication hole 14 of each pre-combustion chamber 13 and the swirl flow direction and the combustion period. The combustion period in the swirl direction of 25 ° to 35 ° is shorter than that in the swirl direction of 20 ° and the opposite and anti-swirl direction of 25 °. Further, as shown in FIGS. 4 and 5, the THC concentration in the exhaust gas is also 25 ° to 3 ° in the swirl direction.
5 ° is lower than the directional conditions of the other communication holes 14, demonstrating that the burning rate is good.

Although the present embodiment has been described with respect to the pre-combustion chamber type gas engine shown in FIG. 1, the present invention is not limited to this. For example, as shown in FIG. 7, a pre-combustion chamber with a spark plug is provided at the center of the cylinder head 4. Unit 30 and on both sides,
Pre-combustion chamber 13 equipped with the pilot fuel injection valve 18
Respectively, or as shown in FIG. 8, the liquid fuel injection valve (main injection valve) 17 is provided at the center of the cylinder head 4, and the pre-combustion chamber unit 31 with a spark plug is provided on both sides. It goes without saying that it is also applicable to those that are respectively arranged.

[0014]

According to the first aspect of the present invention, the communication hole between the pre-combustion chamber and the main combustion chamber is jetted from this communication hole in the direction along the swirl flow in the main combustion chamber. By inclining the direction of the flame jet to a predetermined angle with respect to the center line of the cylinder, the combustion energy is increased by utilizing the flow energy of the swirl flow, the combustion rate is improved, and the fuel consumption rate is improved. As a result, the combustibility of the lean burn gas engine can be improved, and higher engine thermal efficiency can be obtained while keeping the NOx contained in the exhaust gas low. According to the second aspect of the present invention, the flame jet ejected from the communication hole smoothly and quickly propagates into the main combustion chamber depending on the direction of the flame jet set at 25 ° to 35 ° with respect to the cylinder center line. By doing so, it is possible to shorten the combustion period and improve the fuel consumption rate. According to the third aspect of the present invention, by setting the directions of the flame jets ejected from the plurality of communication holes so as not to collide and interfere with each other, energy loss due to collision does not occur in the flame jet, and the flame jet The jet can be quickly distributed in the main combustion chamber, the combustion period can be shortened, and the fuel consumption rate can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a communication hole portion of a pre-combustion chamber.

FIG. 3 is an explanatory diagram showing a relationship between a direction of a communication hole of a pre-combustion chamber and a swirl flow direction.

FIG. 4 is a performance diagram showing engine performance when supply pressure is changed.

FIG. 5 is a performance diagram showing engine performance when the amount of pilot fuel oil is changed.

FIG. 6 is an explanatory diagram showing a comparison between a combination of a direction of a communication hole of a pre-combustion chamber and a swirl flow direction and a combustion period.

FIG. 7 is a sectional view showing another example of a combustion chamber structure of an engine to which the present invention is applied.

FIG. 8 is a sectional view showing another example of a combustion chamber structure of an engine to which the present invention is applied.

FIG. 9 is a sectional view of a conventional pre-combustion chamber type engine.

[Explanation of symbols]

1 Main Combustion Chamber 2 Piston 3 Cylinder Liner 4 Cylinder Head 13 Pre-combustion Chamber 14 Communication Hole L1 Flame Jet Centerline L3 Cylinder Centerline

Continued front page    (72) Inventor Sadao Nakayama             1-10-1 Kamatahonmachi, Ota-ku, Tokyo             Inside the Niigata Iron Works F term (reference) 3G023 AA02 AA05 AB05 AC05 AC07                       AD07 AD09 AD14 AD28

Claims (3)

[Claims] 1. A gas engine which obtains a driving output by supplying a mixture of fuel and air to a main combustion chamber defined by a piston, a cylinder and a cylinder head and burning the mixture, wherein the main combustion is carried out on the cylinder head. A pre-combustion chamber serving as an ignition source for the air-fuel mixture in the chamber is provided, a communication hole is formed between the pre-combustion chamber and the main combustion chamber, and the communication hole is formed in the swirl flow in the main combustion chamber. A pre-combustion chamber type gas engine, wherein the pre-combustion chamber type gas engine is provided along the direction along which the direction of the center line of the flame jet ejected from the communication hole is set at a predetermined angle with respect to the cylinder center line. 2. The pre-combustion chamber type gas engine according to claim 1, wherein the direction of the center line of the flame jet ejected from the communication hole is set to 25 ° to 35 ° with respect to the cylinder center line. 3. The pre-combustion chamber type gas according to claim 1, wherein the pre-combustion chamber type gas has a plurality of communication holes and is set so that flame jets ejected from these communication holes do not collide and interfere with each other. engine.