JPH0893476A - Large sized and low speed two cycle methanol engine - Google Patents

Abstract

PURPOSE: To improve the accelerating ability from standstill and the fuel consumption by forming the diameter of the upper and lower parts of an auxiliary combustion chamber and the insertion distance of a glow plug, the radial angle between glow plugs, etc., so as to satisfy the prescribed relationship in a large and low speed methanol engine having the glow plugs in the auxiliary combustion chamber. CONSTITUTION: In a large size and low speed methanol engine having glow plugs 3, 4 in an auxiliary combustion chamber B, each part is formed so as to simultaneously satisfy the inequalities of 35dn<=1G<=45dn, 23 deg.<=θ<=30 deg., 1.5<=D/d<=2.25, 0.65%<=η<=2.25% where d, D are the diameter of the upper and lower parts of the auxiliary combustion chamber B, 1G is the insertion distance of the glow plugs 3, 4, θ is the radial angle of two glow plugs in the auxiliary combustion chamber, dn is the diameter of the single injection port of an auxiliary fuel valve 1, η is the volume ratio of the total volume of the auxiliary combustion chamber B to the total volume of the combustion chamber formed by the top dead center. The large and low speed two-cycle engine excellent in the accelerating ability from standstill and the low fuel consumption and capable of 100% combustion of methanol can be obtained thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber of a large diesel engine which uses methanol as a fuel.

[0002]

2. Description of the Related Art FIG. 8 shows a cross-sectional view of a fuel system and a combustion chamber of a conventional methanol-fired low speed large engine. This figure shows two main fuel valves 7a and 8a and sub fuel valves 1a and 2a in one cylinder.
Is an example equipped with. The main fuel valves 7a and 8a are mounted on the cylinder cover, and the auxiliary fuel valves 1a and 2a are mounted on the upper side surface of the cylinder. The ignition glow plug 3 is provided near the auxiliary fuel valve.
a and 4a are attached.

The sub-combustion chambers 1a and 2a have the same nozzle holes 5a and 6a.
Through the main combustion chamber A. The main fuel is injected into the main combustion chamber A from the main fuel valves 7a and 8a. Sub fuel valve 1
When the fuel gas is injected from the a, 2a to the auxiliary combustion chamber B and the fuel is ignited and burned by the sparks of the ignition glow plugs 3a, 4a, the combustion gas is ejected from the injection ports 5a, 6a to the main combustion chamber A, and the main fuel is ejected. Ignition of the main fuel injected from the valves 7a and 8a,
To burn.

In the main combustion chamber A as described above, the volume of the auxiliary combustion chamber B is usually the total combustion chamber volume V _C formed at the top dead center.
It is determined by the ratio of the When (volume of sub-combustion chamber) / (total combustion chamber volume at top dead center) is defined as a volume ratio η, conventionally, the volume ratio η of the sub-combustion chamber B is 5 to 10%, and the sub-combustion chamber is Since there are two, the total volume ratio η was 10 to 20%.

[0005]

In the methanol diesel engine, the larger the volume of the auxiliary combustion chamber B,
Ignition of the methanol spray from the sub fuel valves 1a and 2a becomes easy, and the startability in the cold state is improved. Also, from the viewpoint of exhaust pollution, there is an advantage that the emission concentration of unburned hydrocarbons is reduced.

However, when the volume ratio of the sub-combustion chamber B increases, the specific surface area of the entire combustion chamber increases, and the fuel consumption rate (hereinafter abbreviated as fuel consumption rate) has a drawback. Further, the reliability is lowered and the cost is increased. Therefore, it is required to significantly reduce the volume ratio.

An object of the present invention is to provide a large-sized low-speed engine capable of 100% methanol combustion, and a methanol diesel engine excellent in startability and low fuel consumption rate.

[0008]

The large-sized low-speed two-cycle methanol engine of the present invention is a large-sized low-speed methanol engine having a glow plug in the auxiliary combustion chamber, wherein the upper auxiliary combustion chamber diameter of the auxiliary combustion chamber is d, the lower auxiliary combustion chamber diameter D, the axial insertion distance of the glow plug l _G, the radial angle of the mutual two said glow plug inserted into the auxiliary combustion chamber theta, a single injection aperture of the auxiliary fuel valve when dn and total volume of the auxiliary combustion chamber has a η volume ratio the ratio among all the combustion chamber volume formed by the top dead center, the _{l G, θ, D / d} ,
η is 35 dn ≤l _G ≤45 dn, 23 ° ≤θ≤
30 °, 1.5 ≦ D / d ≦ 2.25, 0.65% ≦ η ≦
It is characterized by satisfying 2.25% at the same time.

[0009]

As described above, the shape of the auxiliary combustion chamber is changed to (35dn ≤ l _G
≤ 45dn, 23 ° ≤ θ ≤ 30 ° and 1.5 ≤ D / d ≤
2.25) is maintained and the secondary combustion chamber volume ratio η = 0.65% to
When it is set to 2.25%, as shown in FIGS. 6 and 7, good results are obtained in cold start and fuel efficiency.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a fuel system and a combustion chamber of a methanol-fueled low-speed large-sized engine of the present invention, FIG. 2 is an explanatory diagram showing main dimensions of a sub-combustion chamber of the present application, FIGS. 3 to 7 show experimental results, and FIG. It is a diagram which made the engine load factor and relative HC concentration into the x and y axis.

FIG. 4 is a diagram in which the axial glow plug insertion distance l _G and the number of complete explosion initiation cycles after fuel injection are plotted on the x and y axes, and FIG. 5 is the auxiliary combustion chamber bore ratio D / d and completion after fuel injection. A diagram with the number of explosion start cycles on the x and y axes, FIG. 6 is a diagram with the auxiliary combustion chamber volume ratio η and the cooling start relative time ratio on the x and y axes, and FIG. 7 is the auxiliary combustion chamber volume ratio η. It is a diagram which made the relative fuel consumption rate the x-axis and the y-axis.

In the methanol-fueled low-speed large-sized diesel engine of FIG. 1, the volume ratio η is set inside the cylinder cover.
A sub-combustion chamber B having a structure is formed, and its details are as follows.

That is, the basic form of the auxiliary combustion chamber shown in FIG. 2 is (a)
The lower sub-combustion chamber B ₂ as shown in the figure is generally rectangular, but there is also a part where the part is tapered as shown in FIGS. In this embodiment, the shape of the auxiliary combustion chamber is determined by conducting an experiment focusing on the starting property and the low load region under the condition that the volume ratio η is 3% or less.

In the basic shape (a) of the auxiliary combustion chamber shown in FIG. 2, the diameter of the upper auxiliary combustion chamber B ₁ is d and the lower auxiliary combustion chamber B _{2 is}
Is D, the diameter of the single injection port of the auxiliary fuel valve is dn, the length of the lower auxiliary combustion chamber is l = 40dn, the length of the auxiliary combustion chamber before entering the throttle of the communication port 5 is L (Lmax = 90dn), and the axial glow The plug insertion distance is L _G, and the radial angle from the upper end center C of the upper auxiliary combustion chamber B ₁ to the glow plugs 3 and 4 is θ.

In the methanol diesel engine having the above structure, the shape of the auxiliary combustion chamber was variously changed, and FIG. 3 was used to confirm the relative HC concentration at low load by the axial glow plug insertion distance l _G and the radial angle θ. Obviously, θ = 23 ° to 30 ° is good, and deterioration is recognized on both sides. FIG. 4 confirms the number of complete explosion start cycles after the start of fuel injection, and l _G = 35dn to 45dn is 1
Ignition and combustion are surely reached from the cycle.

Further, FIG. 5 confirms the diameter ratio D / d of the auxiliary combustion chamber and the number of complete explosion start cycles. From this result, if the second cycle after fuel injection is allowed, 1.5 ≦ D
It can be seen that a satisfactory result can be obtained if /d≦2.25. Therefore, the shape of the auxiliary combustion chamber (Lma
x ≤ 90 dn, l = 40 dn) and 35 dn ≤ l _G ≤ 45
dn, 23 ° ≦ θ ≦ 30 °, 1.5 ≦ D / d ≦ 2.25
Then, since the startability and the fuel efficiency of low load are good,
This was proposed as the basic form of the auxiliary combustion chamber.

Next, the operation of the first embodiment will be described. Shape of the sub-combustion chamber proposed above (35dn ≤ l _G ≤ 45d
n, 23 ° ≦ θ ≦ 30 ° and 1.5 ≦ D / d ≦ 2.2
6 and 7 show the results of changing η = 0.5% to 5% while maintaining 5). FIG. 6 shows a survey of the startability in the cold state. It is a plot of the relationship between η and the cold start relative time ratio (t / t η = 5%) based on the time required to reach the 25% marine characteristic speed after the start operation at η = 5%. is there.

When (t / t η = 5%) ≦ 2 is an allowable value, η ≧ 0.65% is applicable. Furthermore, the relative fuel consumption rate (be / be η = 5) when these were operated at rated output
%) And η are shown in FIG. 7. When 0.65% ≦ η ≦ 1.75% when η = 5%, an improvement in fuel efficiency of 3% or less is recognized.

[0019]

By adopting the shape of the auxiliary combustion chamber proposed by the present invention, it is possible to provide a large-sized low-speed two-cycle engine capable of 100% methanol combustion excellent in startability and low fuel consumption rate.

[Brief description of drawings]

FIG. 1 is a sectional view of a combustion chamber according to a first embodiment of the present invention.

FIG. 2 is an explanatory view showing the basic shape of the auxiliary combustion chamber of the present application.

FIG. 3 is a diagram in which engine load factor and relative HC concentration are plotted on x and y axes.

FIG. 4 is a diagram in which the axial glow plug insertion distance l _G and the number of complete explosion start cycles after fuel injection are taken as x and y axes.

FIG. 5 is a diagram in which the auxiliary combustion chamber aperture ratio D / d and the number of complete explosion start cycles after fuel injection are plotted on the x and y axes.

FIG. 6 is a diagram in which the auxiliary combustion chamber volume ratio η and the cooling start relative time ratio are x and y axes.

FIG. 7 is a diagram in which the auxiliary combustion chamber volume ratio η and the relative fuel consumption rate are plotted on the x and y axes.

FIG. 8 is a prior art example corresponding to FIG. 1.

[Explanation of symbols]

A ... main combustion chamber, B ... auxiliary combustion chamber, B ₁ ... upper secondary combustion chamber, B
₂ ... Lower auxiliary combustion chamber, Z ... Main spray, 1 ... Secondary fuel valve, 3, 4
... glow plugs, 5 ... injection port portion, 7 ... main fuel valve, d ... upper secondary combustion chamber diameter, dn ... single injection aperture of the secondary fuel valves, D ... lower auxiliary combustion chamber diameter, l _G ... glow plug axial insertion distance , Θ ...
Mutual radius angle of glow plugs.

Claims (1)

[Claims] 1. In a large-sized low-speed methanol engine having a glow plug in the auxiliary combustion chamber, the upper auxiliary combustion chamber diameter of the auxiliary combustion chamber is d, the lower auxiliary combustion chamber diameter is D, and the glow plug axial insertion distance is set. L _G , the mutual radial angle of the two glow plugs inserted in the auxiliary combustion chamber is θ, the single injection port diameter of the auxiliary fuel valve is dn, and the total volume of the auxiliary combustion chamber is formed at the top dead center. When the ratio of the total combustion chamber volume to the total combustion chamber volume is η, the above-mentioned l _G , θ, D / d, η are 35 dn ≤ l _G ≤ 45 dn, 23 ° ≤ θ ≤ 30 °,
1.5 ≦ D / d ≦ 2.25, 0.65% ≦ η ≦ 2.25
A large-sized low-speed two-cycle methanol engine characterized by satisfying the same percentage at the same time.