JPH04301183A - Methanol engine - Google Patents

Abstract

PURPOSE:To enable the perfect combustion of fuel by providing auxiliary combustion chambers comprising an auxiliary fuel valve and a main combustion chamber comprising a main fuel valve, in which axial line of the main injection is set in the swirl direction, and crossing the flame injected from injection ports of the auxiliary combustion chambers and the axial line of the main injection. CONSTITUTION:In an engine for large vessel, main combustion valves 7, 8 are provided symmetrically in both sides of an exhaust W, and auxiliary combustion chambers B1, B2 are inserted at right angle against a cylinder core. Methanol auxiliary fuel valves 1, 2 for ignition and glow plugs 2, 3 are installed to each auxiliary combustion chambers B1, B2, and the gas, which is ignited for burning, is injected from each injection port 5, 6 to a main combustion chamber A. At this stage, main injection Z1-Z3 of the main fuel valves 7, 8 are set so as to cross the center axis (m) of each injection port 5, 6 and form a vector in the same direction with the swirl direction V formed in the main combustion chamber A. Start of injection of the main fuel is adjusted at the timing delayed by 4-5 degree of crank angle from the start of injection of the auxiliary fuel.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber that uses methanol as fuel for large diesel engines for ships and the like.

0002

BACKGROUND OF THE INVENTION Conventionally, when methanol is used as fuel for a diesel engine, it has been necessary to burn it using a forced ignition device because methanol has a low cetane number, a high heat of vaporization, and poor self-ignition properties. Figure 3 is a vertical cross-sectional view of the combustion chamber of a conventional small methanol engine. Since the fuel valve 01 and the glow plug 02 were small and placed close together in the combustion chamber, good combustion was achieved.

0003

[Problems to be Solved by the Invention] However, there are many difficulties in adapting methanol fuel to large diesel engines. In other words, because the cylinder diameter of the engine is large, it is difficult for the injected methanol spray to mix with air, and the air-fuel ratio of the mixed gas is high (a lean mixture of 9:1 or more) and low (9:1 or less). In addition, because the distance between the fuel valve and the glow plug is long, the combustion state of the mixed gas is unstable, and the flame propagates easily in the rich mixture part, but the flame does not spread in the lean mixture part. They have the disadvantage that they are easily extinguished and are discharged as unburned gas, and because the cylinder diameter is large, the flame propagation time is long, making it impossible to ensure the amount of combustion within a certain period of time, resulting in poor thermal efficiency.

0004

[Means for Solving the Problems] The methanol engine of the present invention has a secondary combustion engine equipped with an auxiliary fuel valve, a glow plug, and nozzle portions 5 and 6, which are provided at an upper position of a cylinder liner symmetrical with respect to the cylinder center line of a large engine. Rooms B1 and B2,
main fuel valves 7 and 8 are provided at cylinder head positions symmetrical with respect to the cylinder center line, and the axes of the main spray injected into the main combustion chamber are mutually injected in a swirl direction;
The present invention is characterized in that the flame ejected from the nozzle of the auxiliary combustion chamber intersects the axis of the main spray of the main fuel valve, making it easy to ignite the main spray.

[0005]

[Operations] Since the present invention is constructed as described above, it exhibits the following functions. As shown in FIG. 1, methanol sprays C and D injected from the auxiliary fuel valves 1 and 2 before the end of the compression stroke of the piston Main combustion chamber A through 6
There are main fuel valves 7 and 8 in the main combustion chamber A downstream of the nozzle sections 5 and 6, which blow out methanol from the main fuel valves in accordance with the flame blowout from the nozzle sections of the auxiliary combustion chambers B1 and B2. It is possible to ignite and burn immediately after injection. In addition, as shown in Fig. 2, the main spray axes Z1, Z2, and Z3 from the main combustion valves 7 and 8 freely form swirl V with varying degrees of strength, resulting in good mixing of air and spray, and complete combustion. be.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a longitudinal sectional view of a methanol engine according to a first embodiment of the present invention. Large marine engines generally use a two-stroke uniflow scavenging system with a cylinder head U.
There is one exhaust valve W, and the main fuel valve 7 is located across the exhaust valve W.
, 8 are provided in symmetrical positions. Sub-combustion chambers B1 and B2 are inserted near the cylinder head and perpendicular to the cylinder axis. The sub-combustion chambers include methanol sub-fuel valves 1 and 2 exclusively for ignition. The gas ignited and burned in the auxiliary combustion chamber in which the glow plugs 3 and 4 are installed becomes a flame and is ejected into the main combustion chamber A through the nozzle portions 5 and 6. As shown in FIG. 2, main sprays Z1, Z2 of methanol ejected from the main fuel valves 7, 8,
Z3 is arranged so as to intersect the central axis m of the nozzle ports 5 and 6 of the auxiliary combustion chambers B1 and B2 and form a vector in the same direction as the swirl direction V formed in the main combustion chamber A. Since the injection start of the fuel valve is adjusted to be delayed by 4 to 5 degrees in crank angle from the injection start timing of the auxiliary fuel valve, complete ignition and combustion can be achieved. Further, the injection ports of the sub-combustion chambers are arranged downward as shown in FIG. 1, but in FIG. 2 they are arranged so that their central axes coincide with each other. Main spray axes Z1, Z of the main fuel valve 7 corresponding to the sub-combustion chamber B1
2 and Z3 intersect with the central axis m of the injection port 5, and the same is true for the main fuel valve 8 corresponding to the other sub-combustion chamber B2.

[0007]

Effects of the Invention The present invention provides small-volume auxiliary combustion chambers B1 and B.
2, the meethanol injected from the auxiliary fuel valves 1 and 2 is reliably combusted by the glow plugs 3 and 4, and the flame is jetted into the main combustion chamber, and the main spray Z1 in the swirl direction is jetted from the main fuel valves 7 and 8. , Z2, and Z3 can be reliably combusted, and a large methanol engine with high thermal efficiency can be provided.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a methanol engine according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a methanol engine according to a first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a conventional small methanol engine.

[Explanation of symbols]

01 Fuel valve 02 Glow plugs 1, 2
Sub-fuel valves 3, 4 Glow plugs 5, 6 Nozzle portions 7, 8 Main fuel valve A Main combustion chambers B1, B2 Sub-combustion chamber m Nozzle portion central axis W
Exhaust valve V Swirl direction X
Piston Z1, Z2, Z3 Main spray axis

Claims (1)

[Claims] Claim 1: An auxiliary combustion chamber (B1), ( B2), and main fuel valves (7) and (8) which are provided at cylinder head positions symmetrical with respect to the cylinder center line and whose axes of main spray injected into the main combustion chamber are injected in a swirl direction relative to each other. The methanol engine is configured such that the flame ejected from the injection port of the auxiliary combustion chamber and the axis of the main spray of the main fuel valve intersect, thereby facilitating ignition of the main spray.