JPH0467564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixture supply method applied to a gas engine equipped with a carburetor that uses gasoline, kerosene, LPG, or the like as fuel.

The air-fuel mixture supply method in a gas engine is roughly divided into a continuous supply method using a carburetor and a timing supply method using an injection nozzle.

The former continuous supply method (a) does not require precision parts such as fuel injection pumps and injection valves and is easy to handle.

(b) Since no injection pump is used, there is no need for a driving device for this, and the overall structure is simple.

(c) Low cost.

(d) Good mixture of air-fuel mixture.

(E) It is easy to obtain the proper mixture ratio at the time of starting, and the starting characteristics are good.

It has these advantages and is mainly used in small gas engines with a bore of 200 mm or less.

In addition, the latter timing supply method (a) allows a wide range of mixture ratio adjustment (setting), and evenly distributes the mixture.

(b) Since there is no restriction in the intake system, the intake efficiency is good.

(c) Transient characteristics such as acceleration and deceleration of the engine are improved,
Responsiveness becomes better.

(d) Fuel can be adjusted.

(e) Exhaust gas characteristics are improved.

(f) There is no air-fuel mixture blow-through during the polymerization period (valve overlap) when the supply and exhaust valves are opened.

(g) Since the valve overlap period can be maintained at the same level as conventional diesel engines, the heat load on the piston, etc. is lower than in the former continuous supply system.

It has these advantages and is mainly used in medium and large gas engines with bores larger than 200 mm.

By the way, the above-mentioned continuous supply method and timing supply method have each other's advantages and disadvantages, and in the end,
Overall, it can be said that there are advantages and disadvantages.

An object of the present invention is to provide a mixture supply method in which a continuous supply method and a timing supply method are used in combination, in which the advantages of these methods are exhibited and the disadvantages are compensated for.

In order to achieve the above object, the present invention provides an air manifold that connects the air supplied from the supercharger to the port of the scavenging valve, which is equipped with a scavenging amount adjustment valve immediately after leaving the air cooler; The air pipe connected to the carburetor is divided into two systems, and the air is sent to the scavenging valve port and the carburetor, and it operates according to the air supply pressure of the air pipe to adjust the fuel gas supply pressure to adjust the air pressure and fuel pressure. The fuel gas is sent to the carburetor through a gas regulator that keeps the differential pressure constant.
The amount of air sent to the port of the scavenging valve and the carburetor is adjusted by the scavenging air amount adjusting valve and the air amount adjusting valve provided in the bypass pipe of the supercharger, while the air is exhausted near the top dead center of the piston. Just before the end of the process, the scavenging valve is opened to allow only air into the cylinder to scavenge the combustion gas, and almost at the same time as the exhaust valve is closed, the mixture valve is opened to supply the mixture obtained in the carburetor into the cylinder. However, one of the scavenging valve and the mixture valve is closed near the bottom dead center of the piston, and the other valve is closed at the same time as or before the one valve.

Examples of the present invention will be described below.

FIGS. 1 and 2 show a mixture supply device for implementing the mixture supply method of the present invention, and in the figures, 1 is a cylinder. This cylinder 1 includes a mixture valve 2, an exhaust valve 3, and a scavenging valve 4.
is provided and is configured to open and close in synchronization with the movement of a piston (not shown) inserted in combination into the cylinder 1 at a timing described later. Although a plurality of cylinders 1 are arranged in parallel, only one of them is depicted in the drawing.

A mixture manifold 5 is connected to the mixture valve 2, an exhaust manifold 6 is connected to the exhaust valve 3, and an air manifold 7 is connected to the scavenging valve 4. Further, a supercharger 9 equipped with a compressor 8 is provided at the exhaust end of the exhaust manifold 6, and the compressor 8 side of the supercharger 9 is connected to an air cooler 10. The air manifold 7 and the air supply end of the air supply pipe 11 are connected to the downstream side of the air supply pipe 10 .

On the other hand, the fuel gas supply pipe 12 is provided with a gas regulator 13.
and the air pipe 11 are connected to the mixture manifold 5 via the carburetor 14. The gas regulator 13 operates in response to the air supply pressure and adjusts the fuel gas supply pressure to keep the differential pressure between the air pressure Pa and the fuel gas pressure Pg constant. Therefore, the configuration is such that an air-fuel mixture with a constant air-fuel ratio is always obtained in the carburetor 14 regardless of an increase or decrease in the amount of air-fuel mixture. A connecting portion between the carburetor 14 and the mixture manifold 5,
Bypass pipe 15 of compressor 8 and air cooler 10
A mixture volume adjustment valve 16, an air volume adjustment valve 17, and a scavenging volume adjustment valve 18 are each individually provided at the connecting portion between the air manifold 7 and the air manifold 7.
The mixture amount adjustment valve 16 is controlled by a governor 19 as usual, and is controlled by the engine speed (engine output).
is being adjusted.

Here, an example of the opening/closing timing of the mixture valve 2, exhaust valve 3, and scavenging valve 4 is shown in the third example.
To explain with a diagram, in this diagram, TDC indicates the top dead center of the piston, and BDC indicates the bottom dead center of the piston.

First, the exhaust valve 3 opens at time t ₁ at the end of the combustion stroke, before the piston reaches the bottom dead center, and closes at time t ₃ when the exhaust stroke ends and the piston passes the top dead center and enters the intake stroke. Further, the scavenging valve 4 opens at time _t2 at the end of the exhaust stroke, before the piston reaches the top dead center, and closes at time _t4 , when the intake stroke ends and the piston passes the bottom dead center and enters the compression stroke. Further, the mixture valve 2 opens at time _t3 simultaneously with the closing of the exhaust valve 3, and closes together with the scavenging valve 4 at time _t4 .

Next, a method for supplying a mixture according to the present invention, which is carried out by the mixture supply device configured as described above, will be explained.

The air is compressed by the compressor 8 of the supercharger 9 operated by exhaust gas, then cooled by the cooler 10 and enters the carburetor 14, where the fuel is sent to the carburetor 14 through the gas regulator 13. Together with the gas, the mixture becomes a mixed gas having a predetermined air-fuel ratio, passes through the mixture manifold 5, and is sucked into the cylinder 1 through the mixture valve 2. As mentioned above, the timing when the mixture valve 2 opens is when the piston passes the top dead center and enters the intake stroke, and the exhaust valve 3 closes.
This is the _t3 position. Shortly before the mixture valve 2 opens and the mixture enters the cylinder 1, that is, before the piston on the exhaust stroke reaches top dead center, the scavenging valve 4 is opened and a portion of the air cooled by the cooler 10 is released. is fed into the cylinder 1 through the air manifold 7 to completely scavenge the combustion gases remaining in the cylinder out of the cylinder and at the same time cool parts facing the combustion chamber, such as the piston.

After the intake stroke ends and the compression stroke begins, and the piston passes the bottom dead center, the mixture valve 2 and the scavenging valve 4 are closed simultaneously, but the ratio of the mixture and air sent into the cylinder 1, that is, the final The air-fuel ratio can be obtained by adjusting the gas regulator 13 and adjusting the air-fuel ratio in the carburetor 14 and the openings of the air volume adjustment valve 17 and the scavenging volume adjustment valve 18. It is determined by the ratio to the air amount.

After the compression stroke, the engine enters the combustion stroke, and the exhaust valve 3 opens at the time _t1 , when the combustion stroke is nearing the end and before the piston reaches the bottom dead center, and exhaust begins. As already explained, the scavenging valve 4 is opened before the exhaust stroke ends, and the exhaust valve 3 is closed after the intake stroke begins, thus completing one cycle.

In the above configuration, the mixture valve 2 is opened at the same time as the exhaust valve 3 closes, but the mixture valve 2 may be opened a short time after the exhaust valve 3 finishes closing. good. Furthermore, although the air-fuel mixture valve 2 and the scavenging valve 4 are configured to close at the same time, one of the valves 2 (4) closes near the bottom dead center of the piston, and the other valve 4 (2) closes near the bottom dead center of the piston. It is also possible to implement the present invention by closing it earlier than that. When the scavenging amount adjustment valve 18 is completely closed, the gas engine shown in the figure operates as a continuous supply type gas engine with a carburetor.

On the other hand, when the air-fuel ratio of the air-fuel mixture obtained by the carburetor 14 is made extremely small (in a state where the gas concentration is high), the characteristics approach those of a timing supply type gas engine.

In addition, in the figure, air volume adjustment valve 1
7 is connected to the governor 19 at an appropriate link lever ratio, and circulates an appropriate amount of air after passing through the compressor 8 in response to the movement of the governor. Therefore,
The amount of air passing through the compressor 8 becomes larger than the amount of air sucked into the engine, and the surge margin of the supercharger 9 becomes larger. Particularly when the engine load is cut off, the mixture volume adjustment valve 16 of the carburetor 14 is close to fully closed, and the closed air pressure in the air pipe 11 rises rapidly, causing surging, but in this case, the above-mentioned By increasing the opening degree of the air volume adjustment valve 17 and increasing the circulating air volume, it is possible to suppress the occurrence of surging.

As explained above, the present invention allows air supplied from a supercharger to be connected to an air manifold immediately after exiting an air cooler, which is equipped with a scavenging amount adjustment valve and connected to a port of the scavenging valve, and to a carburetor. The air is sent to the scavenging valve port and the carburetor through two connected air pipes, which operate according to the air supply pressure of the air pipe to adjust the fuel gas supply pressure and create the differential pressure between the air pressure and fuel pressure. Fuel gas is sent to the carburetor via a gas regulator that keeps the amount constant, and the amount of air sent to the port of the scavenging valve and the carburetor is controlled by the air volume adjusting valve installed in the scavenging volume adjustment valve and the bypass pipe of the supercharger. On the other hand, it is adjusted by the valve and
Immediately before the end of the exhaust stroke near the top dead center of the piston, the scavenging valve is opened to allow only air into the cylinder to scavenge the combustion gas, and almost at the same time as the exhaust valve is closed, the air-fuel mixture valve is opened to generate the gas obtained in the carburetor. A configuration in which one of the scavenging valve and the mixture valve is closed near the bottom dead center of the piston, and the other valve is closed at the same time as or before the one valve. Therefore, it is possible to obtain a mixture with a constant air-fuel ratio regardless of the increase or decrease in the amount of the mixture, and it is possible to prevent blow-by of the mixture, and
It is possible to reduce the heat load on pistons, etc. and improve exhaust gas characteristics. Furthermore, the mixing ratio can be easily adjusted over a wide range, and an extremely lean mixture can be easily created, and the occurrence of surging during load shedding operation can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a gas engine to explain the mixture supply method of the present invention, FIG. 2 is a schematic diagram showing the relationship between the carburetor, mixture manifold, air manifold, etc. in FIG. 1, and FIG. FIG. 2 is a process chart showing an example of timings for opening and closing a mixture valve, an exhaust valve, and a scavenging valve. 1...Cylinder, 2...Mixture valve, 3...Exhaust valve, 4...Scavenging valve, TDC...Top dead center, BDC...
Bottom dead center.

Claims (1)

[Claims] 1 Immediately after the air supplied from the supercharger 9 exits the air cooler 10, the air manifold 7 is equipped with a scavenging amount adjustment valve 18 and connected to the port of the scavenging valve 4, and the air manifold 7 is connected to the carburetor 14. Air pipe 11
The air is sent to the port of the scavenging valve 4 and the carburetor 14, and operates in response to the air supply pressure of the air pipe 11 to adjust the fuel gas supply pressure and keep the differential pressure between the air pressure and the fuel pressure constant. The fuel gas is sent to the carburetor 14 through the gas regulator 13, and the amount of air sent to the port of the scavenging valve 4 and the carburetor 14 is sent to the scavenging amount adjusting valve 18 and the bypass pipe 15 of the supercharger 9. While the air volume is adjusted by the air volume adjustment valve 17 provided, the scavenging valve 4 is opened just before the end of the exhaust process near the top dead center (TDC) of the piston, and only air is admitted into the cylinder 1 to scavenge the combustion gas. Then, almost simultaneously with the closing of the exhaust valve 3, the mixture valve 2 is opened to supply the mixture obtained in the carburetor 14 into the cylinder 1,
A gas characterized in that either one of the scavenging valve 4 and the mixture valve 2 is closed near the bottom dead center (BDC) of the piston, and the other valve is closed at the same time as or before the one valve. Engine mixture supply method.