JP2635764B2 - Fuel switching method for multi-fuel engine - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a fuel switching method for a multi-fuel engine.

[Prior art] Conventionally, gas fuel having high combustion efficiency is used in normal times, and operation is continued by switching to pre-stored liquid fuel in an emergency when gas fuel cannot be supplied due to an earthquake or accident. Multi-fuel agencies are known.

When switching from the gas fuel use state by spark ignition to the liquid fuel use state by compression ignition, the multi-fuel engine performs abnormal combustion by mixing pre-combustion combustion of spark ignition and diffusion combustion of compression ignition in one cylinder. In order to avoid such a situation, stop the engine for several tens of seconds or temporarily shut off the engine output as no-load operation, during which the supply of gas fuel to the entire engine is stopped, and then the liquid The compression ignition operation is started by supplying fuel to the entire engine.

[Problems to be Solved by the Invention] However, in the case of a multi-fuel engine requiring continuous engine output at all times, for example, a multi-fuel engine for driving a generator, there is a temporary problem when switching from gas fuel to liquid fuel. There is an inconvenience that a power outage state for several tens of seconds is caused by stopping the engine output.

The present invention has been made in view of the above circumstances, and provides a fuel switching method for a multi-fuel engine that switches from gas fuel to liquid fuel while maintaining a minimum output without interrupting engine output. It is intended to be.

Means for Solving the Problems According to the present invention, in a fuel switching method for a multi-fuel engine which can be used by switching from premixed combustion of gas fuel by spark ignition to diffusion combustion of liquid fuel by compression ignition, each engine cylinder is required. The fuel is switched by dividing the unit into units, shutting off the gas fuel with a time lag for each unit, scavenging for several cycles, supplying the liquid fuel, and simultaneously switching the ignition system from spark ignition to compression ignition. Thus, the engine output is continued in the engine cylinders of the units other than the engine cylinder of the unit being switched.

[Operation] Therefore, in the present invention, each engine cylinder in the multi-fuel engine is switched from gas fuel operation by spark ignition to liquid fuel operation by compression ignition at predetermined time intervals for each predetermined unit, and the output of the entire multi-fuel engine is changed. Even during the switching operation, the output of the engine cylinder is reduced by one unit, the engine output is continued without interrupting, and the used fuel is switched from gas fuel to liquid fuel while ensuring the minimum output.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

1 to 4 show an example of an apparatus for carrying out the method of the present invention. In the figures, a six-cylinder multi-fuel engine is shown as an example.

As shown in FIG. 1, a gas fuel supply line 1 for introducing gas fuel mixed with air in advance is connected to a gas fuel supply pipe 3 with an engine via a gas fuel cutoff valve 2. Gas fuel supply branch pipes 7, 8, 9 branched from the gas fuel supply pipe 3 with engine.
Are engine cylinders a, via gas fuel supply valves 4, 5, 6, respectively.
Connected to b, c, d, e, f.

In addition, a liquid fuel supply line 10 for guiding liquid fuel to be added to air separately supplied is connected to a liquid fuel supply pipe 12 with an engine via a liquid fuel cutoff valve 11. Liquid fuel supply branch pipes 16, 17, 18 branched from the engine-equipped liquid fuel supply pipe 12.
Are connected to the engine cylinders a, b, c, d, e, f via liquid fuel supply valves 13, 14, 15, respectively.

Further, the gas fuel supply pipes 4, 5, 6 and the liquid fuel supply valve 1
3, 14 and 15 are respectively connected to the fuel supply valve control device 20 via connection cords 19, and are individually opened and closed by signals from the fuel supply valve control device 20, respectively, and correspond to the corresponding engine cylinders a and b. , C and d, e and f as one unit, so that fuel switching can be controlled for each unit.

 In the figure, 21 indicates a switching command.

In FIGS. 2 to 4, black valves indicate a closed state, hatched engine cylinders indicate a gas fuel combustion state, and horizontal line engine cylinders indicate a liquid fuel combustion state.

Hereinafter, the fuel switching operation for implementing the method of the present invention will be described.

In the gas fuel use state, as shown in FIG. 2, the liquid fuel cutoff valve 11 and the liquid fuel supply valves 13, 14, 15 are closed, and the gas fuel cutoff valve 2 and the gas fuel supply valves 4, 5, 6 are opened. To perform gas fuel operation by premix combustion.

In such a state, the switching command 21 to the fuel supply valve controller 20 is given.
Is supplied, the gas fuel supply valve 4 that supplies gas fuel to the units of the engine cylinders a and b is closed by the signal of the fuel supply valve control device 20, and the fuel supply to the units of the engine cylinders a and b is performed. Is shut off.

At this time, the units of the engine cylinders a and b temporarily become zero output, but the engine cylinders of other units
c, d, e, f continuously output.

The engine cylinders a and b are operated for several cycles in a state in which the fuel supply is cut off to scavenge residual gas therein, and thereafter, the liquid fuel cutoff valve 11 and the liquid fuel supply valve 13 are opened to supply the liquid fuel. At the same time, the mode is switched from spark ignition to compression ignition to cause the units of the engine cylinders a and b to perform liquid fuel operation by diffusion combustion.

Next, the gas fuel supply valve 5 that supplies gas fuel to the units of the engine cylinders c and d is closed to shut off the fuel supply,
The residual gas is scavenged as described above.

At this time, as shown in FIG. 3, the engine cylinders a and b are in liquid fuel operation, the engine cylinders c and d are in scavenging,
e and f are gas fuel operation, engine cylinders a and b for diffusing and burning liquid fuel by compression ignition in one multi-fuel engine, engine cylinders c and d with zero output, and gas ignition by spark ignition. Engine cylinders e and f for premix combustion of fuel
Are mixed.

Next, similarly to the engine cylinders a and b, the units of the engine cylinders c and d and the units of the engine cylinders e and f are sequentially switched to the liquid fuel operation with a time lag, and finally all the engine cylinders a, b, and Let c, d, e, f be liquid fuel operation. At this point, the gas fuel cutoff valve 2 is closed, and the switching operation from gas fuel to liquid fuel is completed (see FIG. 4).

Therefore, according to the above, each of the engine cylinders a, b, c, d, e, and f in the multi-fuel engine is switched from the gas fuel operation by spark ignition to the liquid fuel operation by compression ignition with a time lag for each unit. Therefore, the output of the entire multi-fuel engine is reduced only by one unit during the switching operation, continues without interrupting the engine output, and can perform fuel switching while securing the minimum output.

In the above-described embodiment, the switching is sequentially performed with two engine cylinders as one unit. However, one engine cylinder may be one unit, or three or more engine cylinders may be one unit. The smaller the number of cylinders, the smaller the output reduction during the switching operation.

That is, the output reduction amount during the switching operation is ΔP for the output reduction amount during the switching operation, P is the total output for one multi-fuel engine, n is the number of engine cylinders for one unit, and all engine cylinders for one multi-fuel engine are If the number is Z, Therefore, in consideration of the above equation, the number of cylinders Z per unit can be maintained so that the required minimum output can be maintained.
, A desired minimum output can be easily secured.

It should be noted that the fuel switching method of the multi-fuel engine of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the fuel switching method for a multi-fuel engine of the present invention, the following various excellent effects can be obtained.

(I) Fuel switching can be performed while the engine output is continued without being temporarily interrupted.

(II) The output of the engine cylinder for one unit can be reduced even during the fuel switching operation, and the minimum output can be easily secured.

(III) After shutting off gas fuel for each unit and purging several cycles, liquid fuel is supplied, and at the same time, the ignition method is switched from spark ignition to compression ignition, so that abnormal combustion can be reliably prevented. it can.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of an apparatus for performing the method of the present invention, FIG. 2 is a flow sheet showing a gas fuel use state, FIG. 3 is a flow sheet showing a state during fuel switching,
FIG. 4 is a flow sheet showing a completed state of the fuel switching operation. In the figure, 1 is a gas fuel supply line, 2 is a gas fuel cutoff valve,
3 is a gas fuel supply pipe with an engine, 4, 5, and 6 are gas fuel supply valves,
7, 8 and 9 are gas fuel supply branches, 10 is liquid fuel supply line, 1
1 is a liquid fuel cutoff valve, 12 is a gas fuel supply pipe with engine, 13,1
4,15 are liquid fuel supply valves, 16,17,18 are liquid fuel supply branches,
Reference numeral 20 denotes a fuel supply valve control device, and reference numerals a, b, c, d, e, and f denote engine cylinders.

Claims (1)

(57) [Claims] In a fuel switching method for a multi-fuel engine which can be used by switching from premixed combustion of gas fuel by spark ignition to diffusion combustion of liquid fuel by compression ignition, each engine cylinder is divided into required units. After switching off the gaseous fuel and scavenging for several cycles with a time lag between each unit, the liquid fuel is supplied, and at the same time, the ignition system is switched from spark ignition to compression ignition, and the fuel is switched. A fuel switching method for a multi-fuel engine, wherein the engine output is continued in an engine cylinder of a unit other than the engine cylinder of the unit.