JP2001082255A - Air supply pipe structure for multi-cylinder gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the uniformity of fuel supply between respective cylinder engines and to supply uniform swirl flows for the respective cylinders in a multi-cylinder gas engine. SOLUTION: This air supply pipe structure for the multi-cylinder gas engine is formed so that the inlet end of each of air supply ports 15 of respective cylinders may be connected to an air supply collecting pipe 1 through respective air supply branch pipes 12 respectively, and an injector 13 for gas fuel supply may be mounted on the respective air supply branch pipes 12. The length of the air supply branch pipe 12 is lengthened so that one gas fuel volume injected from the injector 13 may become almost one half or less as large as the total volume of the air supply branch pipe 12 and the air supply port 15 for each cylinder. The injector 13 is disposed on the downstream side of the air supply from the volume area of the air supply injected from the air supply collecting pipe 1 into the air supply branch pipe 12 at one time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fuel supply system for connecting a gas supply port of each cylinder to a supply manifold via a supply branch pipe. The present invention relates to an intake pipe structure of a multi-cylinder gas engine provided with an injector.

[0002]

2. Description of the Related Art A multi-cylinder gas engine is provided with a so-called multipoint injection system having an injector for supplying gas fuel to each supply branch pipe as described above, There is a method in which a single injector is provided at the inlet of the pipe, and after mixing the supply air and the gas fuel, the mixture is distributed from the supply manifold to each supply branch pipe.

In a multi-point multi-cylinder gas engine, gas fuel is injected into each cylinder, so that a theoretically uniform mixture can be supplied to each cylinder. However, due to changes in various conditions such as the volume, length, or shape of the air supply branch pipe, the mounting position of the injector, or the fuel injection direction, a part of the gas fuel injected into the air supply branch pipe of one cylinder is supplied. It may flow out through the air collecting pipe into the air supply branch pipe of another cylinder.

[0004] For example, as shown in FIG.
01 and the inlet end of the air supply port 115 of each cylinder are connected via a short air supply branch pipe 112, and the injector 11
In the air supply pipe structure in which 3 is disposed in the air supply branch pipe 112, the volume from the boundary P 1 between the air supply manifold 101 and the air supply branch pipe 112 to the air supply valve 120 is small, and Since the position is close to the air supply manifold 1, part of the gas fuel ejected from the injector 113 into the air supply branch pipe 112 flows directly into the air supply manifold 101, or A part of the air supplied once from the collecting pipe 101 into the air supply branch pipe 112 is supplied to the air supply collecting pipe 1.
When the fuel gas is pushed back to 01, a part of the gas fuel may flow into the air supply manifold 101.

As described above, when a part of the gas fuel injected into the supply branch pipe 112 of a certain cylinder flows out into the supply manifold 101, the gas fuel that has flowed out is supplied to the supply branch for another cylinder. After flowing into the pipe 112, the gas fuel supply amount varies among the cylinders, and abnormal combustion occurs in a cylinder having an excessive amount of fuel, and a knocking phenomenon may occur.

[0006] In particular, as in the gas engine described in Japanese Patent Application Laid-Open No. 9-158785, in order to uniformly mix the gas fuel and the supply air, a large number of injection directions are affected by the supply air pressure. By adopting a structure in which gas fuel is injected and most of the gas fuel collides against the air supply, part of the gas fuel can flow out from the air supply branch pipe to the air supply manifold as described above. And the variation of the gas fuel supply amount between the cylinders may increase.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to improve the structure of the air supply branch pipe so as to prevent gas fuel from intersecting between the cylinders and to uniformly supply fuel to each cylinder. Another object is to make the swirl flow of each cylinder uniform.

[0008]

According to a first aspect of the present invention, an inlet end of an air supply port of each cylinder is connected to an air supply manifold via an air supply branch pipe. In a supply pipe structure of a multi-cylinder gas engine in which a gas fuel supply injector is provided for each of the cylinders, a single fuel injection from the injector with respect to a total volume of a supply branch pipe and a supply port in each cylinder is performed. Is characterized in that the length of the air supply branch pipe is increased so that the volume of the air supply branch is approximately 1/2 or less.

According to a second aspect of the present invention, in the air supply pipe structure of the multi-cylinder gas engine according to the first aspect, the supply air is blown out from the air supply manifold into the air supply branch pipe at one time. It is characterized in that an injector is arranged in the air supply branch pipe portion on the air downstream side.

[0010]

FIG. 1 is a partial front view of a six-cylinder gas engine to which the present invention is applied. An intake manifold 1 is mounted on the front upper side of a cylinder head 2 in parallel with a crankshaft. One end of the supply air collecting pipe 1 in the longitudinal direction is connected to an intercooler 5 via a throttle valve 3, and the intercooler 5 is connected to an air intake device such as an air cleaner via a supercharger (not shown). The other end of the collecting pipe 1 is closed by a lid 6. The throttle valve 3 is connected to a rotary actuator 8 such as a motor, and the actuator 8 is connected to a control device so that the throttle opening can be adjusted.

The air supply manifold 1 is integrally formed with branch pipes 10 protruding downward at equally spaced positions in the longitudinal direction, and a cylinder head is provided at the lower end of each branch pipe 10. The extension pipes 11 that curve to the two sides are connected to each other, and the branch pipe 10 and the extension pipe 11 constitute an air supply branch pipe 12. An injector 13 for ejecting gaseous fuel is attached to each of the extension pipes 11.

FIG. 2 is a plan view of the air supply manifold 1. Each extension pipe 11 is provided with an air supply port 15 of each cylinder (only one is shown).
Connected to the entrance end of the The exhaust port 17 of each cylinder C
Are each provided with an exhaust gas temperature sensor 18.

FIG. 3 is an enlarged cross-sectional view taken along the line III-III of FIG.
The injector 13 is configured such that its axis O1
Are arranged so as to form a bisector of the curved portion. Specifically, it is attached to the extension pipe 11 from an obliquely lower direction at an angle of 45 ° with respect to the branch pipe center line O2, into which the nozzle pipe 20 of the injector 13 projects obliquely upward. I have.

The extension pipe 11 is interposed between the branch pipe 11 and the air supply port 15 in order to increase the volume of the entire air supply branch pipe 12 and lengthen the entire length of the air supply branch pipe 12. With the extension pipe 11 interposed, the volume of the air supply branch pipe 12 is determined by the volume V1 of the air supply branch pipe 12 (total volume of the branch pipe 10 and the extension pipe 11) V1 and the air supply port 15
The total volume V3 with the volume V2 of the
The gas fuel volume V4 ejected in one operation from 3 is approximately 1
/ 2 or less. Preferably, the length (volume) of the extension pipe 11 is set so that the gas fuel volume V4 is 35% or less of the total volume V3 of the supply branch pipe 12. The volume ratio set in this way is always substantially constant irrespective of an increase or decrease in output. That is, the gas fuel supply amount increases in proportion to the output, but the pressure in the air supply branch pipe 12 also increases in proportion to the output. , And is kept substantially constant irrespective of the increase or decrease in output.

The mounting position of the injector 13 is 1
The volume of the amount of air blown into the air supply branch pipe 12 from the air supply manifold 1 during the first air supply stroke, that is, the area downstream of the air supply from the area indicated by the two-dot chain line in FIG. It is set so that the nozzle tube 20 is located at the port side). In other words, the distance D2 from the connection portion P1 between the air supply collecting pipe 1 and the branch pipe 10 to the nozzle pipe 20 is set to be longer than the length D1 of the two-dot chain line region.

The mounting position of the injector 13 is as follows.
The volume (volume corresponding to the distance D2) in the air supply branch pipe 12 from the connection point P1 to the nozzle pipe 20 is set so as to be larger than the gas fuel volume V4 ejected in one operation. Have been.

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3. The nozzle pipe 20 has a plurality of injection ports 30 formed so as to radiate gas fuel radially from the nozzle axis O1 toward the entire surroundings. In addition, the distribution of the nozzles 30 is arranged more on the upstream side of the air supply (on the side of the air supply collecting pipe), whereby a large amount of gas fuel is ejected in opposition to the air supply flow, so that the gas fuel and the air supply are uniform. It is possible to perform a proper mixing.

FIG. 5 shows the exhaust gas temperature deviation between the cylinders (° C.).
FIG. 7 is a diagram showing a relationship between the volume ratio (gas fuel injection volume V4 / total volume V3 of the air supply branch pipe and the air supply port). Here, the exhaust temperature deviation temperature is a comparison between the exhaust temperature T of each cylinder detected by the exhaust temperature sensor 18 of each cylinder shown in FIG. 2 and the exhaust temperature Tma of the cylinder having the highest exhaust temperature.
The difference between x and the exhaust temperature Tmin of the cylinder having the lowest exhaust temperature is calculated. The smaller the exhaust temperature deviation temperature (Tmax-Tmin) is, the smaller the combustion disparity between the cylinders is. This indicates that uniform fuel supply is being performed.

According to experiments, the exhaust gas temperature deviation (Tmax-Tm)
In) is equal to or lower than 20 ° C., the uniformity of fuel supply between the cylinders is best maintained, and the exhaust temperature deviation is 35 ° C. to 4 ° C.
In the vicinity of 0 ° C., the operation can be performed to the extent that knocking does not occur. According to the graph of FIG. 5, in order to secure the exhaust gas temperature unevenness of 20 ° or less, the volume ratio V4
/ V3 needs to be about 35% or less, and the volume ratio needs to be about 50% or less in order to secure the exhaust gas temperature unevenness of about 35 ° C. to about 40 ° or less. It turns out that it is.

[0020]

A predetermined amount of gaseous fuel is injected from the injector 13 into the air supply branch pipe 12, and a predetermined amount of gas fuel is injected from the air supply manifold 1 into each air supply branch pipe 12 as shown in FIG. Is supplied.

In the air supply branch 12, the gas fuel and the air supply are mixed to form an air-fuel mixture, which is supplied into the combustion chamber 21 through the air supply port 15.

In the present embodiment, the volume V4 of the gas fuel injected into the air supply branch pipe 12 by one injection operation from the injector 13 is equal to the total volume V3 of the air supply branch pipe 12 and the air supply port 15. 35% or less and therefore the air supply branch 1
Outflow of gaseous fuel to the supply manifold 1 due to the lack of volume 2 is almost completely prevented, and in all cylinders, a predetermined amount of injected gaseous fuel can be supplied to the corresponding cylinder.

Further, the air-fuel mixture is subjected to a rectifying action in the process of passing through the curved extension pipe 11, and a uniform swirl flow can be generated in the combustion chamber.

[0024]

[Other Embodiments] (1) The illustrated embodiment may be an example applied to a multi-cylinder gas engine provided with a supercharger.
The present invention can also be applied to a multi-cylinder gas engine without a supercharger.

[0025]

As described above, according to the present invention, (1) In a multi-cylinder gas engine provided with an injector for each of the supply branch pipes 12 for each cylinder, the length of the supply branch pipe 12 is increased. By increasing the injector 13
The gas fuel ejected from the cylinder is prevented from flowing out to other cylinders through the air supply manifold 1, so that the gas fuel supply amount of each cylinder can be made uniform and the mixture can be made uniform thereby. Knocking or the like due to a combustion difference between cylinders can be prevented.

(2) By increasing the length of the air supply branch pipe 12, it is possible to lengthen the section for supplying air, thereby improving the rectifying effect of the air-fuel mixture flowing into each cylinder. A uniform swirl flow can be generated in the cylinder.

(3) If the injector 13 is arranged on the downstream side of the supply air from the supply air volume blown out from the air supply manifold 1 into the air supply branch pipe 12 at one time, Tube 1
In combination with the lengthening of the length 2, the gas fuel can be more reliably prevented from flowing out to the air supply manifold 1. Mixing uniformity is also improved, which also improves engine performance.

[Brief description of the drawings]

FIG. 1 is a front view of a multi-cylinder gas engine to which the present invention is applied.

FIG. 2 is a plan view of FIG.

FIG. 3 is an enlarged cross-sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a diagram showing a relationship between a volume ratio of a gas fuel, a volume ratio of a total volume of an air supply port and an air supply branch pipe, and an exhaust temperature uneven temperature.

FIG. 6 is a longitudinal sectional view showing an example of a conventional air supply branch pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air supply collecting pipe 2 Cylinder head 10 Branch pipe 11 Extension pipe 12 Air supply branch pipe 13 Injector 15 Air supply port 20 Nozzle pipe

Claims (2)

[Claims] An inlet end of a supply port of each cylinder is connected to a supply manifold via a supply branch pipe, and each supply branch pipe is provided with a gas fuel supply injector. In the supply pipe structure of a cylinder gas engine, the volume of gas fuel for one injection from the injector is approximately 以下 or less of the total volume of the supply branch pipe and the supply port in each cylinder. An air supply pipe structure for a multi-cylinder gas engine, wherein the length of the air supply branch pipe is increased. 2. An injector is disposed in a portion of a supply branch pipe downstream of the supply air from a volume area of the supply air blown out from the supply manifold into the supply branch pipe at one time. An air supply pipe structure for a multi-cylinder gas engine according to claim 1.