JPH05118255A - Air and fuel mixing device for gas engine - Google Patents

Abstract

PURPOSE:To prevent a maximum output from being reduced so much compared with that before the regulations are intensified while maintaining the incidence of NOx at a low reference value after the regulations are intensified when the engine is operated with low output or medium output. CONSTITUTION:An intake valve 8 which is operated based on intake negative pressures on the downstream side of a throttle valve 2 is connected to a gas supply passage 6 on the upstream side of the throttle valve 2 so that air can be entered. In a high negative pressure operating state where negative pressures are high, the amount of opening of the intake valve 8 becomes large to increase the amount of air entering the gas supply passage 6. Besides, in a low negative pressure operating state, the amount of opening of the intake valve 8 becomes small to decrease the amount of air entering the gas supply passage. Thus, when the engine is operated with low or medium output, the incidence of NOx is reduced below a reference value, and when the engine is operated with maximum output, the value of maximum output is almost not reduced compared with that before the regulations are intensified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel mixing device for a gas engine.

[0002]

2. Description of the Related Art The basic structure of an air-fuel mixing device for a gas engine is conventionally constructed as shown in FIG.
That is, a venturi pipe 3 is continuously provided on the upstream side of a mixer main pipe 1 having a throttle valve 2, a plurality of fuel discharge pitot ports 4 are exposed to an inner wall 3a of the venturi pipe 3, and each pitot pipe 3 is surrounded by each pitot pipe 3. An annular fuel supply port 5 that communicates with the port 4 is formed, and a fuel gas G supply pipe 6 is formed in the fuel supply port 5.
It is configured by connecting.

By the way, engine exhaust gas NO _{x is} coming soon.
Regulations will be tightened. That is, in FIG. 2, the reference value of NO _X is lowered from L ₀ to L ₁ . The NO _x emission amount needs to be changed from the graph B ₀ before the regulation is tightened to the graph B ₁ after the regulation is tightened in order to keep the rated output K ₀ to be equal to or less than the reference value L ₁ . There is a lean burn method as a method for obtaining this graph B ₁ . That is, the excess air ratio is set to a low value γ
_The value should be changed from ₀ to a higher value γ ₁ after tightening regulations. In order to obtain the excess air ratio γ ₁ after the regulation is tightened, in the conventional technique, in the basic structure of FIG. 3, the passage cross-sectional area of the fuel discharge pitot port 4 is narrowed down from the value before the regulation is tightened to a smaller value. I was there.

[0004]

In the above-mentioned conventional technique, the passage cross-sectional area of the pitot port 4 is set to be narrow, which causes the following problems. The excess air ratio is kept constant at a high value γ ₁ (graph A ₁ ) after tightening the regulation over the entire range from the minimum output Kmin to the maximum output Kmax. For this reason, the maximum output of the engine is reduced as compared with the case before the regulation is strengthened by the amount that the excess air ratio is increased from γ ₀ to γ ₁ . The present invention has been made in consideration of such circumstances, and at the time of low-power or medium-power operation, the maximum output is strengthened while the NO _X generation rate is maintained at the low reference value L ₁ after the restriction is strengthened. It is a technical issue to prevent the deterioration so much compared to the previous case.

[0005]

The present invention is configured as follows to solve the above problems. That is, in the mixer main pipe 1, the fuel discharge pitot port 4 is opened in the upstream venturi portion 3 of the throttle valve 2, and the gas supply passage 6 of the fuel gas G is connected to the pitot port 4 of the gas engine. In the air-fuel mixing device, an air supply valve 8 that operates based on the intake negative pressure on the downstream side of the throttle valve 2 is connected to the gas supply passage 6 so that air can be mixed therein, and a high negative pressure operation with a high intake negative pressure is performed. In the state, the opening amount of the air supply valve 8 becomes large and the amount of air mixed into the gas supply path 6 increases, whereas in the low negative pressure operating state, the opening amount becomes small. It is characterized in that the air mixing amount is reduced.

[0006]

[Operation] The present invention operates as follows. During low or medium output operation of the engine, the throttle valve 2 is throttled, the intake negative pressure is increased, the opening amount of the intake valve 8 is increased, and the amount of air mixed into the gas supply passage 6 is increased. .. As a result, as shown in the graph A ₂ in FIG. 2, the excess air ratio becomes a high value γ ₁ after the regulation is strengthened, and as shown in the graph B ₂ , the NO _X generation rate is the low reference value after the regulation is strengthened. It becomes lower than L ₁ .

During the maximum output operation of the engine, the throttle valve 2 is fully opened, the intake negative pressure is reduced, the opening amount of the intake valve 8 is reduced, and the amount of air mixed in the gas supply passage 6 is reduced. .. As a result, as shown in the graph A ₂ , the excess air ratio decreases from the high value γ ₁ after the tightening of regulations,
It becomes a low value γ ₀ before the regulation is tightened or a value close to this value, and the maximum output value is hardly reduced as compared with the case before the regulation is tightened.

[0008]

Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 is a sectional view of an air-fuel mixing device for a gas engine according to an embodiment of the present invention. In this embodiment, the mixer main pipe 1 having a throttle valve 2, a venturi pipe 3 connected upstream of the mixer main pipe 1, a fuel gas G supply pipe 6 connected to the venturi pipe 3, and an engine And an air supply valve 8 that operates at negative intake pressure.

A plurality of fuel discharge pitot ports 4 are opened in the inner wall 3a of the venturi pipe 3, and the venturi pipe 3 is communicated with the pitot ports 4 around the venturi pipe 3 to form one of the fuel gas supply paths 6. A ring-shaped fuel supply port 5 forming a part is formed, and a fuel supply pipe 6a is connected to the fuel supply port 5. Further, between the fuel supply port 5 of the Venturi pipe 3 and the downstream side of the throttle valve 2, the air supply valve 8 which is operated by the intake negative pressure of the engine is attached.

The air supply valve 8 has a pair of case bodies 10a and 10b which form a diaphragm working chamber 11 therein, a diaphragm 12 which partitions the diaphragm working chamber 11 into a primary working chamber 11a and a secondary working chamber 11b. Diaphragm 1
2, the valve body 13 fixed to the central part of 2 and the diaphragm 12
And an urging spring 17 for urging the valve element 13 toward the primary working chamber 11a side, and the air supply inlet 14 of the primary working chamber 11a.
Is connected to the atmosphere, the air supply outlet 15 is connected to the fuel supply port 5 of the Venturi pipe 3, and the communication opening 16 of the secondary working chamber 11b is connected to the downstream side of the throttle valve 2.

According to the air supply valve 8, the throttle valve 2 is narrowed down and the intake negative pressure is increased during the low or medium output operation of the engine, and the pressure in the primary working chamber 11a is applied to the pressing bias spring 17. Overcome and fully open the air supply outlet 15.
As a result, as shown in the graph A ₂ in FIG. 2, the excess air ratio becomes a high value γ ₁ after the regulation is strengthened, and as shown in the graph B ₂ , the NO _X generation rate is the low reference value after the regulation is strengthened. It becomes lower than L ₁ .

On the other hand, when the engine is operating at the rated output K ₀ or high output, the intake negative pressure becomes low, and the pressing bias spring 17
Presses the valve body 13 to narrow down the air supply outlet 15 of the primary working chamber 11a, and the amount of air mixed into the gas supply passage 6 decreases. As a result, at the time of maximum output operation, graph A
_As shown in Fig. ₂ , the excess air ratio decreases from the high value γ ₁ after stricter regulation and becomes the low value γ ₀ before stricter regulation or a value close to this, and the maximum output value is In comparison, it hardly decreases. The present invention is not limited to the above-described embodiment, and for example, the intake negative pressure may be detected by the negative pressure sensor, and the air supply valve may be operated via the electric actuator based on the detection signal. Well, it does not require many words that it can be implemented with appropriate changes.

[0013]

According to the present invention, the intake valve 8 operating on the downstream side of the intake valve negative pressure of the throttle valve 2 is connected to the gas supply path 6 so that air can be mixed therein, and the intake negative pressure is high. In the operating state, the amount of air mixed into the gas supply passage 6 is increased, while in the low negative pressure operating state, the amount of air mixed is reduced, so that during low output or medium output operation. , NO _x can be maintained at a low reference value L ₁ after the regulation is reinforced, but the maximum output can be prevented from being lowered so much as compared with the case before the regulation is reinforced.

[Brief description of drawings]

FIG. 1 is a sectional view of an air-fuel mixing device for a gas engine according to an embodiment of the present invention.

FIG. 2 is a graph illustrating an NO _X generation rate and an excess air ratio with respect to an engine output.

FIG. 3 is a cross-sectional view of an air-fuel mixing device for a gas engine according to a conventional technique.

[Explanation of symbols]

1 ... Mixer main pipe, 2 ... Throttle valve, 3 ... Venturi part (venturi pipe), 4 ... Fuel discharge pitot port, 6 ... Fuel gas supply passage, 8 ...
Air supply valve, G ... Fuel gas.

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[Procedure amendment]

[Submission date] October 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (1)

[Claims] 1. A throttle valve (2) in a mixer main (1).
Pitot port (4) for fuel discharge in the upstream venturi section (3)
In the air-fuel mixing device of the gas engine, which is configured by connecting the gas supply passage (6) for the fuel gas (G) to the pitot opening (4), the intake air intake downstream of the throttle valve (2) is The air supply valve (8) that operates based on the pressure is connected to the gas supply passage (6) so that air can be mixed, and the air supply valve (8) is operated in a high negative pressure operation state where the intake negative pressure is high.
While the valve opening amount of (8) becomes large and the amount of air mixed into the gas supply path (6) increases, the valve opening amount becomes small in the low negative pressure operation state and An air-fuel mixing device for a gas engine, which is configured so as to reduce the amount of mixing.