JPH09250402A - Fuel gas supply quantity control device for gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate malfanctioning operation whereby an excessive ratio of air is decreased at the time of hunching in engine speed. SOLUTION: Negative pressure V of intake passage 9 downstream from a throttle valve 8 is detected by a negative pressure detector 10, and flow control means 6 operates a flow controller 4 to perform its flow control operation, according to a detection value of the intake negative pressure V, thereby controlling the supply quantity of fuel gas, resulting in maintaining of the pressure V in the passage 9 to a set vale. When the engine speed is subjected to hunching, the negative pressure variation caused by the opening and closing operation of the throttle valve 8 and the negative pressure variation caused by increase and decrease of the engine speed are cancelled, and thereby control of valve opening degree in the flow controller 4 carried out according to the detection value of the pressure V is not so disturbed. Accordingly malfunctioning operation to cause generation of decreased excessive ratio of air can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel gas supply amount control device for reducing the amount of NOx produced in a gas engine by adjusting the air-fuel mixture ratio thinly during light load operation.

[0002]

[Precondition] The fuel gas supply amount control device for a gas engine of the present invention is intended for those having the following precondition as shown in FIG. 1 or 6, for example. The pressure of the fuel gas supplied from the fuel gas source (2) of the fuel supply system (1) of the gas engine is adjusted by the pressure adjuster (3) and the flow rate is adjusted by the flow rate adjuster (4), and the combustion chamber ( 5).

The flow rate controller (4) is constructed so that the flow rate control means (6) operates to adjust the flow rate. Governor the combustion air
The throttle valve (8) whose opening amount is adjusted in (7) is used to adjust the flow rate, and the flow is supplied to the combustion chamber (5) through the intake passage (9).

[0004]

2. Description of the Related Art In the above-described precondition, there is a conventional structure shown in FIG. 6 as a structure for reducing the amount of NOx generated by adjusting the air-fuel mixture ratio thinly during light load operation. , Which consists of: In an engine with a constant driving speed for driving a generator, the rotation sensor (23) detects the rotation speed of the crankshaft (22).

The flow rate control means (6) includes a rotation sensor (2
The deviation between the actual rotation speed detected by 3) and the set rotation speed is calculated, and the flow controller is adjusted until this rotation deviation reaches the set value.
By decreasing the flow rate of (4) to reduce the fuel gas supply amount, the excess air ratio of the air-fuel mixture is increased, and after the rotation deviation reaches the set value, the flow rate controller (4) is turned on. The flow rate is increased / decreased to maintain the rotation deviation at a set value.

For example, according to an experimental result, in order to reduce NOx to 100 ppm or less, when the engine rotational speed is 1500 rpm, the rotational deviation is set to 3
It has been reported to go to rpm. ("Development of air-fuel ratio control system for lean burn gas engine" Tokyo Gas Energy Technology Laboratory Technical Report No. 3 1993 54-
Page 63, Fig.7)

[0007]

In the above prior art, by adjusting the air-fuel mixture ratio thinly during light load operation,
It is excellent in that high output can be obtained by reducing the amount of NOx generated, reducing the fuel consumption rate, and returning the air-fuel mixture ratio to the rich side during high load operation.
However, there are the following problems.

(Ii). Accidentally reducing the excess air ratio during hunting of the rotational speed. During engine operation, disturbances such as sudden changes in load may disturb the rotational control of the engine by the governor, causing hunting of the rotational speed. is there. At the time of occurrence of this hunting, the rotation fluctuation range is set to the set value of the rotation deviation (3 rp in the previous example).
m), the flow rate controller (4) is erroneously operated to increase the flow rate to reduce the excess air ratio, and NO
A large amount of x is generated.

(B) A centrifugal governor or the like having a large speed fluctuation rate cannot be used Generally, the speed fluctuation rate of a practical centrifugal governor or pneumatic governor is about 3% even for a small value. The speed difference for 1500 rpm due to 3% of this speed fluctuation rate is 4
It is 5 rotations, and the set value of the rotation deviation (3 rp in the previous example)
m), the centrifugal governor or pneumatic governor can be used as an engine governor to reduce the amount of NOx produced by adjusting the air-fuel mixture ratio to a small value during light load operation. Cannot be used.

(C) In the case of an engine whose set rotational speed can be arbitrarily changed, it takes time and cost to obtain an appropriate set value of the rotational deviation for each set rotational speed. The set rotational speed can be arbitrarily changed. In the case of an engine, in order to keep the excess air ratio with respect to the load constant, it is necessary to gradually reduce the appropriate set value of the above rotation deviation as the set rotation speed becomes smaller. However, in order to obtain an appropriate set value of the above rotation deviation for each set rotation speed,
It requires a lot of experiments for each engine model, which takes a long time and is expensive.

An object of the present invention is to (a) eliminate an erroneous reduction of the excess air ratio during hunting of the rotation speed,
(B) A centrifugal governor with a large speed fluctuation rate can be used without any trouble, and (c) Even in the case of an engine that can arbitrarily change the set rotation speed, appropriate control settings can be set for each set rotation speed. There is no need to ask for a value.

[0012]

According to the present invention, in order to solve the above-mentioned problems in the above-mentioned premise, for example, as shown in FIGS. 1 to 4, the air-fuel mixture ratio is adjusted thinly during light load operation. Therefore, the following characteristic configuration is added as a configuration for reducing the amount of NOx generated.

Invention 1 1 to 4, the intake negative pressure (V) in the intake passage (9) is detected by the intake negative pressure detector (10).
It is configured to be detected by. The flow rate control means (6) is
Based on the detected value of the intake negative pressure (V) detected by the intake negative pressure detector (10), the flow rate adjuster (4) is operated to adjust the flow rate of the fuel gas, thereby adjusting the amount of fuel gas supplied. Intake negative pressure
The configuration is such that (V) is held at the set value (V ₀ ).

Invention 2. Referring to FIG. 1, in the configuration of the above invention 1, the fuel gas whose flow rate is adjusted by the flow rate adjuster (4) of the fuel supply system (1) of the gas engine is supplied to the gas mixer (11), and the fuel gas is supplied by the gas mixer (11). Is mixed with combustion air to form an air-fuel mixture, and the air-fuel mixture is supplied to the combustion chamber (5) through the throttle valve (8) and the intake passage (9).

○ Invention 3. See FIG. 4. In the configuration of the above invention 1, the fuel gas injection valve (12) is used as the flow rate controller (4) of the fuel supply system (1) of the gas engine.
Is used to directly inject the fuel gas whose flow rate is adjusted by the fuel gas injection valve (12) into the combustion chamber (5).

Invention 4. Refer to FIG. 5. In the configuration of the above-mentioned invention 1, 2 or 3, the power valve (13) is connected in parallel with the flow rate regulator (4) of the fuel supply system (1) of the gas engine, and the intake air of the intake passage (9) When the negative pressure (V) is equal to or lower than a predetermined value (V ₃ ) lower than the set value (V ₀ ),
The power valve (13) is configured to open.

[0017]

The present invention operates as follows. Invention 1, 2 or 3. 1 to FIG. 4 FIG. 2 is a curve diagram of excess air ratio-intake negative pressure change curve. During operation of the engine, the intake negative pressure (V) and the excess air ratio (λ) are held in the operation control target area A in this figure.

The intake negative pressure (V) is maintained at the set value (V ₀ ).
The upper limit value (v ₁ ) of the set value (V ₀ ) is, for example, −100 m.
mHg, and its lower limit value (v ₂ ) is set to −80 mmHg. The excess air ratio (λ) becomes larger as the load factor of the engine becomes smaller. For example, the excess air ratio (λ) is set to 1.25 when the load factor is 100%, and to 1.50 when the load factor is 0%.

FIG. 3 is a flow chart of the fuel flow rate control of the flow rate control means (6). By keeping the intake negative pressure (V) at the set value (V ₀ ), the excess air ratio (λ) corresponding to the load. Is controlled to a large value to maintain the lean combustion limit at each load. In the step (S1), a start command is issued by the engine start operation. Then, step (S
In 2), the standard fuel amount command is issued to increase the valve opening degree of the flow rate controller (4) to increase the supply amount of fuel gas and set the excess air ratio (λ) to 1.0. In step (S3), an engine start command is issued to start the engine.

When the engine is started, the governor (7) works to close the throttle valve (8) to an opening degree commensurate with the load, and the intake negative pressure (V) reaches the maximum value of each load factor in FIG. Become. The value of this intake negative pressure (V) is detected by the intake negative pressure detector (10) and transmitted to the flow rate control means (6). Then, the flow rate control means (6) issues a fuel reduction command in step (S4) to decrease the degree of valve opening of the flow rate controller (4) and reduce the flow rate of the fuel gas to increase the excess air ratio (λ). To go up. At this time, the governor (7) opens by opening the throttle valve (8),
Keep the actual engine speed at the set speed. Along with this, the intake negative pressure (V) is − along the curve (C) of the load factor in FIG.
Air excess ratio while decreasing toward 100 mmHg
Increase (λ).

At step (S5), the intake negative pressure (V) is -1.
Until the pressure decreases to 00 mmHg, the process returns to step (S4) and the valve opening degree of the flow rate controller (4) continues to be reduced. When the intake negative pressure (V) becomes -100 mmHg or less, step
Proceed to (S6). In step (S6), the intake negative pressure (V) is −
It is determined whether it is 80 mmHg or less. When it is more than that, the routine proceeds to step (S7), where a fuel amount fixing command is issued to fix the valve opening degree of the flow rate controller (4).
If it is less than that, the routine proceeds to step (S8), where a fuel increase command is issued to increase the valve opening degree of the flow rate controller (4).

Then, step (S7) or step
The process returns from (S8) to step (S5), and steps (S4) to (S8) are cycled through the above-described procedure. As a result, the intake negative pressure (V) is maintained at the set value (V ₀ ), the excess air ratio (λ) is controlled to a large value corresponding to the load, and the lean combustion limit at each load is maintained. . Specific features of the above operation will be described below.

(B). There is no malfunction in which the excess air ratio becomes small during hunting of the rotation speed. When the hunting occurs in the rotation speed during the operation of the engine, the following operation is performed. When the throttle valve (8) opens too much due to hunting and the engine speed increases, the intake negative pressure (V) decreases due to an increase in the opening of the throttle valve (8), and the engine speed increases. This cancels out the increase in the intake negative pressure (V), so that the intake negative pressure (V) does not fluctuate significantly.

On the contrary, when the throttle valve (8) is closed too much and the engine speed becomes low, the intake negative pressure (V)
Since the negative pressure increase amount due to the reduction of the valve opening degree and the negative pressure decrease amount due to the rotation speed decrease cancel each other, the intake negative pressure (V) does not fluctuate significantly. Therefore, even when hunting, the intake negative pressure
Since the control of the valve opening degree of the flow rate controller (4) based on the detected value of (V) is not disturbed so much, the malfunction that the excess air ratio (λ) becomes small can be eliminated. This allows
It is possible to prevent a large amount of NOx from being generated due to a decrease in the excess air ratio (λ).

(B). Can be used in centrifugal governors with large speed fluctuations In general, the speed fluctuations of practical centrifugal governors and pneumatic governors are often about 3-8%. Of 3
With a rotation head difference of about -8%, the control of the valve opening degree of the flow rate controller (4) based on the detected value of the intake negative pressure (V) is hardly disturbed. As a result, the centrifugal type governor and the pneumatic type governor can be used without any problem as an engine governor for reducing the amount of NOx produced by adjusting the air-fuel mixture ratio thinly during light load operation.

(C). In the case of an engine in which the set rotation speed can be arbitrarily changed, it is not necessary to change an appropriate set value of the intake negative pressure for each set rotation speed. In the case of an engine in which the set rotation speed can be arbitrarily changed. In order to keep the excess air ratio at a predetermined lean limit value corresponding to each load, the intake negative pressure (V) is maintained regardless of the difference in the set rotational speed.
It suffices that the set value (V ₀ ) of is set to a constant value. Therefore, in order to obtain the set value (V ₀ ) of the intake negative pressure (V), it suffices to obtain only one value, and it is not necessary to obtain a different value for each set rotational speed. It doesn't take long and the cost is low.

Invention 4. See FIG. 5 and FIG. 2 (d). When the engine is strongly started with a large torque, the intake negative pressure (V) in the intake passage (9) is lower than the set value (V ₀ ) by a predetermined value (V ₃ ) such as -70 m.
Since it is below mHg, the power valve (13) opens and the excess amount of fuel gas is increased by the increase in the supply amount of fuel gas.
(λ) becomes smaller and, for example, a rich mixture region of 1.0-1.2 shown in the rich mixing region (B) of FIG. 2 is obtained, and the engine can be strongly started with a large torque.

(E). Prevent the engine from stalling under a heavy load.
The throttle valve (8) is opened by the action of (8), and the intake negative pressure
(V) decreases from the set value (V ₀ ) to the predetermined value (V ₃ ) or less. Therefore, the power valve (13) is opened, and the excess air ratio (λ) is reduced by the increase in the supply amount of the fuel gas, and for example, 1.0− shown in the rich mixing region (B) of FIG. Since the engine starts to be driven strongly with a large torque due to the agricultural mixture of 1.2, it is possible to prevent the engine from stalling under a sudden load.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. ○ Embodiment 1 Refer to FIG. 1 to FIG. 3. The fuel gas supplied from the fuel gas source (2) of the fuel supply system (1) of the gas engine is pressure-adjusted by the pressure regulator (3) via the fuel inlet valve (26), The flow rate is adjusted by the flow rate controller (4) and supplied to the gas mixer (11). The pressure regulator (3) is composed of a zero governor and regulates the pressure of the fuel gas to atmospheric pressure.

The flow controller (4) is a main jet (4a).
And a bypass jet (4b) connected in parallel. The main jet (4a) consists of a fixed throttle nozzle. The bypass jet (4b) consists of a variable flow needle valve. Fuel gas and air cleaner (2
The combustion air purified in 7) is mixed to form a mixture. This air-fuel mixture is passed through a throttle valve (8) and an intake passage (9) whose opening is controlled by a governor (7) and then passed through a combustion chamber (5).
It is configured to supply to. As the governor (7), a centrifugal governor, a pneumatic governor or an electronic governor is used.

By-pass jet (4b) of flow controller (4)
Is configured so that the flow rate control means (6) composed of a microcomputer is used to adjust the flow rate. Intake negative pressure in the intake passage (9)
(V) is detected by the intake negative pressure detector (10).
The flow rate control means (6) controls the flow rate controller (4) to adjust the flow rate of the fuel gas based on the detected value of the intake negative pressure (V) detected by the intake negative pressure detector (10). By doing so, the intake negative pressure (V) of the intake passage (9) is maintained at the set value (V ₀ ).

As shown in FIG. 2, the set value (V ₀ ) of the intake negative pressure (V) has an upper limit value (v ₁ ) of −100 mmH, for example.
g, and the lower limit value (v ₂ ) thereof is set to −80 mmHg.
The excess air ratio (λ) becomes larger as the load factor of the engine becomes smaller. For example, when the load factor is 100%, the excess air factor (λ) is 1.25, and when it is 0%, it is 1.5.
It is set to 0.

Second Embodiment Referring to FIG. 4, the second embodiment shown in FIG. 4 is the same as the first embodiment shown in FIG. 1 except that the structure for supplying the fuel gas is changed as follows. Gas engine fuel supply system
A fuel gas injection valve (12) is used as the flow rate controller (4) of (1). Fuel gas source for gas engine fuel supply system (1)
The fuel gas supplied from (2) is pressurized by the compressor (31) through the fuel inlet valve (26), the pressure is adjusted by the pressure regulator (3), and the flow rate is adjusted by the fuel gas injection valve (12). The combustion chamber
It is configured to directly inject into the inner part of the sub chamber (5a) of (5).

The pressure regulator (3) regulates the pressure of the fuel gas to a predetermined positive pressure higher than atmospheric pressure. The spark plug (32) faces the inner part of the sub chamber (5a). The ignition timing setting cam (35) is fixed to the valve camshaft (34) that works with the crankshaft (33), and the electromagnetic pulse sensor (36) changes the rotation angle of this cam (35) to the igniter (37). Tell the spark plug (3
2) is ignited at a predetermined ignition timing. The pulse sensor (36) also transmits the rotation angle of the cam (35) to the fuel flow rate control means (6) so that the fuel injection timing of the fuel gas injection valve (12) is changed from the intake stroke to the beginning of the compression stroke. Is set to.

Third Embodiment Refer to FIG. 5. In the third embodiment shown in FIG. 5, the configuration for supplying the fuel gas is modified as follows in the configuration of the first embodiment shown in FIG. Gas engine fuel supply system
The flow rate controller (4) of (1) consists only of a variable flow rate needle valve. The valve box (4c) of the flow rate regulator (4) is screw-fitted (41) to the body (3c) of the pressure regulator (3) composed of zero governor.
Fixed directly by. A power valve (13) is connected in parallel with the flow rate controller (4). Intake negative pressure in intake passage (9)
The power valve (13) is configured to open when (V) is less than or equal to a predetermined value (V ₃ ) lower than the set value (V ₀ ). The predetermined value (V ₃₎ is set to -70MmHg.

[0036]

The present invention is configured and operated as described above, and has the following effects. (B). There is no malfunction in which the excess air ratio becomes smaller during rotation speed hunting. When the rotation speed hunts during engine operation, the following actions occur. When the throttle valve (8) opens too much due to hunting and the engine speed increases, the intake negative pressure (V) decreases due to an increase in the opening of the throttle valve (8), and the engine speed increases. This cancels out the increase in the intake negative pressure (V), so that the intake negative pressure (V) does not fluctuate significantly.

On the contrary, even when the throttle valve (8) is closed too much and the engine speed becomes low, the intake negative pressure (V)
Since the negative pressure increase amount due to the reduction of the valve opening degree and the negative pressure decrease amount due to the rotation speed decrease cancel each other, the intake negative pressure (V) does not fluctuate significantly. Therefore, even when hunting, the intake negative pressure
Since the control of the valve opening degree of the flow rate controller (4) based on the detected value of (V) is not disturbed so much, the malfunction that the excess air ratio (λ) becomes small can be eliminated. This allows
It is possible to prevent a large amount of NOx from being generated due to a decrease in the excess air ratio (λ).

(B). Centrifugal governor with a large speed fluctuation rate can be used. Generally, the speed fluctuation rate of a practical centrifugal governor or pneumatic governor is about 3-8%. Of 3
With a rotation head difference of about -8%, the control of the valve opening degree of the flow rate controller (4) based on the detected value of the intake negative pressure (V) is hardly disturbed. As a result, the centrifugal type governor and the pneumatic type governor can be used without any problem as an engine governor for reducing the amount of NOx produced by adjusting the air-fuel mixture ratio thinly during light load operation.

(C). In the case of an engine in which the set rotation speed can be arbitrarily changed, it is not necessary to change an appropriate set value of the intake negative pressure for each set rotation speed. In the case of an engine in which the set rotation speed can be arbitrarily changed. In order to keep the excess air ratio at a predetermined lean limit value corresponding to each load, the intake negative pressure (V) is maintained regardless of the difference in the set rotational speed.
It suffices that the set value (V ₀ ) of is set to a constant value. Therefore, in order to obtain the set value (V ₀ ) of the intake negative pressure (V), it suffices to obtain only one value, and it is not necessary to obtain a different value for each set rotational speed. It doesn't take long and the cost is low.

Invention 4. See FIG. 5 and FIG. 2 (d). When the engine is strongly started with a large torque, the intake negative pressure (V) in the intake passage (9) is lower than the set value (V ₀ ) by a predetermined value (V ₃ ) such as -70 m.
Since it is below mHg, the power valve (13) opens and the excess amount of fuel gas is increased by the increase in the supply amount of fuel gas.
(λ) becomes smaller and, for example, a rich mixture region of 1.0-1.2 shown in the rich mixing region (B) of FIG. 2 is obtained, and the engine can be strongly started with a large torque.

(E). Prevent the engine from stalling under a heavy load.
The throttle valve (8) is opened by the action of (8), and the intake negative pressure
(V) decreases from the set value (V ₀ ) to the predetermined value (V ₃ ) or less. Therefore, the power valve (13) is opened, and the excess air ratio (λ) is reduced by the increase in the supply amount of the fuel gas, and for example, 1.0− shown in the rich mixing region (B) of FIG. Since the engine starts to be driven strongly with a large torque due to the agricultural mixture of 1.2, it is possible to prevent the engine from stalling under a sudden load.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a fuel gas supply amount control device for a gas engine showing a first embodiment of the present invention.

FIG. 2 is an excess air ratio-intake negative pressure change curve showing a fuel gas supply amount control region.

FIG. 3 is a flowchart for controlling a fuel gas supply amount.

FIG. 4 is a conceptual diagram of a fuel gas supply amount control device for a gas engine showing a second embodiment.

FIG. 5 is a conceptual diagram of a fuel gas supply amount control device for a gas engine showing a third embodiment.

FIG. 6 is a conceptual diagram of a fuel gas supply amount control device for a gas engine showing a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel supply system, 2 ... Fuel gas source, 3 ... Pressure regulator, 4 ... Flow controller, 5 ... Combustion chamber, 6 ... Flow control means, 7 ... Governor, 8 ... Throttle valve, 9 ... Intake passage, 10 ... Intake negative pressure detector, 11 ... Gas mixer, 1
2 ... fuel gas injection valve, 13 ... power valves, V ... intake negative pressure, V ₀ ... setting value, V ₃ ... predetermined value.

Claims (4)

[Claims] 1. A pressure regulator (3) for supplying fuel gas supplied from a fuel gas source (2) of a fuel supply system (1) of a gas engine.
Adjust the pressure with, adjust the flow with the flow controller (4), and
The throttle valve is configured to supply to (5), the flow rate controller (4) is configured to control the flow rate by the flow rate control means (6), and the opening amount of combustion air is controlled by the governor (7).
Adjust the flow rate with (8), and through the intake passage (9), the combustion chamber (5)
A fuel gas supply amount control device for a gas engine configured to supply the intake negative pressure (V) in the intake passage (9) to an intake negative pressure detector (10).
The flow rate control means (6) operates the flow rate controller (4) based on the detected value of the intake negative pressure (V) detected by the intake negative pressure detector (10). The fuel gas supply amount of the gas engine is characterized in that the intake negative pressure (V) of the intake passage (9) is maintained at the set value (V ₀ ) by adjusting the fuel gas supply amount by performing the adjustment. Control device. 2. A gas mixer (1) for supplying the fuel gas whose flow rate is adjusted by the flow rate adjuster (4) of the fuel supply system (1) of the gas engine.
1), and the gas mixer (11) mixes the fuel gas and the combustion air to form an air-fuel mixture. The air-fuel mixture is passed through the throttle valve (8) and the intake passage (9) and the combustion chamber (5 ) Is supplied to the fuel gas supply amount control device for the gas engine according to claim 1. 3. A fuel gas injection valve (12) is used as the flow rate controller (4) of a fuel supply system (1) of a gas engine, and the fuel gas whose flow rate is adjusted by the fuel gas injection valve (12) is used in a combustion chamber.
The fuel gas supply amount control device for a gas engine according to claim 1, wherein the fuel gas supply amount control device is configured to inject directly to (5). 4. A power valve (13) is connected in parallel with the flow rate controller (4) of a fuel supply system (1) of a gas engine, and an intake negative pressure (V) of an intake passage (9) is the set value. The fuel for a gas engine according to claim 1, 2 or 3, wherein the power valve (13) is configured to open when the value is less than a predetermined value (V ₃ ) lower than (V ₀ ). Gas supply control device.