JPH05263675A - Method and device for controlling operation of gas engine - Google Patents

Abstract

PURPOSE:To increase the air ratio of a lean combustive gas engine as much as possible and promote reduction of NOx without bringing about unstableness of combustion by sensing the output of a generator connected with the engine, and decreasing the air ratio when the sensed output exceeds a specified valve. CONSTITUTION:A fuel gas supply passage 12 and air supply passage 14 are installed on the suction side of a lean combustive gas engine 10 and converged by a mixer 16. A bypass 20 branched frog the supply passage 12 is put in communication with a mixture gas passage 18 downstream of this mixer 16 and is fitted with a bypass valve 22. With the gas engine 10 also a generator 24 is connected. The power generated by this generator 24 and its amplitude are sensed by a generator control device 26. On the basis of the sensing signal thus emitted, a stabilization control device 28 controls a bypass valve 22, etc. That is when the amplitude of the power exceeds a specified level, the opening of the bypass valve 22 is increased for decreasing the air ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to operation control of a gas engine, and more particularly to a method and apparatus for controlling an air ratio in a lean burn gas engine connected with a generator.

[0002]

2. Description of the Related Art In response to the recent growing awareness of environmental issues, nitrogen oxides (N
The demand for reducing the Ox) concentration has become very strict.
Here, it is known that NOx concentration decreases as the ratio of gas as fuel in the mixture of air and gas supplied to the engine decreases, or as the air ratio increases. The lean burn gas engine was proposed based on such a fact, and its air ratio is extremely high as compared with a normal gas engine.

However, if the air ratio is increased (the equivalence ratio is decreased), the combustion stability in the gas engine deteriorates, which is inconvenient. Therefore, in the lean burn gas engine, it is desired to increase the air ratio within a range where the combustion state is stable or within a range where the combustion stability limit is not exceeded. On the other hand, in the conventional lean burn gas engine, map control was performed by a computer.

[0004]

However, the map control by the computer cannot always meet the demand of increasing the air ratio as much as possible without exceeding the limit of combustion stability. That is, the map control by a computer has a problem that it is ineffective against disturbances such as changes in gas composition and changes in operating conditions, and in addition, the cost required for introduction is very high.

Further, it is considered to introduce a technique used for controlling the operation of an engine of an automobile or the like, for example, a control using a wide-range oxygen sensor or a control using a rotation speed fluctuation detection type combustion stability detection device for detecting uneven rotation. Be done. However, with the engine and gas engine for automobiles, the usage conditions,
Since the characteristics required and regulations to be cleared are too different, it is currently not possible to apply the technology used for the operation control of the engine of automobiles etc. to the operation control of the lean burn gas engine. Has not been put into practical use.

The present invention has been proposed in view of the above problems of the prior art, and in a lean burn gas engine,
An object of the present invention is to provide an operation control method and apparatus for a gas engine that enables operation control such that combustion is stabilized and the air ratio is increased as much as possible.

[0007]

The inventor has found that the engine rotation is limited to the case of a gas engine capable of so-called "system cooperation" in which the generated power of a generator connected to the gas engine and the external power are synchronized. We focused on the phenomenon that combustion stability can be determined by monitoring the power (current) of the generator connected to the gas engine without detecting the number.
Then, when the combustion state of the engine is unstable, attention was paid to the fact that the amplitude of the electric power becomes large.

The operation control method of the gas engine of the present invention comprises:
A step of detecting the output of a generator connected to the lean burn gas engine, and a step of reducing the air ratio of the lean burn gas engine when the amplitude of the output of the generator exceeds a predetermined value,
Includes and.

Further, the operation control device for the gas engine of the present invention detects the output of the generator connected to the lean burn gas engine, and detects when the amplitude of the output of the generator exceeds a predetermined value. Judgment means for making a judgment to reduce the air ratio of the lean burn gas engine, and an air ratio change that makes the air ratio of the lean burn gas engine smaller in response to a judgment made by the judging means to make the air ratio smaller. Means, and.

In the practice of the present invention, the amplitude of the generator output above a predetermined value is 10% of the set power value (current value) in the case of a single-chamber combustion type gas engine, and that of the auxiliary chamber combustion type. In the case of a gas engine, it is preferable to set it to 5% of the set power value (current value).

Further, as a concrete method for executing the step of reducing the air ratio, the opening degree of the bypass valve on the gas supply side is increased, the gas pressure is controlled to be increased, or the engine output is increased. There are various conceivable cases such as decreasing the number, and the specific method is not particularly limited in the present invention.

Further, as the above-mentioned detection means, most commercially available power generation gas engines have an engine control panel and a generator panel so that the amount of electric power (current amount) can be observed. You can use it. As the determining means, it is preferable to adopt a control device provided in combination with the engine control panel and the generator panel.

In implementing the present invention, if it is desired to reduce the NOx concentration, the power generated by the generator (current generated)
It is possible to perform control so that the air ratio automatically increases as long as the amplitude of does not exceed a predetermined range. On the other hand, when targeting gas composition fluctuations, it is necessary to make the air ratio not larger than the set value.

[0014]

As described above, since the power generated by the generator connected to the gas engine is a physical quantity that directly indicates the combustion stability of the gas engine, in the present invention, the power generated by the generator (current generated) is generated. ) Is observed, and if the air ratio is increased as long as it does not exceed a predetermined range, the gas engine can be operated with a high air ratio without destabilizing the combustion. That is, when operating the gas engine, the air ratio is increased until the amplitude of the generated power (generated current) of the generator connected to the gas engine exceeds the predetermined range, and if the amplitude exceeds the predetermined range. Lower the air ratio.

According to the present invention, the NOx concentration in the exhaust gas can be reduced by increasing the air ratio as much as possible. In addition, since the combustion of the gas engine is prevented from becoming unstable, the stability of the combustion of the gas engine is ensured in areas where there are many disturbance factors of the combustion of the gas engine, such as changes in the gas composition, and troubles are prevented. Can be wiped out.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a gas engine and a generator embodying the present invention. A fuel gas supply passage 12 and an air supply passage 14 are provided on the intake side of the lean burn gas engine 10, and the passages 12 and 14 are joined by a mixer 16. A bypass passage 20 branched from the fuel gas supply passage 12 is joined to the mixture passage 18 on the downstream side of the mixer 16, and a bypass valve 22 is provided in the bypass passage 20.

The gas engine 10 is connected to a generator 24, and the generator 24 is provided with a generator control device 26 which is means for detecting the generated electric power and its amplitude. The generator control device 26 monitors the generated electric power,
The output value, output waveform, and output amplitude (see FIGS. 3 and 4) are detected and a signal is generated. The detection signal of the generator control device 26 is input to the stability control device 28, and the control signal of the stability control device 28 is output to the bypass valve 22 or the generator control device 26.

Next, one mode of the control according to the present invention will be described with reference to FIGS.

When the operation of the gas engine 10 is started, first, the air-fuel ratio or the air ratio of the fuel gas and the air supplied to the gas engine is set (FIG. 2, step S).
1). Here, since the present invention is applied to a lean-burn gas engine, the air ratio is, for example, 1.4 to 1.6 for a single-chamber combustion type gas engine, and a sub-chamber combustion type gas engine. If so, for example, it is set to 2.0 to 2.2. At the same time, the allowable value of the amplitude of the electric power generated by the generator 24 is set (step S1). As is clear by comparing FIG. 4 showing the power waveform in the stable combustion state with FIG. 3 showing the power waveform in the unstable combustion state, the power amplitude increases when the combustion state becomes unstable.
Therefore, an allowable value is set such that if the amplitude becomes larger than this, adverse effects will occur, and the allowable value will be used as a threshold value. If the amplitude exceeds it, it is determined that the combustion state is unstable. In other words, the setting of the allowable value of the power amplitude is nothing but the setting of the threshold value.

When the setting is completed in step S1, the gas engine 10 is operated and power generation is started. And the generator 24
It is judged whether the output of (1) shows a characteristic that the amplitude is small as shown in FIG. 4 or the amplitude is relatively large as shown in FIG. Specifically, it is determined whether the output amplitude of the generator 24 detected by the generator control device 26 is larger (unstable combustion) or smaller (stable combustion) than the allowable value set in step S1 (step S2). ).

When the output amplitude of the generator 24 is smaller than the allowable value (YES in step S2), the combustion state is stable, so the operation is continued (step S3), and the stability control device 28 causes the bypass valve to operate. A control signal is sent to 22 to reduce the opening to reduce the fuel gas supply amount and increase the air ratio (step S4). As a result, the gas engine 10 is operated in combustion with a higher air ratio.

On the other hand, if the output amplitude of the generator 24 is larger than the permissible value (NO in step S2), it means that the air ratio is too large and combustion is unstable, so stability control is performed. The device 28 sends a control signal to the bypass valve 22 to increase the opening to increase the fuel gas supply amount,
The air ratio is reduced (step S5).

By repeating the above procedure, the air ratio can be increased as much as possible within the range where the combustion state is stable.

[0025]

The effects of the present invention are listed below.

(1) The operation can be performed with the air ratio as high as possible without destabilizing the combustion of the gas engine.

(2) The NOx concentration of exhaust gas can be reduced.

(3) Various inconveniences caused by the unstable combustion of the gas engine are prevented.

(4) It is possible to eliminate the trouble by ensuring the stability of the combustion of the gas engine in the area where the disturbance factors of the combustion of the gas engine frequently occur such as the fluctuation of the gas composition.

(5) Practical application is easy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an arrangement of a gas engine and a generator embodying the present invention.

FIG. 2 is a flow chart showing an aspect of control according to the present invention.

FIG. 3 is a power characteristic diagram of a generator when combustion is unstable.

FIG. 4 is a power characteristic diagram of a generator when combustion is stable.

[Explanation of Codes] 10 ... Lean combustion gas engine 12 ... Fuel gas supply passage 14 ... Air supply passage 16 ... Mixer 18 ... Mixture passage 18 20 ... Bypass passage 22 ... -Bypass valve 24 ... Generator 26 ... Generator control device 28 ... Stability control device

Claims (2)

[Claims] 1. A step of detecting an output of a generator connected to a lean burn gas engine, and a step of reducing an air ratio of the lean burn gas engine when an amplitude of an output of the generator exceeds a predetermined value, A method of controlling the operation of a gas engine, comprising: 2. A detecting means for detecting the output of a generator connected to the lean burn gas engine, and a means for reducing the air ratio of the lean burn gas engine when the amplitude of the output of the generator exceeds a predetermined value. The gas ratio changing means for reducing the air ratio of the lean burn gas engine in response to the determination means for reducing the air ratio. Engine operation control device.