JP2768838B2 - Gas engine combustion control system for power generation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas for power generation combined with a turbocharger which is coaxial with a turbine driven by exhaust gas of an engine and which sends air mixed with gas fuel by a compressor which rotates integrally therewith. The present invention relates to a combustion control device for an engine.

[0002]

2. Description of the Related Art Conventionally, a gas engine power generation system equipped with a combustion control device shown in FIG. 10 is known, and comprises a turbine 1 and a compressor 2 coaxially therewith and integrally rotating.
The generator 5 is driven by a gas engine 4 combined with a turbocharger 3 comprising An exhaust gas supply passage 6 and an exhaust gas discharge passage 7 are provided in the turbine 1.
The exhaust gas supply passage 6 is connected to an exhaust gas outlet of the gas engine 4, and the exhaust gas supply passage 6 and the exhaust gas discharge passage 7 are directly connected by a bypass passage 9 having a bypass valve 8. . The compressor 2 is connected to a compressor suction passage 11 and an engine air supply passage 12 having a filter 10 at an inlet. Further, a load detector 13 that detects an output of the generator 5 at an output section of the generator 5 and outputs a detected value, and detects an air supply pressure in the engine air supply passage 12 while receiving the load signal, Based on the difference between the set value of the supply pressure corresponding to the value of the load signal and the detected supply pressure, a pressure that outputs an operation signal to the bypass valve 9 to operate the bypass valve 9 in a direction to cancel the difference. A controller 14 is provided.

[0003] The compressor 2 is rotated by the turbine 1 driven by the exhaust gas of the gas engine 4. Further, the compressor 2 compresses air sucked from a compressor suction passage 11 through a filter 10, and compresses compressed air mixed with gas fuel, for example, propane gas and city gas, from an engine supply passage 12 to the gas engine 4. To operate the gas engine 4 and generate electric power by the generator 5 rotating therewith. Further, the combustion control device including the bypass valve 8, the bypass flow path 9, the load detector 13, and the pressure controller 14 opens and closes the bypass valve 8 so that the supply pressure becomes equal to the supply pressure set value. The exhaust gas from the gas engine 4 is appropriately bypassed, the rotation speed of the turbine 1 is adjusted, the air / fuel ratio is kept constant, the gas engine 4 is not misfired, the exhaust gas temperature and the N in the exhaust gas are reduced.
An abnormal increase in ox concentration is prevented.

[0004]

The above-mentioned conventional combustion control apparatus for a power generating gas engine has a pressure so as to make the detected supply air pressure equal to a supply air pressure set value corresponding one-to-one to the value of the load signal. The controller 14, the bypass valve 8, and the bypass channel 9 are provided. Therefore, filter 1
0, the outside air temperature rises, etc., the air supply amount decreases substantially, and the temperature of the exhaust gas from the gas engine 4 rises,
This may damage the turbine 1 and raise the problem of increasing the concentration of Nox. In order to prevent this, it is conceivable to increase the set value of the supply pressure. However, doing so has a problem in that stable combustion and fuel efficiency of the gas engine 4 are adversely affected. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has a good fuel efficiency without causing a gas engine to misfire, and is capable of preventing an abnormal increase in exhaust gas temperature and NOx concentration in exhaust gas. It is intended to provide a combustion control device for a gas engine.

[0005]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide air which is coaxial with a turbine driven by engine exhaust gas and mixed with gaseous fuel by a compressor which rotates integrally therewith. In a combustion control device for a gas engine for power generation combined with a turbocharger that sends out a gas, a bypass flow path that directly connects an exhaust gas supply flow path of the turbine to an exhaust gas discharge flow path via a bypass valve, A temperature controller that detects an exhaust gas temperature and outputs an air supply pressure setting signal indicating an engine air supply pressure that produces an air / fuel ratio corresponding to the detected temperature, and an output of a generator driven by the gas engine. A load detector that detects and outputs the detected output as a load signal, and detects the supply pressure in the engine supply passage from the compressor to the gas engine On the other hand, when the supply air pressure setting signal and the load signal are received and the pressure value indicated by the supply air pressure setting signal is larger than the allowable upper limit of the engine air supply pressure set value with respect to the engine load, the allowable upper limit is set to: When the engine supply pressure set value is smaller than the allowable lower limit value, the allowable lower limit value is set as the engine supply pressure setting value in other cases. A pressure controller for outputting an operation signal for operating the bypass valve in a direction to cancel the difference based on a difference between the detected supply pressure and the supply pressure in the air flow path is provided.

Further, a second invention is a power generating gas engine which is coaxial with a turbine driven by engine exhaust gas and which is combined with a turbocharger for sending air mixed with gas fuel by a compressor which rotates integrally therewith. In the combustion control device, the exhaust gas supply flow path of the turbine is directly connected to the exhaust gas discharge flow path via a bypass valve, and the temperature of the exhaust gas in the exhaust gas supply flow path is detected to correspond to the detected temperature. A temperature controller that outputs an air supply pressure setting signal that indicates an engine air supply pressure that generates an air / fuel ratio, and a load that detects an output of a generator driven by the gas engine and outputs a detected output as a load signal. A detector for detecting a supply pressure and a supply temperature in an engine supply passage from the compressor to the gas engine; Receiving the constant signal and the load signal, when the pressure value indicated by the supply pressure setting signal is larger than the allowable upper limit value of the engine supply pressure setting value for the engine load, the allowable upper limit value is set to the engine supply pressure setting value. If the allowable lower limit is smaller than the allowable lower limit, the allowable lower limit is used as an engine supply pressure set value in other cases, and the engine supply pressure set value is corrected based on the supply air temperature. And a pressure controller for outputting an operation signal for operating the bypass valve in a direction to cancel the difference based on a difference between the value and a detected supply pressure in the engine supply passage.

Further, a third invention is a power generating gas engine which is coaxial with a turbine driven by engine exhaust gas and which is combined with a turbocharger which sends out air mixed with gas fuel by a compressor which rotates integrally therewith. In the combustion control device, the exhaust gas supply flow path of the turbine is directly connected to the exhaust gas discharge flow path via a bypass valve, and the temperature of the exhaust gas in the exhaust gas supply flow path is detected to correspond to the detected temperature. A temperature controller that outputs an air supply pressure setting signal that indicates an engine air supply pressure that causes an air / fuel ratio to change, and an engine air supply corresponding to the detected concentration by detecting a NOx concentration in an exhaust gas discharge passage of the turbine. A Nox controller that outputs a signal indicating the pressure with the supply pressure corresponding to the allowable Nox concentration as a lower limit, the supply pressure signal and the Nox control And a load detector that detects the output of a generator driven by the gas engine and outputs a detection output as a load signal, While detecting the supply pressure in the engine supply passage from the compressor to the gas engine, receiving the signal and the load signal from the high selector, the pressure value indicated by the signal from the high selector indicates the engine supply pressure with respect to the engine load. If the set value is larger than the allowable upper limit,
When the engine supply pressure set value is smaller than the allowable lower limit value, the allowable lower limit value is set as the engine supply pressure setting value in other cases. A pressure controller for outputting an operation signal for operating the bypass valve in a direction to cancel the difference based on a difference between the detected supply pressure and the supply pressure in the air flow path is provided.

Further, a fourth invention is a power generating gas engine which is coaxial with a turbine driven by engine exhaust gas and which is combined with a turbocharger which sends out air mixed with gas fuel by a compressor which rotates integrally therewith. In the combustion control device, the bypass flow path directly connecting the exhaust gas supply flow path of the turbine to the exhaust gas discharge flow path via a bypass valve, and the NOx in the exhaust gas discharge flow path of the turbine
A Nox controller for detecting a concentration and outputting a concentration signal; detecting an exhaust gas temperature in the exhaust gas supply flow path; correcting the detected temperature based on the concentration signal; A temperature controller that outputs a supply pressure setting signal indicating an engine supply pressure that produces a fuel ratio; a load detector that detects an output of a generator driven by the gas engine and outputs a detection output as a load signal. While detecting the supply pressure in the engine supply passage from the compressor to the gas engine, receiving the supply pressure setting signal and the load signal, the pressure value indicated by the supply pressure setting signal indicates the engine supply pressure to the engine load. If the air pressure setting value is larger than the allowable upper limit value, the allowable upper limit value is set. If the air supply pressure setting value is smaller than the allowable lower limit value, the allowable lower limit value is set. The pressure value and the engine air supply pressure set value if, based on a difference between the detected boost pressure of the engine air charge pressure setpoint and the engine air supply flow path,
A pressure controller for outputting an operation signal for operating the bypass valve in a direction to cancel the difference is provided.

[0009]

According to the first aspect of the present invention, the supply pressure of the gas engine is always in a stable combustion region below the allowable upper limit of the supply pressure set value, and is higher than the allowable lower limit of the supply pressure set value. , The gas engine does not misfire, the exhaust gas temperature is kept in an appropriate range, and as a result, the NOx concentration in the exhaust gas is kept low. Further, with the configuration as in the second invention, even when the outside air temperature changes, the above-described operation described with respect to the first invention can be performed without being affected by the change.
Furthermore, by configuring as in the third invention and the fourth invention, the supply pressure of the gas engine is set so that the concentration of NOx in the exhaust gas from the gas engine is equal to or less than an allowable value, and the stable combustion region and the fuel consumption good region are set. As a result, the gas engine does not misfire and the exhaust gas temperature is kept in the proper range.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 to 3 show a gas engine power generation facility to which the combustion control device according to the first invention is applied. The gas engine power generation facility shown in FIG. 10 is provided with a pressure controller 15 instead of the pressure controller 14. Temperature controller 1 in the exhaust gas supply passage 6
6 are substantially the same except for the point that a signal is input to the pressure controller 15 and the contents of control are provided. Corresponding portions are denoted by the same reference numerals and description thereof is omitted. . Here, the temperature controller 15 detects the exhaust gas temperature and outputs a supply pressure setting signal indicating an engine supply pressure that generates an air / fuel ratio corresponding to the detected temperature.

Further, the pressure controller 15 will be described together with the control by the combustion control device. FIG. 2 shows the relationship between the engine load, that is, the output of the generator 5 and the upper and lower limits of the engine supply pressure that generates the air / fuel ratio corresponding to the load, by using a curve I (upper limit) and a curve II (lower limit). It is. In other words, the area below the curve I is a stable combustion area, the area above the curve II is a good fuel economy area, and the hatched portion between the curves I and II is an appropriate operation area of the gas engine 4.

As shown in FIG. 3, the pressure controller 15 includes function generators 21 and 22, a high limiter 23, and a low limiter 2.
The function generator 21 outputs a supply pressure signal corresponding to a load signal based on a function representing the curve I and the function generator 22. Then, first, the pressure controller 15 receiving the supply pressure setting signal outputs the smaller one of the supply pressure setting signal and the signal from the function generator 21 by the high limiter 23, and outputs the signal from the high limiter 23 by the low limiter 24. The larger of the signal and the signal from the function generator 22 is output. The signal from the low limiter 24 is input to an air supply pressure controller 25, which cancels the difference with respect to the bypass valve 8 based on the difference from the detected value of the air supply pressure in the engine air supply passage 12. An operation signal to operate in the direction is output. In this way, the supply air pressure is always kept in the proper operation range, the temperature of the exhaust gas from the gas engine 4 is properly maintained without causing a misfire of the gas engine 4, and as a result, the NOx concentration in the exhaust gas is reduced to a low value. To keep it.

FIGS. 4 to 6 show a gas engine power generation system to which the combustion control apparatus according to the second invention is applied, and FIGS.
Is provided with a pressure controller 15a in place of the pressure controller 15, and the pressure controller 15a
Are substantially the same except that the air supply temperature in addition to the air supply pressure in the engine air supply flow path 12 is detected. Omitted. As shown in FIG. 5, the pressure controller 15a includes function generators 21 and 22, a high limiter 23, and a low limiter 2.
4. In addition to the air supply pressure controller 25, a temperature compensator 26 to which the above temperature signal is input is built in.
Assuming that the value of the output signal from X is X, the value of the temperature signal is A, and the reference value is B, the value Y of the signal input to the air supply pressure controller 25 is Y = X · (A / B). It is formed so as to make correction based on the temperature signal.

Accordingly, the function of the pressure controller 15a is, as a result, as shown in FIG.
B) The signal from the low limiter 24 is directly supplied to the air supply unit by shifting the signal from the low limiter 24 so as to be a doubled value, that is, when the air supply temperature is high, the line is indicated by a dashed line, and when the air supply temperature is low, the line is indicated by a broken line. This is the same as when inputting to the pressure controller 25. FIG. 7 shows a gas engine power generation equipment to which the combustion control device according to the third invention is applied, and is different from the gas engine power generation equipment shown in FIG. 1 in that a Nox controller 27 and a high selector 28 are newly provided. The other parts are substantially the same, and the corresponding parts are denoted by the same reference numerals and description thereof will be omitted.

Here, the NOx controller 27 detects the NOx concentration in the exhaust gas discharge passage 7 of the turbine 1 and outputs a signal indicating the engine supply pressure corresponding to the detected concentration to an allowable NOx concentration.
The engine supply pressure corresponding to the concentration is output as the lower limit. The high selector 28 is connected to the temperature controller 16.
And the signal from the NOx controller 27 is output to the pressure controller 15 as a supply pressure setting signal. With the above-described configuration, the air supply pressure is set to a value that allows the Nox concentration in the exhaust gas to be equal to or lower than the allowable upper limit.
The engine is designed to correspond to the fuel ratio and is kept in the above-mentioned proper operation range so that the exhaust gas temperature does not rise abnormally without causing the gas engine to misfire.

FIG. 8 shows a gas engine power generation equipment to which the combustion control device according to the fourth invention is applied. The gas engine power generation equipment shown in FIG.
8 is substantially the same except that a temperature controller 16a for receiving a signal from the Nox controller 27 is provided instead of 8, and corresponding parts are denoted by the same reference numerals and description thereof is omitted. . Here, the temperature controller 16a is a Nox controller 27
The detected temperature is corrected so as to be lower as the signal from the controller becomes larger, and the supply pressure corresponding to the corrected temperature is input to the pressure controller 15 as a supply pressure setting signal. Therefore, the larger the signal from the Nox controller 27, the larger the supply pressure setting signal.

According to the above configuration, as in the case of the third aspect, the supply pressure corresponds to the air / fuel ratio that makes the NOx concentration in the exhaust gas equal to or less than the allowable upper limit value, and is maintained in the appropriate operation range. The exhaust gas temperature is prevented from abnormally rising without causing a misfire of the gas engine. The first to fourth inventions are not limited to the above embodiment. In addition, for example, the high limiter 23 may be a low selector that outputs the smaller one of the two input signals, and may be a low limiter 24.
May be replaced by a high selector that outputs the larger of the two input signals, and the arrangement order of these is not limited to the above embodiment.

The pressure controller 15 in the third and fourth inventions is the same as the pressure controller 15a in the second invention.
A temperature compensator may be built in, and the gas temperature in the engine air supply passage 12 may be detected. FIG.
Shows a gas engine power generation facility to which a combustion control device for directly adjusting the NOx concentration in the exhaust gas is applied similarly to the third and fourth inventions, and the parts common to the gas engine power generation facilities shown in FIGS. The same numbers are assigned and the description is omitted. In this gas engine power generation facility, the exhaust gas discharge passage 7
A Nox controller 27a for detecting the concentration of NOx in the exhaust gas and outputting a concentration signal is provided, and this concentration signal is input to a limiter 29.

On the other hand, the gas engine 4 is provided with an ignition timing adjusting device 30 for adjusting the ignition timing of the gas engine 4 based on a signal from the limiter 29. That is, when the concentration signal input to the limiter 29 is equal to or higher than the allowable upper limit value, the ignition timing is delayed. 30 is formed. By forming in this manner, the concentration of Nox in the exhaust gas is kept within an allowable range. Note that this combustion control device may be used in combination with the combustion control devices according to the first and second inventions, whereby the exhaust gas temperature control and the NOx concentration control can be performed more reliably.

[0020]

As is apparent from the above description, according to the first invention, the bypass passage, the temperature controller, the load detector, and the pressure controller are provided and formed. For this reason,
The effect of keeping the supply pressure of the gas engine in the proper operation range, good fuel economy, preventing the gas engine from misfiring, preventing the exhaust gas temperature from abnormally rising, and keeping the NOx concentration in the exhaust gas low as a result. Play. Also, the second
According to the invention, the same bypass channel, temperature controller,
In addition to the load detector, the temperature of the supply air in the supply passage of the gas engine is also detected, and a pressure controller having a built-in temperature corrector is provided. For this reason, it is possible to prevent abnormal rise in exhaust gas temperature without being affected by fluctuations in the supply air temperature, always achieving good fuel efficiency and causing misfiring of the gas engine, and to keep the NOx concentration in exhaust gas low. It works.

Further, according to the third aspect of the present invention, a Nox controller and a high selector are provided in addition to the bypass channel, the temperature controller, the load detector, and the pressure controller, which are the same as those described above. According to the fourth invention, in addition to the bypass channel, the load detector, the pressure controller, and the Nox controller similar to those described above,
It is provided with a temperature controller which receives a signal from the x controller and corrects the detected temperature. For this reason, Nox in exhaust gas
This has the effect of keeping the concentration within an allowable range, good fuel economy, and preventing an abnormal rise in exhaust gas temperature without causing a gas engine misfire.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a gas engine power generation facility to which a combustion control device according to a first invention is applied.

FIG. 2 is a diagram showing a relationship between an engine load and an engine supply pressure.

FIG. 3 is a block diagram showing a configuration of a pressure controller in FIG.

FIG. 4 is an overall configuration diagram of a gas engine power generation facility to which a combustion control device according to a second invention is applied.

FIG. 5 is a block diagram showing a configuration of a pressure controller in FIG.

FIG. 6 is a diagram showing a relationship between an engine load and an engine supply pressure when the supply air temperature changes.

FIG. 7 is an overall configuration diagram of a gas engine power generation facility to which a combustion control device according to a third invention is applied.

FIG. 8 is an overall configuration diagram of a gas engine power generation facility to which a combustion control device according to a fourth invention is applied.

FIG. 9 is an overall configuration diagram of a gas engine power generation facility to which a combustion control device in which the ignition timing is changed to adjust the NOx concentration in exhaust gas is applied.

FIG. 10 is an overall configuration diagram of a gas engine power generation facility to which a conventional combustion control device is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbine 2 Compressor 3 Turbocharger 4 Gas engine 5 Generator 6 Exhaust gas supply flow path 7 Exhaust gas discharge flow path 8 Bypass valve 9 Bypass flow path 12 Engine air supply flow path 13 Load detector 15, 15a Pressure controller 16, 16a Temperature control Total 26 Temperature compensator 27 Nox controller 28 High selector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-291435 (JP, A) JP-A-60-8424 (JP, A) JP-A-63-285223 (JP, A) JP-A-2- 115538 (JP, A) JP-A-61-277857 (JP, A) JP-A-56-145702 (JP, A) JP-A 1-149534 (JP, U) JP-A 63-46630 (JP, U) Actually open sho 61-162554 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02B 33/00-39/16 F02D 19/02 F02D 29/06

Claims (4)

(57) [Claims] 1. A combustion control device for a gas engine for power generation, which is coaxial with a turbine driven by engine exhaust gas and combined with a turbocharger for sending air mixed with gas fuel by a compressor that rotates integrally therewith. A bypass passage directly connecting the exhaust gas supply passage of the turbine to the exhaust gas discharge passage via a bypass valve, and detecting an exhaust gas temperature in the exhaust gas supply passage to determine an air / fuel ratio corresponding to the detected temperature. A temperature controller that outputs a supply pressure setting signal indicating an engine supply pressure to be generated, a load detector that detects an output of a generator driven by the gas engine and outputs a detection output as a load signal, While detecting the supply pressure in the engine supply passage from the compressor to the gas engine, receiving the supply pressure setting signal and the load signal, If the pressure value indicated by the air pressure setting signal is larger than the allowable upper limit value of the engine supply pressure set value for the engine load, the allowable upper limit value is set. The allowable lower limit value, in other cases, the pressure value is set as an engine supply pressure set value, and based on a difference between the engine supply pressure set value and the detected supply pressure in the engine supply passage,
A combustion controller for a gas engine for power generation, comprising: a pressure controller for outputting an operation signal for operating the bypass valve in a direction to cancel the difference. 2. A combustion control apparatus for a gas engine for power generation, which is coaxial with a turbine driven by engine exhaust gas and combined with a turbocharger for sending air mixed with gas fuel by a compressor that rotates integrally therewith. A bypass passage directly connecting the exhaust gas supply passage of the turbine to the exhaust gas discharge passage via a bypass valve, and detecting an exhaust gas temperature in the exhaust gas supply passage to determine an air / fuel ratio corresponding to the detected temperature. A temperature controller that outputs a supply pressure setting signal indicating an engine supply pressure to be generated, a load detector that detects an output of a generator driven by the gas engine and outputs a detection output as a load signal, While detecting the supply pressure and supply temperature in the engine supply passage from the compressor to the gas engine, the supply pressure setting signal, load signal When the pressure value indicated by the supply pressure setting signal is larger than the allowable upper limit of the engine supply pressure set value for the engine load,
When the engine supply pressure setting value is smaller than the allowable lower limit value, the allowable lower limit value is used as the engine supply air pressure setting value in other cases, and the engine supply air pressure setting value is used as the engine supply air pressure setting value. A pressure controller that outputs an operation signal for operating the bypass valve in a direction to cancel the difference based on a difference between a correction value obtained by temperature correction based on a temperature and a detected supply pressure in the engine supply passage. And a combustion control device for a gas engine for power generation. 3. A combustion control apparatus for a gas engine for power generation, which is coaxial with a turbine driven by engine exhaust gas and combined with a turbocharger that sends air mixed with gas fuel by a compressor that rotates integrally therewith. A bypass passage directly connecting the exhaust gas supply passage of the turbine to the exhaust gas discharge passage via a bypass valve, and detecting an exhaust gas temperature in the exhaust gas supply passage to determine an air / fuel ratio corresponding to the detected temperature. A temperature controller that outputs a supply pressure setting signal indicating an engine supply pressure to be generated, and a Nox concentration in the exhaust gas discharge passage of the turbine, and a signal indicating an engine supply pressure corresponding to the detected concentration. , Allowable N
No that outputs the supply pressure corresponding to the ox concentration as the lower limit
An x controller, a high selector for receiving a signal from the supply pressure signal and the signal from the Nox controller, and outputting a signal indicating a high pressure among them, and detecting an output of a generator driven by the gas engine. A load detector that outputs a detection output as a load signal, and detects a supply pressure in an engine supply passage from the compressor to the gas engine while receiving a signal and a load signal from the high selector, and If the pressure value indicated by the signal from is larger than the allowable upper limit value of the engine supply pressure set value for the engine load, the allowable upper limit value is set. In other cases, the lower limit is used as the engine supply pressure set value, and the pressure value is used as the engine supply pressure set value. And a pressure controller for outputting an operation signal for operating the bypass valve in a direction to cancel the difference based on the difference with the supply air pressure. . 4. A combustion control apparatus for a gas engine for power generation, which is coaxial with a turbine driven by engine exhaust gas and combined with a turbocharger for sending air mixed with gas fuel by a compressor rotating integrally therewith. A bypass flow path that directly connects the exhaust gas supply flow path of the turbine to the exhaust gas discharge flow path via a bypass valve, a Nox controller that detects a Nox concentration in the exhaust gas discharge flow path of the turbine and outputs a concentration signal, The exhaust gas temperature in the exhaust gas supply passage is detected, the detected temperature is corrected based on the concentration signal, and an air supply pressure setting indicating an engine air supply pressure that generates an air / fuel ratio corresponding to the corrected temperature. A temperature controller that outputs a signal, and a load detector that detects the output of a generator driven by the gas engine and outputs the detected output as a load signal And an air supply pressure in the engine air supply passage from the compressor to the gas engine, while receiving the air supply pressure setting signal and the load signal, and the pressure value indicated by the air supply pressure setting signal corresponds to the engine load. This allowable upper limit value is set when the allowable value of the engine supply pressure set value is larger than the allowable upper limit value, the allowable lower limit value is set when the set value of the engine air supply pressure is smaller than the allowable lower limit value, and the pressure limit is set otherwise. A value is set as an engine supply pressure set value, and based on a difference between the engine supply pressure set value and the detected supply pressure in the engine supply passage, the bypass valve operates in a direction to cancel the difference. A combustion controller for a gas engine for power generation, comprising: a pressure controller that outputs an operation signal to cause the pressure to be generated.