JP2016176338A - Air-fuel ratio control device of gas engine, and ship equipped with gas engine including air-fuel ratio control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device of a gas engine and a ship equipped with the gas engine including the air-fuel ratio control device, superior in responsiveness by keeping a constant air-fuel ratio even when the setting of a supply amount of a fuel gas is changed in the case where a load fluctuates, without additionally installing much apparatuses for controlling the air-fuel ratio.SOLUTION: An air-fuel ratio control device of a gas engine includes fuel supply amount control means 30 for controlling a supply amount of a fuel gas to be supplied to a gas engine 10, a supercharger 20 having a compressor 22 for pressurizing air and a turbine 21 driven by an exhaust gas of the gas engine 10, supercharger rotational frequency detection means 31 detecting a rotational frequency of the supercharger 20, and air-fuel ratio control means 32 for performing control so that temporal variation of the supply amount of the fuel gas by the fuel supply amount control means 30 is delayed on the basis of a result of the detection by the supercharger rotational frequency detection means 31 when the setting of the supply amount of the fuel gas is changed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an air-fuel ratio control device for a gas engine that obtains power by mixing and burning fuel gas and air, and a ship equipped with a gas engine with an air-fuel ratio control device.

  Gas engines that obtain power by mixing and burning fuel gas and air are environmentally friendly, have high thermal efficiency, and are economical, so they are often used as prime movers for cogeneration plants, and environmental regulations are becoming stricter. Gas engines are beginning to be installed in ships that are coming. However, gas engines, particularly lean combustion gas engines, are vulnerable to load fluctuations, and especially when used as marine engines, a large number of control devices are provided to perform air-fuel ratio control in order to cope with load fluctuations caused by rough seas. Yes.

6 is a schematic configuration diagram of a conventional air-fuel ratio control device, FIG. 7 is a diagram showing air-fuel ratio control with respect to engine load fluctuations of the conventional air-fuel ratio control device, and FIG. 8 is a diagram showing the necessity of air-fuel ratio control.
In FIG. 8, the vertical axis represents the net average effective pressure (BMEP), and the horizontal axis represents the excess air ratio (the ratio of the actual air amount to the theoretically required air). In lean combustion, if the excess air ratio is smaller than the desired excess air ratio, knocking is likely to occur, and if it is greater, misfire is likely to occur (the engine is likely to stop). It can be seen that the higher the net average effective pressure, the narrower the range of suitable air-fuel ratio for preventing knocking or misfire.
As shown in FIG. 6, the conventional air-fuel ratio control apparatus includes a gas engine 100 and a supercharger 200 having a turbine 210 and a compressor 220. The air-fuel ratio control unit 300 includes a throttle valve 310, a variable valve timing mechanism 320, a variable nozzle turbo 330, a fuel supply unit 340, The exhaust gas bypass path 350 and the exhaust gas bypass control valve 360 are controlled.
In order to adjust and control the amount of air, a throttle valve 310 is provided at the outlet of the compressor 220 of the supercharger 200 to control the air supply amount, and at the same time, the variable nozzle 330 provided on the turbine 210 side of the supercharger 200 is controlled. It is necessary to perform control and control to release excess exhaust gas using the exhaust gas bypass control valve 360. Further, it is necessary to adjust the exhaust energy by a variable valve timing mechanism 320 provided on the gas engine 100 side, which makes the intake and exhaust timing variable. By such control, air-fuel ratio control can be performed and dynamic characteristics that can withstand marine use can be obtained.
However, in the conventional air-fuel ratio control method, when the supply amounts of fuel gas and air are changed in order to maintain the output of the engine in response to load fluctuations or the like, the fuel supply means 340 is more than the supercharger 200. Since the response is fast, the mixing balance of the fuel gas and air is lost, and the air-fuel ratio fluctuates as shown in FIG.

Here, in Patent Document 1, the required air amount is calculated based on the detected value of the fuel flow rate in the fuel supply passage, and the actual air amount is calculated based on the detected values of the supply pressure and supply temperature in the supply passage. A gas engine air-fuel ratio control method is disclosed in which the air supply amount in the air supply passage is controlled by the air supply discharge means so that the actual air amount matches the required air amount.
Further, Patent Document 2 calculates the optimum fuel gas amount corresponding to the calorific value of the fuel gas supplied to the engine and the optimum heat amount during operation including when the engine is started, and detects the optimum fuel gas amount and supply air pressure. Electric motor connected to the turbocharger so as to obtain the optimum turbocharger rotation speed by calculating the optimum turbocharger rotation speed that matches the actual air amount calculated based on the value and the detected air temperature A gas engine with a motor-driven supercharger having a motor controller for controlling the motor is disclosed.
Further, in Patent Document 3, a fuel gas flow rate command value is calculated based on a deviation between an engine rotation speed signal detected from a gas engine and a speed command value signal as a target value, and the fuel gas flow rate command value is A speed control step for setting the fuel gas flow rate of the fuel flow rate control valve, and a mixture flow rate command value that provides an appropriate air-fuel ratio with respect to the fuel gas flow rate command value, and a mixture flow rate command value and an actual mixture flow rate An integrated control method for a gas engine is disclosed, which includes an air-fuel ratio control step for performing feedback control for setting a target opening of a throttle valve based on the deviation of the throttle valve.
Further, Patent Document 4 discloses a target fuel that corresponds to the fuel injection amount and the engine load based on the detected value of the supplied air pressure from the supplied air pressure sensor and the detected value of the engine load from the load detector, respectively. The fuel injection amount is adjusted to either the turbocharger speed or the exhaust pressure based on the detected value of the turbocharger speed or the exhaust pressure input from the turbocharger speed detector or the exhaust pressure sensor. There is disclosed a fuel control device for a diesel engine for power generation that includes a control device that adjusts the target fuel injection amount corresponding to one or both of them.

JP 2003-261239 A JP 2007-218223 A JP 2009-57870 A JP 2006-307676 A

In order for gas engines, especially lean combustion gas engines, to burn stably without causing knocking or misfire, the air-fuel ratio must be reduced even when the fuel gas supply amount is changed, such as when the load fluctuates. It needs to be controlled constantly. However, even if a large number of devices for controlling the air-fuel ratio are added, it is difficult to improve the controllability such as responsiveness, and the number of devices increases and the complexity tends to decrease.
In the air-fuel ratio control method of the gas engine disclosed in Patent Document 1, it is necessary to calculate the necessary air amount and the actual air amount by detecting the fuel flow rate, the supply air pressure, and the supply air temperature, as well as the supply air amount in the supply passage. A supply air discharge means for discharging a part of the air to the outside is required.
In addition, the gas engine with a motor-driven supercharger disclosed in Patent Document 2 calculates the optimum fuel gas amount, detects the supply air pressure and the supply air temperature, calculates the optimum rotation speed of the supercharger, and controls the electric motor. However, it is difficult to keep the air-fuel ratio constant when the load fluctuates because the control is not performed in consideration of the responsiveness of the device for controlling the air-fuel ratio.
In addition, the gas engine control method disclosed in Patent Document 3 requires feedback control to perform each calculation based on the detected engine rotational speed and set the target opening of the throttle valve. Since control is not performed in consideration of responsiveness, it is difficult to keep the air-fuel ratio constant when the load fluctuates.
Further, the fuel control device for a power generation diesel engine disclosed in Patent Document 4 uses a plurality of detected values such as a supply air pressure, an engine load, a supercharger rotation speed, and an exhaust pressure for control. The system maintains moderate response in the system and does not perform control in consideration of the response of the turbocharger, so it is difficult to keep the air-fuel ratio constant during load fluctuations. Moreover, it is a control apparatus regarding the diesel engine for electric power generation, and is not related to the gas engine which requires finer control than a diesel engine.

  Therefore, the present invention does not add many devices for controlling the air-fuel ratio, and keeps the air-fuel ratio constant even when the setting of the fuel gas supply amount is changed, such as when the load fluctuates. An object of the present invention is to provide a gas engine air-fuel ratio control device with excellent responsiveness and a ship equipped with the gas engine with the air-fuel ratio control device.

The air-fuel ratio control apparatus for a gas engine according to claim 1 is an air-fuel ratio control apparatus for a gas engine that obtains power by mixing fuel gas and air and combusting the fuel gas. Fuel supply amount control means for controlling the supply amount, a compressor for pressurizing air, a supercharger having a turbine driven by exhaust gas of a gas engine, and a supercharger rotational speed for detecting the rotational speed of the supercharger When the setting of the detection means and the fuel gas supply amount is changed, the temporal change of the fuel gas supply amount by the fuel supply amount control means is delayed based on the detection result of the supercharger rotation speed detection means. And an air-fuel ratio control means for controlling.
When the load fluctuates, the response of the turbocharger is delayed, but the fuel supply amount control means responds faster than the supercharger, so the setting of the fuel gas supply amount is changed, such as when the load fluctuates. In this case, since the fuel gas supply amount reaches the required amount earlier than the air supply amount, the air-fuel ratio fluctuates and combustion becomes unstable. Therefore, according to the first aspect of the present invention, the temporal change in the supply amount of the fuel gas is delayed by the fuel supply amount control means based on the rotational speed of the supercharger, that is, the supply amount of the fuel gas is reduced. By delaying the time required to reach the required amount according to the air supply amount, the air-fuel ratio can be kept constant without increasing the number of devices that control the air-fuel ratio, and combustion in the gas engine can be stabilized.

  According to a second aspect of the present invention, the fuel supply amount control means is a solenoid valve that is digitally turned on / off. According to the second aspect of the present invention, by using a general on / off type solenoid valve for the fuel supply amount control means, the fuel supply amount control means is inexpensive and reliable without complicating the fuel supply amount control means. It can also be configured with high performance.

  The present invention according to claim 3 is characterized in that the air-fuel ratio control means controls the duty ratio of the solenoid valve. According to the third aspect of the present invention, by controlling the duty ratio of the solenoid valve, it is possible to freely control the supply amount of the fuel gas by the fuel supply amount control means, and to delay the temporal change. .

  According to a fourth aspect of the present invention, the engine speed detecting means for detecting the engine speed of the gas engine is provided, and the air-fuel ratio control means performs control based on the detection result of the engine speed detecting means. To do. According to the fourth aspect of the present invention, since the gas flow rate can be calculated in consideration of the engine speed, the air-fuel ratio control means can control the supply amount of the fuel gas based on the more accurate gas flow rate. Time changes can be controlled.

  According to a fifth aspect of the present invention, there is provided an energizing means for energizing the supercharger, and the air-fuel ratio control means uses the detection result of the supercharger rotation speed detecting means when the fuel gas supply amount setting is changed. Based on this, the urging means is controlled. According to the fifth aspect of the present invention, for example, when the rotational speed of the supercharger is lower than the required rotational speed, that is, when the air supply amount is insufficient, supercharging is performed by energizing the supercharger by the urging means. The required air volume can be secured quickly by increasing the speed of the machine.

  The present invention described in claim 6 is characterized in that the urging means is a motor / generator having a function of driving the supercharger and rotating the turbocharger to generate electric power. According to the sixth aspect of the present invention, when the rotational speed of the supercharger is lower than the required rotational speed, that is, when the air supply amount is insufficient, the supercharger is used as a motor for energizing. Increase the rotation speed of the turbocharger to secure the required air volume. If the turbocharger rotation speed is higher than the required rotation speed, that is, if the air supply is excessive, rotate the turbocharger by generating electricity as a generator. It is possible to suppress the air supply and reduce the air supply amount.

  According to a seventh aspect of the present invention, a throttle valve is provided in a path between the compressor of the supercharger and the gas engine, and the air-fuel ratio control means rotates the supercharger when the setting of the fuel gas supply amount is changed. The throttle valve is controlled based on the detection result of the number detecting means. According to the seventh aspect of the present invention, for example, when the rotational speed of the supercharger is lower than the required rotational speed, that is, when the air supply amount is insufficient, the air supply amount is reduced by opening the throttle valve with quick response. It can increase quickly.

  The present invention according to claim 8 is characterized in that the air-fuel ratio control means performs control so that the throttle valve is brought to a throttled position during a steady load. According to the eighth aspect of the present invention, the throttle valve is throttled at the time of steady load, so that a surplus power can be provided in preparation for an increase in load.

  According to a ninth aspect of the present invention, a variable nozzle is provided on the upstream side of the turbocharger turbine, and the air-fuel ratio control means is configured to detect the supercharger rotation speed detection means when the fuel gas supply amount setting is changed. The variable nozzle is controlled based on the detection result. According to the ninth aspect of the present invention, for example, when the rotational speed of the supercharger is lower than the necessary rotational speed, that is, when the air supply amount is insufficient, the direction and angle of the nozzle blades of the variable nozzle with quick response The exhaust gas passage is changed to adjust the flow rate of the exhaust gas supplied from the gas engine to improve the pressurization characteristic of the pressurized air, the air supply amount can be increased quickly, and the air-fuel ratio can be kept constant. .

  The present invention according to claim 10 includes a bypass path that bypasses the turbine of the turbocharger and a bypass control valve that opens and closes the bypass path, and the air-fuel ratio control means is configured to change the fuel gas supply amount. Further, the bypass control valve is controlled based on the detection result of the supercharger rotation speed detection means. According to the tenth aspect of the present invention, when the rotation speed of the supercharger is lower than the required rotation speed, that is, when the air supply amount is insufficient, the opening degree of the bypass path opened in advance is bypassed quickly. The control valve can increase the rotation speed of the throttle supercharger and increase the air supply amount quickly. If the turbocharger speed is greater than the required speed, the bypass control valve is opened and exhaust gas flows through the bypass path to bypass the turbine, thereby reducing the turbocharger speed and supplying air Can be reduced quickly.

  The present invention according to claim 11 includes a variable pitch propeller driven by a gas engine, and the air-fuel ratio control means detects the detection result of the supercharger rotation speed detection means when the setting of the fuel gas supply amount is changed. The variable pitch propeller is controlled based on the above. According to the eleventh aspect of the present invention, it is possible to easily keep the air-fuel ratio constant by changing the pitch of the variable-pitch propeller with quick response to increase or decrease the load applied to the gas engine.

  A ship equipped with a gas engine with an air-fuel ratio control device corresponding to claim 12 is provided with the air-fuel ratio control device for a gas engine according to one of claims 1 to 11. To do. According to the twelfth aspect of the present invention, the temporal change of the fuel gas supply amount is delayed by the fuel supply amount control means based on the rotational speed of the supercharger, that is, the fuel gas supply amount is the required amount. The air-fuel ratio control that stabilizes the combustion in the gas engine by keeping the air-fuel ratio constant without delaying the time until it reaches the air flow according to the amount of air supply, without increasing the number of devices that control the air-fuel ratio A ship equipped with a gas engine with a device can be provided.

  According to the present invention, the time change of the fuel gas supply amount is delayed by the fuel supply amount control means based on the rotational speed of the supercharger, that is, the time until the fuel gas supply amount reaches the required amount. By delaying the air flow in accordance with the air supply amount, the air-fuel ratio can be kept constant without increasing the number of devices for controlling the air-fuel ratio, and combustion in the gas engine can be stabilized.

  Further, when the fuel supply amount control means is a solenoid valve that is digitally turned on / off, the fuel supply amount control means can be controlled by using a general on / off type solenoid valve for the fuel supply amount control means. The configuration can be made inexpensively and highly reliable without complicating the means.

  In addition, when the air-fuel ratio control means controls the duty ratio of the solenoid valve, the fuel gas supply amount can be freely controlled by the fuel supply amount control means by controlling the duty ratio of the solenoid valve. Changes can be slowed.

  The engine speed detection means for detecting the engine speed of the gas engine is provided, and the air-fuel ratio control means takes into account the engine speed when performing control based on the detection result of the engine speed detection means. Since the gas flow rate can be calculated, the air-fuel ratio control means can control the temporal change in the supply amount of the fuel gas based on the more accurate gas flow rate.

  The air-fuel ratio control means controls the urging means based on the detection result of the supercharger rotation speed detection means when the setting of the fuel gas supply amount is changed. In this case, for example, when the rotation speed of the supercharger is lower than the required rotation speed, that is, when the air supply amount is insufficient, it is necessary to increase the rotation speed of the supercharger by energizing the supercharger by the urging means. The amount of air can be secured quickly.

  Further, in the case where the urging means is a motor / generator having a function of driving the supercharger and rotating the supercharger to generate electric power, when the rotational speed of the supercharger is lower than the required rotational speed, that is, air If the supply amount is insufficient, use the turbocharger as a motor to boost the turbocharger to increase the rotation speed of the turbocharger to ensure the required air volume, and the turbocharger rotation speed is higher than the required rotation speed In this case, that is, when the air supply amount is excessive, it is possible to suppress the rotation of the supercharger and reduce the air supply amount by generating power as a generator.

  In addition, a throttle valve is provided in the path between the compressor of the supercharger and the gas engine, and the air-fuel ratio control means detects the detection result of the supercharger rotation speed detection means when the fuel gas supply amount setting is changed. In the case of controlling the throttle valve based on this, for example, when the rotational speed of the supercharger is lower than the required rotational speed, that is, when the air supply amount is insufficient, the air supply amount can be increased by opening the throttle valve with quick response. Can be increased.

  In addition, the air-fuel ratio control means, when controlling the throttle valve to be in the throttled position at the time of steady load, allows the throttle valve to be throttled at the time of steady load so as to have a surplus power in preparation for when the load increases. Can do.

  In addition, a variable nozzle is provided on the upstream side of the turbocharger turbine, and the air-fuel ratio control means is configured to change the variable nozzle based on the detection result of the supercharger rotation speed detection means when the fuel gas supply amount setting is changed. For example, when the rotational speed of the turbocharger is lower than the required rotational speed, that is, when the air supply amount is insufficient, the exhaust gas passage changes depending on the direction and angle of the nozzle blades of the variable nozzle that responds quickly. Thus, the flow rate of the exhaust gas supplied from the gas engine is adjusted to improve the pressurization characteristic of the pressurized air, the air supply amount can be increased quickly, and the air-fuel ratio can be easily kept constant.

  In addition, a bypass path that bypasses the turbocharger turbine and a bypass control valve that opens and closes the bypass path are provided, and the air-fuel ratio control means detects the turbocharger speed when the setting of the fuel gas supply amount is changed. When the bypass control valve is controlled on the basis of the detection result of the means, when the rotation speed of the supercharger is lower than the required rotation speed, that is, when the air supply amount is insufficient, the opening degree of the bypass path opened in advance By using a quick response bypass control valve, it is possible to increase the rotation speed of the throttle supercharger and increase the air supply amount quickly. If the turbocharger speed is greater than the required speed, the bypass control valve is opened and exhaust gas flows through the bypass path to bypass the turbine, thereby reducing the turbocharger speed and supplying air Can be reduced quickly.

  In addition, a variable pitch propeller driven by a gas engine is provided, and the air-fuel ratio control means controls the variable pitch propeller based on the detection result of the supercharger rotation speed detection means when the setting of the fuel gas supply amount is changed. In the case of control, the air-fuel ratio can be easily kept constant by changing the pitch of the variable pitch propeller that responds quickly to increase or decrease the load applied to the gas engine.

  When the air-fuel ratio control device for a gas engine according to one of claims 1 to 11 is provided in a ship, the amount of fuel gas supplied over time is determined based on the rotational speed of the supercharger. Increase the number of devices that control the air-fuel ratio by delaying the change with the fuel supply amount control means, that is, by delaying the time until the fuel gas supply amount reaches the required amount according to the air supply amount. Therefore, it is possible to provide a ship equipped with a gas engine equipped with an air-fuel ratio control device that can stabilize combustion in the gas engine while keeping the air-fuel ratio constant.

1 is a schematic configuration diagram of a ship equipped with a gas engine with an air-fuel ratio control device according to an embodiment of the present invention. Schematic configuration diagram of the air-fuel ratio control device of the gas engine The figure which shows the air fuel ratio control with respect to the engine load fluctuation | variation of the same air fuel ratio control apparatus The schematic block diagram of the air fuel ratio control apparatus of the gas engine by other embodiment of this invention The figure which shows the air fuel ratio control with respect to the engine load fluctuation | variation of the same air fuel ratio control apparatus Schematic configuration diagram of a conventional air-fuel ratio control device The figure which shows the air fuel ratio control with respect to the engine load fluctuation | variation of the same air fuel ratio control apparatus Diagram showing the necessity of air-fuel ratio control

Hereinafter, a gas engine air-fuel ratio control apparatus according to an embodiment of the present invention and a ship equipped with a gas engine with an air-fuel ratio control apparatus will be described.
FIG. 1 is a schematic configuration diagram of a ship equipped with a gas engine with an air-fuel ratio control device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an air-fuel ratio control device of the gas engine, and FIG. It is a figure which shows the air fuel ratio control with respect to the engine load fluctuation | variation.

As shown in FIG. 1, a ship equipped with the gas engine with an air-fuel ratio control device of the present embodiment includes a drive source 4 that drives a propeller 3 on the stern 2 side of the hull 1.
The drive source 4 includes a lean combustion type gas engine 10 that obtains power by mixing and burning fuel gas and air, and a supercharger 20. The supercharger 20 is driven by exhaust gas exhausted from the gas engine 10 and supplies pressurized air to the gas engine 10.
The gas engine 10 may be a super lean combustion type other than the lean combustion type, or another type of gas engine having the same problem when the load changes.

Next, the air-fuel ratio control apparatus for the gas engine will be described with reference to FIG.
The air-fuel ratio control apparatus for a gas engine according to the present embodiment includes a fuel supply amount control means 30 that controls the supply amount of fuel gas supplied to the gas engine 10 and a supercharger rotational speed that detects the rotational speed of the supercharger 20. A detection unit 31 and an air-fuel ratio control unit 32 that controls an air-fuel ratio that is a mixture ratio of air and fuel gas are provided.
The supercharger 20 is provided in an exhaust path of the gas engine 10 and driven by exhaust gas, a compressor 22 that operates by the turbine 21 and pressurizes air, and an upstream side (exhaust gas introduction side) of the turbine 21. And a variable nozzle 23 to be arranged.
The variable nozzle 23 can improve the pressurization characteristic of the pressurized air by changing the exhaust gas passage according to the direction and angle of the nozzle blade and adjusting the flow rate of the exhaust gas supplied from the gas engine 10.
An air cooler (not shown) is provided in the path from the supercharger 20 to the gas engine 10, and the air that has been pressurized by the compressor 22 and heated to a high temperature is cooled by the air cooler and then the gas engine. 10 is introduced.
The fuel supply amount control means 30 uses a solenoid valve that is digitally turned on / off. By using a general on / off type solenoid valve, the fuel supply amount control means 30 can be configured at low cost and with high reliability without being complicated.

The air-fuel ratio control means 32 detects the supercharger rotation speed when the fuel gas supply amount fluctuates due to a change in the governor instruction, load fluctuation, or disturbance, that is, when the fuel gas supply amount setting is changed. By controlling the duty ratio of the solenoid valve 30 based on the detection result of the means 31, the supply amount of fuel gas by the solenoid valve 30 can be freely controlled, and the temporal change can be delayed.
That is, when the load on the gas engine 10 increases or decreases, the air supply amount and the gas fuel supply amount are controlled to increase or decrease in order to maintain the rotation speed of the gas engine 10. In the control, first, an actual air supply amount is calculated from the detected rotational speed of the supercharger 20, and an increase rate or a decrease rate of the air supply amount until the required air amount is reached is obtained. Next, based on the increase or decrease rate of the air supply amount until the required air amount is reached and the predetermined appropriate air-fuel ratio, the fuel gas supply amount is reduced to the required amount without deviating from the appropriate air-fuel ratio. An increase rate or a decrease rate of the supply amount of the fuel gas is set so as to reach. The air-fuel ratio control means 32 controls the solenoid valve 30 based on the set increase rate or decrease rate of the fuel gas supply amount.

When the load fluctuates, the response of the supercharger 20 is delayed. However, since the solenoid valve 30 responds faster than the supercharger 20, if the setting of the fuel gas supply amount is changed, the supply of air is performed. Since the supply amount of the fuel gas reaches the required amount earlier than the amount, the air-fuel ratio fluctuates and the combustion becomes unstable. Therefore, as in this embodiment, the rotational speed of the supercharger 20 is detected, and the temporal change in the fuel gas supply amount by the solenoid valve 30 is delayed based on the detection result (the fuel gas supply amount is required). By slowing the rate of increase or decrease until reaching the amount, the air-fuel ratio can be prevented from fluctuating and kept constant in accordance with the temporal change in the air supply amount (see FIG. 3). ). Therefore, combustion in the gas engine 10 can be stabilized.
As shown in FIG. 3, when the load of the gas engine 10 increases, the air-fuel ratio is constant, but the rotational speed of the gas engine 10 is greatly reduced. However, unlike the case where the load is a generator and it is necessary to keep the rotation speed constant in order to prevent a power failure due to a decrease in the rotation speed, the load is the propeller 3 of the ship as in this embodiment. Since a constant propulsive force can be maintained even when the rotational speed of the gas engine 10 decreases, control for maintaining the air-fuel ratio constant can be prioritized over maintaining the rotational speed constant.

The air-fuel ratio control apparatus for a gas engine according to the present embodiment includes an engine speed detection means 33 that detects the engine speed of the gas engine 10.
The air-fuel ratio control means 32 calculates the actual gas flow rate in consideration of the rotational speed of the gas engine 10 and increases the fuel gas supply amount until the fuel gas supply amount reaches the required amount. Used to calculate speed or decrease speed. By using the actual gas flow rate as a parameter when setting the increase or decrease rate of the fuel gas supply amount until the fuel gas supply amount reaches the required amount, the time of the fuel gas supply amount can be more accurately Change can be controlled.
Further, by utilizing the fact that the engine speed detection means 33 can detect the speed of the gas engine 10, when the speed of the gas engine 10 exceeds the lower limit in order to maintain the air-fuel ratio when the load increases, the gas engine 10 If the rotation speed of the gas engine 10 exceeds the upper limit and becomes dangerous when the load decreases, control is performed so that the air-fuel ratio control by the air-fuel ratio control device is stopped. Can do.

Further, a throttle valve 26 is provided in a path between the compressor 22 of the supercharger 20 and the gas engine 10.
The throttle valve 26 faces the throttle position during steady load under the control of the air-fuel ratio control means 32. When the setting of the fuel gas supply amount is changed, the air-fuel ratio control means 32 determines that the detection result of the rotational speed of the supercharger 20 by the supercharger rotational speed detection means 31 is smaller than the required rotational speed, that is, air. If it is determined that the supply amount is insufficient, the throttle valve 26 is opened to increase the air supply amount. When the load is increased, the throttle valve 26 is throttled to have a surplus power, and when the load increases, the throttle valve 26 having a quick response is opened and the air supply amount is increased rapidly to reach the required air amount. And the air-fuel ratio can be easily kept constant.

  The air-fuel ratio control means 32 controls the variable nozzle 23 based on the detection result of the rotational speed of the supercharger 20 by the supercharger rotational speed detection means 31 when the setting of the fuel gas supply amount is changed. To do. For example, when the rotational speed of the supercharger 20 is lower than the required rotational speed, that is, when the air supply amount is insufficient, the exhaust gas passage is changed depending on the direction and angle of the nozzle blades of the variable nozzle 23 that responds quickly, and the gas engine 10 By adjusting the flow rate of the exhaust gas supplied from the air, the pressurization characteristics of the pressurized air can be improved, the air supply amount can be increased quickly, and the air-fuel ratio can be easily kept constant.

Further, a bypass path 24 branched from the exhaust gas passage between the gas engine 10 and the turbine 21, bypasses the turbine 21 of the supercharger 20, and joins the exhaust gas passage on the downstream side of the turbine 21, and the bypass path 24 And a bypass control valve 25 that opens and closes the bypass path 24.
The air-fuel ratio control means 32 opens and closes the bypass control valve 25 based on the detection result of the rotational speed of the supercharger 20 by the supercharger rotational speed detection means 31 when the setting of the fuel gas supply amount is changed. Take control. That is, when the rotational speed of the supercharger 20 is lower than the required rotational speed, that is, when the air supply amount is insufficient, the opening degree of the bypass path 24 opened in advance is throttled by the bypass control valve 25 with quick response, and supercharging is performed. The number of rotations of the machine 20 can be increased and the air supply amount can be increased rapidly. Further, when the rotational speed of the supercharger 20 is larger than the required rotational speed, the bypass control valve 25 is opened, exhaust gas flows through the bypass path 24, and the turbine 21 is bypassed to reduce the rotational speed of the supercharger 20. The air supply amount can be reduced quickly.
As described above, the exhaust gas bypasses the turbine 21 in accordance with the rotational speed of the supercharger 20, whereby the rotational speed of the supercharger 20 can be adjusted, and the air-fuel ratio can be easily kept constant.

In the present embodiment, the propeller 3 is a variable pitch propeller. The variable pitch propeller 3 is driven by the gas engine 10 and the pitch is changed by hydraulic pressure, a motor or the like.
When the setting of the fuel gas supply amount is changed, the air-fuel ratio control means 32 determines the pitch of the variable pitch propeller 3 based on the detection result of the supercharger 20 rotation speed by the supercharger rotation speed detection means 31. Take control. That is, when the rotational speed of the supercharger 20 is smaller or larger than the required rotational speed, the air-fuel ratio is made constant by changing the pitch of the variable pitch propeller 3 that responds quickly to increase or decrease the load on the gas engine 10. Easy to keep.

  In the present embodiment, the fuel supply amount control means (solenoid valve) 30 has been described as controlling the supply amount of the fuel gas. However, the fuel gas and air are mixed in advance, and the fuel gas mixed with the air is supplied. The supply amount may be controlled, and can be applied to, for example, a premixed lean burn combustion type gas engine. Further, the fuel supply amount control means 30 includes all the means related to fuel supply such as a pilot fuel valve of a type for supplying pilot fuel and a plurality of fuel supply valves of a type for supplying additional fuel. Further, the detection result of the supercharger rotation speed detection means 31 can be used for monitoring the operation during steady operation and managing the supercharger 20 in addition to the control at the time of load fluctuation. Moreover, you may detect a supercharger rotation speed indirectly using a supercharger characteristic, pressurization pressure, etc. FIG.

A gas engine air-fuel ratio control apparatus according to another embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a schematic configuration diagram of an air-fuel ratio control device for a gas engine according to another embodiment of the present invention, and FIG. 5 is a diagram showing air-fuel ratio control for engine load fluctuations of the air-fuel ratio control device. Note that members having the same functions as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.
The air-fuel ratio control apparatus for a gas engine according to the present embodiment does not include the variable nozzle 23, the bypass path 24, the bypass control valve 25, the throttle valve 26, and the engine speed detection means 33, but includes a motor / generator 40 that is an urging means. It differs from the above-mentioned embodiment in the point provided.

The motor / generator 40 is connected to the supercharger 20.
The air-fuel ratio control means 32 controls the motor / generator 40 based on the detection result of the rotational speed of the supercharger 20 by the supercharger rotational speed detection means 31 when the setting of the fuel gas supply amount is changed. I do. That is, when the rotational speed of the supercharger 20 is smaller than the required rotational speed, that is, when the air supply amount is insufficient, the supercharger 20 is used as a motor for energizing the turbocharger 20 to increase the rotational speed. When the amount of air is secured fast and the rotational speed of the supercharger 20 is greater than the required rotational speed, that is, when the air supply amount is excessive, the generator 20 generates power and suppresses the rotation of the supercharger 20 to reduce the air supply amount. Reduce. Since the energization as a motor or the power generation as a generator is electrical, the operation is performed instantaneously. Therefore, when the motor / generator 40 is controlled based on the detection result of the rotational speed of the supercharger 20, it becomes easy to suppress the fluctuation of the air-fuel ratio below a certain level as shown in FIG. At the same time, the drop in engine speed can be kept in a relatively short time.
Further, in the present embodiment, the air-fuel ratio control means 32 determines the amount of fuel gas supplied by the solenoid valve 30 over time based on the detection result of the supercharger rotation speed detection means 31 in addition to the control of the motor / generator 40. Since the control for delaying the change is also performed, the air-fuel ratio can be made constant as shown in FIG.
The urging means 40 may be a motor that does not have a generator function, or may urge the supercharger 20 using air pressure or hydraulic pressure such as an air compressor.

As described above, the air-fuel ratio control device for a gas engine according to the present invention detects the number of rotations of the supercharger 20 and determines the amount of fuel gas by the fuel supply amount control means 30 based on the detection result. By delaying the temporal change in the supply amount, the air-fuel ratio can be made constant in accordance with the temporal change in the air supply amount. Therefore, combustion in the gas engine 10 can be stabilized.
Moreover, the ship carrying the gas engine 10 with the air-fuel ratio control apparatus can be provided.

  The air-fuel ratio control device for a gas engine of the present invention can keep the air-fuel ratio constant by slowing the temporal change in the fuel gas supply amount by the fuel supply amount control means based on the rotation speed of the supercharger. Therefore, it can be applied to various gas engines for land and marine industries including ships.

DESCRIPTION OF SYMBOLS 10 Gas engine 20 Supercharger 21 Turbine 22 Compressor 23 Variable nozzle 24 Bypass path 25 Bypass control valve 26 Throttle valve 30 Fuel supply amount control means (solenoid valve)
31 Supercharger speed detection means 32 Air-fuel ratio control means 33 Engine speed detection means 40 Energizing means (motor / generator)

Claims (12)

  An air-fuel ratio control device for a gas engine that obtains power by mixing fuel gas and air for combustion, a fuel supply amount control means for controlling the supply amount of the fuel gas supplied to the gas engine, and the air A turbocharger having a compressor for pressurization and a turbine driven by exhaust gas of the gas engine, a supercharger rotation speed detection means for detecting the rotation speed of the supercharger, and the supply amount of the fuel gas. An air-fuel ratio control means for controlling the fuel gas supply amount control means so as to delay the temporal change in the fuel gas supply amount based on the detection result of the supercharger rotation speed detection means when the setting is changed. An air-fuel ratio control device for a gas engine, comprising:   2. The air-fuel ratio control apparatus for a gas engine according to claim 1, wherein the fuel supply amount control means is a solenoid valve that is digitally turned on / off.   The air-fuel ratio control device for a gas engine according to claim 2, wherein the air-fuel ratio control means controls a duty ratio of the solenoid valve.   The engine speed detection means for detecting the engine speed of the gas engine is provided, and the air-fuel ratio control means performs control based on the detection result of the engine speed detection means. Item 4. The air-fuel ratio control device for a gas engine according to item 1 of item 3.   The air-fuel ratio control means includes an urging means for urging the supercharger, and the air-fuel ratio control means is configured to change the setting of the supply amount of the fuel gas based on the detection result of the supercharger rotation speed detection means. The air-fuel ratio control apparatus for a gas engine according to any one of claims 1 to 4, wherein the urging means is controlled.   6. The air / fuel ratio control apparatus for a gas engine according to claim 5, wherein the urging means is a motor / generator that has a function of driving the supercharger and rotating the supercharger to generate electric power. . A throttle valve is provided in a path between the compressor of the supercharger and the gas engine;
The air-fuel ratio control means controls the throttle valve based on the detection result of the supercharger rotation speed detection means when the setting of the supply amount of the fuel gas is changed. The air-fuel ratio control device for a gas engine according to any one of claims 1 to 4.   8. The air-fuel ratio control apparatus for a gas engine according to claim 7, wherein the air-fuel ratio control means controls the throttle valve to face a throttle position during a steady load.   A variable nozzle is provided on the upstream side of the turbine of the supercharger, and the air-fuel ratio control means detects the detection result of the supercharger rotation speed detection means when the setting of the supply amount of the fuel gas is changed. 5. The air-fuel ratio control apparatus for a gas engine according to claim 1, wherein the variable nozzle is controlled based on the control.   A bypass path that bypasses the turbine of the turbocharger; and a bypass control valve that opens and closes the bypass path, and the air-fuel ratio control means is configured to perform the overload when the setting of the supply amount of the fuel gas is changed. The air-fuel ratio control apparatus for a gas engine according to any one of claims 1 to 4, wherein the bypass control valve is controlled based on the detection result of the charger rotation speed detection means.   A variable pitch propeller driven by the gas engine, wherein the air-fuel ratio control means is based on the detection result of the supercharger rotation speed detection means when the supply amount of the fuel gas is changed. The air-fuel ratio control apparatus for a gas engine according to any one of claims 1 to 4, wherein the variable pitch propeller is controlled. A ship equipped with a gas engine with an air-fuel ratio control device, comprising the air-fuel ratio control device for a gas engine according to one of claims 1 to 11.