JP6508709B2 - Air-fuel ratio control device for gas engine and ship equipped with gas engine with air-fuel ratio control device - Google Patents

Description

  The present invention relates to an air-fuel ratio control device for a gas engine that mixes and burns fuel gas and air to obtain power, and a ship equipped with a gas engine with an air-fuel ratio control device.

  A gas engine that mixes fuel gas and air and burns to obtain power is environmentally friendly, high in thermal efficiency, and economical, so it is often used as a prime mover for cogeneration plants, and environmental regulations are becoming stricter. Gas engines are beginning to be installed on even the emerging ships. However, gas engines, especially lean burn gas engines, are vulnerable to load fluctuations, and particularly when used as ship engines, a number of control devices are provided to perform air-fuel ratio control in order to cope with load fluctuations due to rough seas. There is.

FIG. 6 is a schematic block diagram of a conventional air-fuel ratio control device, FIG. 7 is a diagram showing air-fuel ratio control with respect to engine load fluctuation of the conventional air-fuel ratio control device, and FIG. 8 is a diagram showing necessity of air-fuel ratio control.
In FIG. 8, the vertical axis is the net mean effective pressure (BMEP), and the horizontal axis is the excess air ratio (the ratio of the actual amount of air to the theoretically required air). In lean combustion, if the excess air ratio is smaller than the desired excess air ratio, knocking tends to occur, and if the excess air ratio exceeds, the misfire tends 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 an appropriate air-fuel ratio for preventing knocking and misfiring.
The conventional air-fuel ratio control device includes a gas engine 100 and a turbocharger 200 having a turbine 210 and a compressor 220, as shown in FIG. The air fuel ratio control unit 300 includes a throttle valve 310, a variable valve timing mechanism 320, a variable geometry turbo 330, a fuel supply unit 340, and the like. The exhaust gas bypass path 350 and the exhaust gas bypass control valve (Waste gate valve) 360 are controlled.
In order to adjust and control the amount of air, the throttle valve 310 is provided at the outlet of the compressor 220 of the turbocharger 200 to control the air supply amount, and at the same time, the variable nozzle 330 provided on the turbine 210 side of the turbocharger 200. Control and control to release excess exhaust gas with the exhaust gas bypass control valve 360 are necessary. Furthermore, it is necessary to adjust the exhaust energy by means of a variable valve timing mechanism 320 provided on the gas engine 100 side for changing the timing of intake and exhaust. By such control, air-fuel ratio control can be performed, and dynamic characteristics that endure marine use can be obtained.
However, in the conventional air-fuel ratio control method, in the case of changing the supply amount of the fuel gas and the air in order to maintain the output of the engine in response to the load fluctuation etc. Since the response is fast, the mixing balance of the fuel gas and the air is broken, and as shown in FIG. 7, the air-fuel ratio fluctuates and the combustion becomes unstable.

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 value of the air supply pressure and the air supply temperature in the air supply passage. A method of controlling an air-fuel ratio of a gas engine is disclosed, in which the air supply amount in the air supply passage is controlled by the air supply and release means so that the actual air amount matches the required air amount.
In addition, Patent Document 2 calculates the optimum fuel gas amount and the air supply pressure, by calculating the calorific value of the fuel gas supplied to the engine and the optimum heat amount corresponding to the optimum heat quantity at the time of operation including the start of the engine. The electric motor connected to the supercharger to calculate the optimum number of revolutions of the supercharger that matches the actual air volume calculated based on the value and the air supply temperature detection value, and to achieve the optimum supercharger rotation number A motor driven supercharger gas engine is disclosed which comprises a motor controller controlling the motor.
Further, in Patent Document 3, a fuel gas flow rate command value is calculated based on a deviation between an engine rotational speed signal detected from a gas engine and a speed command value signal serving as a target value thereof, and the fuel gas flow rate command value is calculated. Speed control step of setting the fuel gas flow rate of the fuel flow rate control valve, and calculating a mixed air flow amount command value to be an appropriate air fuel ratio with respect to the fuel gas flow rate command value; An air-fuel ratio control step of performing feedback control to set a target opening degree of a throttle valve based on the deviation of the above is disclosed.
Further, in Patent Document 4, a target fuel corresponding to each of the air supply pressure and the engine load is a fuel injection amount based on the detected value of the air supply pressure from the air supply pressure sensor and the detected value of the engine load from the load detector. The fuel injection amount is adjusted to either the turbocharger rotational speed or the exhaust pressure based on the detected value of the turbocharger rotational speed or the exhaust pressure input from the turbocharger rotational speed detector or the exhaust pressure sensor while adjusting to the injection amount. A fuel control device for a diesel engine for power generation is disclosed that includes a control device that adjusts the target fuel injection amount corresponding to one or both of them.

Unexamined-Japanese-Patent No. 2003-261239 JP 2007-218223 A JP, 2009-57870, A Unexamined-Japanese-Patent No. 2006-307676

In order to stably burn a gas engine, especially a lean combustion gas engine without knocking or misfiring, the air fuel ratio should be set even if the setting of the amount of fuel gas supplied is changed, such as when the load fluctuates. It is necessary to control it regularly. However, it is difficult to improve the controllability such as responsiveness even if many devices for controlling the air-fuel ratio are added, and the number of devices increases and the reliability tends to be reduced due to the complexity.
In the air-fuel ratio control method of the gas engine of Patent Document 1, it is necessary to detect the fuel flow rate, the air supply pressure and the air supply temperature to calculate the required air amount and the actual air amount. It requires an air supply and discharge means for discharging a part to the outside.
Moreover, the gas engine with a motor drive supercharger of patent document 2 calculates the optimal fuel gas amount, detects the air supply pressure and the air supply temperature, calculates the optimal number of revolutions of the supercharger, and controls the electric motor. It is difficult to keep the air-fuel ratio constant at the time of load fluctuation since the control is not performed in consideration of the responsiveness of the device for controlling the air-fuel ratio.
Moreover, the control method of the gas engine of Patent Document 3 requires feedback control to perform each calculation based on the detected engine rotational speed and set a target opening degree of the throttle valve. Since control is not performed in consideration of responsiveness, it is difficult to keep the air-fuel ratio constant at load fluctuation.
Moreover, although the fuel control apparatus of the diesel engine for electric power generation of patent document 4 uses several detection values, such as an air supply pressure, an engine load, supercharger rotation speed, and an exhaust pressure, for control, fuel-air control is carried out. It is difficult to keep the air-fuel ratio constant at the time of load fluctuation because it is intended to maintain appropriate responsiveness in the system and to perform control in consideration of the responsiveness of the turbocharger. Moreover, it is a control device related to a diesel engine for power generation, and does not relate to a gas engine that requires finer control than the diesel engine.

Therefore, the present invention keeps the air-fuel ratio constant even if the setting of the fuel supply amount of the fuel gas is changed, for example, when the load fluctuates without adding a large number of devices for controlling the air-fuel ratio. It is an object of the present invention to provide an air-fuel ratio control device of a gas engine excellent in responsiveness and a ship equipped with the gas engine with the air-fuel ratio control device.

An air-fuel ratio control apparatus for a gas engine according to claim 1 is an air-fuel ratio control apparatus for a gas engine which mixes fuel gas and air and burns to obtain power, which is a fuel gas supplied to the gas engine. A supercharger having a fuel supply amount control means for controlling a fuel supply amount, a compressor for pressurizing air and a turbine driven by exhaust gas of a gas engine, and a turbocharger rotation for detecting the number of revolutions of the turbocharger The rate of increase or decrease in the amount of supplied air until the required amount of air is reached based on the detection results of the number of detection means and the change in the fuel supply amount of the fuel gas based on the detection result of the turbocharger rotational speed detection means. seeking, seeking an increase rate or decrease rate of the fuel supply quantity to maintain the proper air-fuel ratio, based on the increase rate or decrease rate of the fuel supply quantity, fuel by fast fuel supply amount controller responsive the supercharger Characterized by comprising a air-fuel ratio control means for controlling so as to slow down the change over time in fuel supply flow rate of the gas.
When the load fluctuates, the response of the supercharger is delayed, but the response of the fuel supply control means is faster than that of the supercharger. Therefore, the setting of the fuel supply of the fuel gas is changed when the load fluctuates. when it is, the air-fuel ratio for better fuel supply amount of the fuel gas than air bellflower supply amount reaches the required amount earlier combustion fluctuates becomes unstable. Therefore, according to the present invention as set forth in claim 1, the fuel supply amount control means delays the temporal change of the fuel supply amount of the fuel gas based on the number of revolutions of the turbocharger, that is, the fuel supply of the fuel gas by slower timed until the amount reaches a required amount of air bellflower feed amount, and the air-fuel ratio without increasing much the device for controlling the air-fuel ratio constant, stabilizing the combustion in the gas engine Can.

  The present invention according to claim 2 is characterized in that the fuel supply amount control means is a solenoid valve which is turned on / off digitally. According to the second aspect of the present invention, by using a general on / off type solenoid valve as the fuel supply amount control means, the fuel supply amount control means is not complicated and can be made inexpensive and reliable. Sex can also be configured highly.

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 present invention described in claim 3, by controlling the duty ratio of the solenoid valve, control of the fuel supply amount of the fuel gas by the fuel supply amount control means can freely be slow temporal change it can.

According to a fourth aspect of the present invention, the engine rotational speed detecting means for detecting the engine rotational speed of the gas engine is provided, and the air fuel ratio control means performs control based on the detection result of the engine rotational speed detection means. Do. According to the present invention described in claim 4, it is possible to calculate the gas flow rate in consideration of the rotational speed of the engine, the air-fuel ratio control means, the fuel supply amount of the fuel gas based on a more accurate gas flow rate Control over time.

According to a fifth aspect of the present invention, the air-fuel ratio control means is provided with an energizing means for energizing the supercharger, and the air-fuel ratio control means detects the detection result of the supercharger rotational speed detecting means when the setting of the fuel supply amount of the fuel gas is changed. And controlling the biasing means on the basis of. According to the fifth aspect of the present invention, for example, in the case where the number of revolutions of the turbocharger is lower than the required number of revolutions, that is, when the air supply amount is insufficient, the supercharging is performed by the booster. The number of revolutions of the machine can be increased to ensure the required amount of air quickly.

  The invention according to claim 6 is characterized in that the energizing means is a motor / generator having a function of driving the supercharger and rotating by the supercharger to generate power. According to the present invention as set forth in claim 6, when the number of revolutions of the turbocharger is lower than the required number of revolutions, that is, when the amount of supplied air is insufficient, the use of the turbocharger as a motor for energizing is excessive. Increase the number of revolutions of the feeder to secure the required amount of air, and if the number of revolutions of the turbocharger is higher than the required number of revolutions, that is, if the amount of air supply is excessive, rotate the turbocharger by generating power as a generator. Can reduce the amount of air supply.

According to a seventh aspect of the present invention, the throttle valve is provided in the path between the compressor of the turbocharger and the gas engine, and the air fuel ratio control means changes the setting of the fuel supply amount of the fuel gas. The throttle valve is controlled based on the detection result of the rotational speed detection means. According to the seventh aspect of the present invention, for example, when the number of revolutions of the turbocharger is lower than the required number of revolutions, that is, when the amount of supplied air is insufficient, the amount of supplied air can be increased by opening the fast response throttle valve. It can be increased quickly.

  The present invention according to claim 8 is characterized in that the air-fuel ratio control means controls the throttle valve to be in a throttled position during steady load. According to the present invention as set forth in claim 8, by throttling the throttle valve at the time of steady load, it is possible to provide extra capacity at the time of load rise.

According to a ninth aspect of the present invention, the variable nozzle is provided on the upstream side of the turbine of the supercharger, and the air-fuel ratio control means detects the supercharger rotational speed when the setting of the fuel supply amount of the fuel gas is changed. The variable nozzle is controlled based on the detection result of According to the present invention, for example, when the number of revolutions of the supercharger is lower than the required number of revolutions, that is, when the amount of supplied air is insufficient, the direction or angle of the nozzle blade of the variable nozzle having quick response By changing the exhaust gas passage to adjust the flow velocity of the exhaust gas supplied from the gas engine, the pressurization characteristic of pressurized air can be improved, the amount of supplied air can be increased quickly, and the air-fuel ratio can be easily maintained constant. .

The present invention according to claim 10 includes a bypass path bypassing a turbine of a turbocharger and a bypass control valve opening and closing the bypass path, and the air-fuel ratio control means changes the setting of the fuel supply amount of fuel gas. In this case, the bypass control valve is controlled based on the detection result of the turbocharger rotational speed detection means. According to the present invention as set forth in claim 10, when the number of revolutions of the turbocharger is lower than the required number of revolutions, that is, when the air supply amount is insufficient, the opening degree of the bypass path opened in advance is bypassed with quick response. The control valve can increase the number of revolutions of the throttling turbocharger to rapidly increase the air supply amount. Also, if the rotational speed of the turbocharger is higher than the required rotational speed, the bypass control valve is opened to flow the exhaust gas in the bypass path to bypass the turbine to reduce the rotational speed of the turbocharger to reduce the air supply amount. 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 rotational speed of the turbocharger when the setting of the fuel supply amount of the fuel gas is changed. The variable pitch propeller is controlled based on the result. According to the eleventh aspect of the present invention, the air-fuel ratio can be easily kept constant by changing the pitch of the quick response variable pitch propeller to increase or decrease the load applied to the gas engine.

A ship equipped with a gas engine equipped with an air-fuel ratio control device according to claim 12 is characterized in that the air-fuel ratio control device for a gas engine according to any one of claims 1 to 11 is provided. Do. According to the present invention as set forth in claim 12, the fuel supply amount control means delays the temporal change of the fuel supply amount of the fuel gas based on the rotational speed of the supercharger, that is, the fuel supply amount of the fuel gas by slower timed to reach the required amount of air bellflower supply amount can be an air-fuel ratio without increasing much the device for controlling the air-fuel ratio constant, to stabilize the combustion in the gas engine It is possible to provide a ship equipped with a gas engine with an air-fuel ratio control device.

According to the present invention, the fuel supply amount control means delays the temporal change of the fuel supply amount of the fuel gas based on the rotational speed of the turbocharger, that is, until the fuel supply amount of the fuel gas reaches the required amount. the time that slow to suit the sky bellflower feed amount, and the air-fuel ratio without increasing much the device for controlling the air-fuel ratio constant, it is possible to stabilize the combustion in a gas engine.

  In addition, when the fuel supply amount control means is a solenoid valve that turns on / off digitally, the fuel supply amount control means is controlled by using a general on / off type solenoid valve as the fuel supply amount control means. It can be configured inexpensively and highly reliably without making the means complicated.

Further, the air-fuel ratio control means, when controlling the duty ratio of the solenoid valve, by controlling the duty ratio of the solenoid valve, control of the fuel supply amount of the fuel gas by the fuel supply amount control means can be freely, Temporal change can be delayed.

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

The air-fuel ratio control means controls the energizing means based on the detection result of the turbocharger rotational speed detecting means when the setting of the fuel supply amount of the fuel gas is changed. In the case where the number of revolutions of the supercharger is lower than the required number of revolutions, that is, when the air supply amount is insufficient, for example, the number of revolutions of the supercharger is increased by energizing the supercharger by the adder. The required amount of air can be secured quickly.

  Further, in the case where the energizing means is a motor / generator having a function of driving the supercharger and rotating by the supercharger to generate power, the case where the number of revolutions of the supercharger is lower than the required number of revolutions, that is, air When the amount of supply is insufficient, the turbocharger is used as a motor to boost the number of revolutions of the turbocharger to increase the required amount of air, and the number of revolutions of the turbocharger is higher than the number of revolutions required In the case where the air supply amount is excessive, the power generation as a generator can reduce the air supply amount by suppressing the rotation of the turbocharger.

Further, a throttle valve is provided in a path between the compressor of the turbocharger and the gas engine, and the air-fuel ratio control means detects the detection result of the turbocharger rotation speed detection means when the setting of the fuel supply amount of the fuel gas is changed. In the case of controlling the throttle valve on the basis of, for example, when the number of revolutions of the supercharger is lower than the required number of revolutions, that is, when the air supply amount is insufficient, the air supply amount can be It can be increased quickly.

  Further, when the air-fuel ratio control means performs control to make the throttle valve come to the throttled position during steady load, by throttling the throttle valve at steady load, it is possible to have extra power in preparation for load rise. Can.

Further, a variable nozzle is provided upstream of the turbine of the turbocharger, and the air-fuel ratio control unit is variable based on the detection result of the turbocharger rotation number detection unit when the setting of the fuel supply amount of the fuel gas is changed. When controlling the nozzles, for example, when the number of revolutions of the turbocharger is lower than the required number of revolutions, that is, when the air supply amount is insufficient, the exhaust gas passage is By changing the flow rate of the exhaust gas supplied from the gas engine by adjusting it, the pressurization characteristic of the pressurized air can be improved, the amount of supplied air can be rapidly increased, and the air-fuel ratio can be easily kept constant.

In addition, a bypass path bypassing the turbocharger turbine and a bypass control valve opening and closing the bypass path are provided, and the air-fuel ratio control means changes the setting of the fuel supply amount of the fuel gas. When controlling the bypass control valve based on the detection result of the detection means, if the number of revolutions of the supercharger is lower than the required number of revolutions, that is, if the air supply amount is insufficient, the bypass path opened in advance is opened. The quick response bypass control valve can increase the number of revolutions of the squeezer and increase the amount of air supply rapidly. Also, if the rotational speed of the turbocharger is higher than the required rotational speed, the bypass control valve is opened to flow the exhaust gas in the bypass path to bypass the turbine to reduce the rotational speed of the turbocharger to reduce the air supply amount. Can be reduced quickly.

The air-fuel ratio control means is provided with a variable pitch propeller driven by a gas engine, and the variable pitch propeller is controlled based on the detection result of the turbocharger rotational speed detection means when the setting of the fuel supply amount of the fuel gas is changed. In order to control the air-fuel ratio, it is easy to 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.

Furthermore, when the air-fuel ratio control apparatus for a gas engine according to any one of claims 1 to 11 is provided in a ship, the time of the fuel supply amount of fuel gas based on the number of revolutions of the supercharger changes the slowing in the fuel supply amount control means, i.e. the time until the fuel supply amount of the fuel gas reaches the required amount by slow to suit the sky bellflower supply amount, a device for controlling the air-fuel ratio It is possible to provide a ship equipped with a gas engine equipped with an air-fuel ratio control device capable of stabilizing combustion in the gas engine by making the air-fuel ratio constant without increasing much.

The schematic block diagram of the ship carrying the gas engine with an air fuel ratio control device by one embodiment of the present invention Schematic configuration diagram of air-fuel ratio control system of the same gas engine Diagram showing air-fuel ratio control for engine load fluctuation of the same air-fuel ratio controller The schematic block diagram of the air fuel ratio control apparatus of the gas engine by other embodiment of this invention Diagram showing air-fuel ratio control for engine load fluctuation of the same air-fuel ratio controller Schematic configuration diagram of a conventional air-fuel ratio control device Diagram showing air-fuel ratio control for engine load fluctuation of the same air-fuel ratio controller Diagram showing the necessity of air-fuel ratio control

Hereinafter, an air-fuel ratio control device for a gas engine according to an embodiment of the present invention, and a ship equipped with a gas engine with an air-fuel ratio control device will be described.
FIG. 1 is a schematic diagram of a ship equipped with a gas engine with an air-fuel ratio controller according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an air-fuel ratio controller of the gas engine, and FIG. 3 is an air-fuel ratio controller It is a figure which shows the air fuel ratio control with respect to the engine load fluctuation of.

As shown in FIG. 1, the ship equipped with the gas engine with air-fuel ratio control device of the present embodiment is provided with a drive source 4 for driving a propeller 3 on the stern 2 side of the hull 1.
The drive source 4 has a lean burn gas engine 10 that mixes and burns fuel gas and air to obtain power, and a turbocharger 20. The supercharger 20 is driven by the exhaust gas exhausted from the gas engine 10 to supply the gas engine 10 with pressurized air.
The gas engine 10 may be a super lean combustion type other than the lean combustion type, or may be a gas engine of another type having the same problem when the load changes.

Next, an air-fuel ratio control device of the same gas engine will be described with reference to FIG.
The air-fuel ratio control device for a gas engine according to the present embodiment includes a fuel supply amount control unit 30 that controls the supply amount of fuel gas supplied to the gas engine 10, and a turbocharger rotation speed that detects the rotational speed of the turbocharger 20. A detection means 31 and an air-fuel ratio control means 32 for controlling an air-fuel ratio which is a mixture ratio of air and fuel gas are provided.
The supercharger 20 includes a turbine 21 provided in an exhaust path of the gas engine 10 and driven by the exhaust gas, a compressor 22 operated by the turbine 21 to pressurize air, and an upstream side (exhaust gas introduction side) of the turbine 21 And a variable nozzle 23 disposed.
The variable nozzle 23 can change the exhaust gas passage depending on the direction and angle of the nozzle blade, adjust the flow velocity of the exhaust gas supplied from the gas engine 10, and improve the pressurization characteristic of the pressurized air.
An air cooler (not shown) is provided in the path from the supercharger 20 to the gas engine 10, and the air pressurized and heated by the compressor 22 is cooled by the air cooler and the gas engine is cooled. It will be introduced in ten.
The fuel supply amount control means 30 uses a solenoid valve which is turned on / off digitally. By using a general on / off type solenoid valve, the fuel supply amount control means 30 can be configured inexpensively and with high reliability without complication.

The air-fuel ratio control means 32 detects the number of revolutions of the supercharger when the amount of supplied fuel gas fluctuates due to a change in the instruction of the governor, a load fluctuation, disturbance or the like, that is, when the amount of supplied fuel gas is changed. By controlling the duty ratio of the solenoid valve 30 based on the detection result of the means 31, the control of the amount of fuel gas supplied by the solenoid valve 30 can be freely performed, 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 rotational speed of the gas engine 10. In the control, first, the actual air supply amount is calculated from the detected number of revolutions of the turbocharger 20, and the increase speed or decrease speed of the air supply amount until reaching the required air amount is determined. Next, based on the increase speed or decrease speed of the air supply amount until reaching the required air amount and the predetermined proper air-fuel ratio, the required amount of fuel gas supplied does not deviate from the proper air-fuel ratio The increase rate or decrease rate of the supplied amount of fuel gas is set so as to reach. Then, 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.

If the load fluctuates, the response of the supercharger 20 is delayed, but the response of the solenoid valve 30 is faster than the supercharger 20. Therefore, when the setting of the fuel gas supply amount is changed, the air is supplied. Since the amount of fuel gas supplied reaches the necessary amount earlier than the amount, the air-fuel ratio fluctuates and combustion becomes unstable. Therefore, as in the present embodiment, the rotational speed of the turbocharger 20 is detected, and based on the detection result, the temporal change in the amount of fuel gas supplied by the solenoid valve 30 is delayed (the amount of fuel gas supplied is required). By making the increase rate or decrease rate until the amount is reached), the air-fuel ratio can be prevented from fluctuating and made constant according to the temporal change of the air supply amount (see FIG. 3). ). Therefore, the combustion in the gas engine 10 can be stabilized.
As shown in FIG. 3, when the load of the gas engine 10 rises, 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 rotational speed constant to prevent a power failure due to a reduction in rotational speed, etc., the load is the propeller 3 of the ship as in this embodiment. In addition, since it is possible to maintain a constant propulsive force even if the rotational speed of the gas engine 10 decreases, control to maintain the air-fuel ratio constant can be prioritized over maintaining the rotational speed to be constant.

Further, the air-fuel ratio control device for a gas engine of the present embodiment includes an engine rotational speed detection unit 33 that detects the engine rotational 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 in setting the increase rate or decrease rate of the fuel gas supply rate until the fuel gas supply rate reaches the required amount, the time of the fuel gas supply rate can be more accurately Change can be controlled.
Furthermore, by utilizing the fact that the engine speed detecting means 33 can detect the speed of the gas engine 10, and maintaining the air-fuel ratio when the load rises, the case where the speed of the gas engine 10 exceeds the lower limit (the gas engine 10 In the case where the engine is stopped) or when the rotational speed of the gas engine 10 becomes dangerous beyond the upper limit when the load decreases, the air-fuel ratio control by the air-fuel ratio control device is controlled to be discontinued. Can.

In addition, a throttle valve 26 is provided in a path between the compressor 22 of the turbocharger 20 and the gas engine 10.
The throttle valve 26 is controlled by the air-fuel ratio control means 32 to reach a throttled position during steady load. When the setting of the supply amount of the fuel gas is changed, the air-fuel ratio control means 32 detects that the rotational speed of the supercharger 20 is detected 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. At steady load, throttle valve 26 is squeezed to give remaining capacity, and when load increases, time to reach required air amount by opening fast response throttle valve 26 and rapidly increasing air supply amount Can be shortened, and the air-fuel ratio can be easily kept constant.

  Further, when the setting of the supply amount of the fuel gas is changed, 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. Do. For example, when the rotation speed of the supercharger 20 is lower than the required rotation speed, that is, when the air supply amount is insufficient, the exhaust gas passage is changed according to the direction and the angle of the nozzle blade of the variable nozzle 23 having quick response. Thus, it is possible to improve the pressurization characteristic of the pressurized air by adjusting the flow velocity of the exhaust gas supplied from the above, to rapidly increase the air supply amount, and to easily keep the air-fuel ratio constant.

Further, a bypass passage 24 branched from the exhaust gas passage between the gas engine 10 and the turbine 21 and bypassing the turbine 21 of the turbocharger 20 and joining the exhaust gas passage on the downstream side of the turbine 21; And a bypass control valve 25 that opens and closes the bypass path 24.
When the setting of the supply amount of the fuel gas is changed, 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. Take control. That is, when the number of revolutions of the supercharger 20 is lower than the necessary number of revolutions, 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 having quick response. The number of rotations of the machine 20 can be increased to rapidly increase the air supply amount. Further, when the rotation speed of the turbocharger 20 is higher than the necessary rotation speed, the bypass control valve 25 is opened to flow the exhaust gas to the bypass path 24 to bypass the turbine 21 to reduce the rotation speed of the turbocharger 20 Thus, the air supply can be reduced rapidly.
As described above, by causing the exhaust gas to bypass the turbine 21 according to the rotational speed of the turbocharger 20, the rotational speed of the turbocharger 20 can be adjusted, and the air-fuel ratio can be easily maintained constant.

Further, 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 its pitch is changed by oil pressure, a motor or the like.
When the setting of the supply amount of the fuel gas 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 rotational speed of the supercharger 20 by the supercharger rotational speed detection means 31. Take control. That is, when the rotation speed of the supercharger 20 is smaller or larger than the necessary rotation speed, the air-fuel ratio is made constant by changing the pitch of the quick response variable pitch propeller 3 to increase or decrease the load applied to the gas engine 10 It becomes 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, but the fuel gas and air are mixed in advance, and the air is mixed. The supply amount may be controlled, and may be applied to, for example, a premixed lean-burn combustion gas engine. Further, the fuel supply amount control means 30 includes all means related to fuel supply such as a pilot fuel valve of a type for supplying a pilot fuel, and a plurality of fuel supply valves of a type for supplying an additional fuel. Further, the detection result of the supercharger rotational speed detection means 31 can be used for monitoring of operation during steady operation and management of the supercharger 20, in addition to control during load fluctuation. Further, the turbocharger rotational speed may be detected indirectly by using the turbocharger characteristic, the pressurizing pressure and the like.

An air-fuel ratio control apparatus for a gas engine according to another embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic block diagram of an air-fuel ratio control system for a gas engine according to another embodiment of the present invention, and FIG. 5 is a view showing air-fuel ratio control for engine load fluctuation of the air-fuel ratio control system. The same functional members as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof will be 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, and The present embodiment is different from the above-described embodiment in the provision point.

The motor / generator 40 is connected to the turbocharger 20.
When the setting of the supply amount of the fuel gas is changed, 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. I do. That is, when the number of revolutions of the turbocharger 20 is smaller than the necessary number of revolutions, that is, when the air supply amount is insufficient, the number of revolutions of the turbocharger 20 needs to be increased by using the turbocharger 20 as a motor. If the amount of air is secured quickly and the number of revolutions of the turbocharger 20 is greater than the required number of revolutions, that is, if the amount of air supply is excessive, the rotation of the turbocharger 20 is suppressed by generating electricity as a generator to reduce the amount of air supplied. Reduce Since the motor activation or generator generation is electrical, its operation is instantaneous. Therefore, when control of the motor / generator 40 is performed based on the detection result of the rotational speed of the turbocharger 20, as shown in FIG. At the same time, the drop in engine speed can be kept relatively short.
Further, in the present embodiment, the air-fuel ratio control means 32 temporally supplies the amount of fuel gas supplied by the solenoid valve 30 in addition to the control of the motor / generator 40 based on the detection result of the supercharger rotational speed detection means 31. Since the control for delaying the change is also performed, as shown in FIG. 5B, the air-fuel ratio can be made constant.
The biasing means 40 may be a motor not having a generator function, or may be a compressor such as an air compressor which boosts the turbocharger 20 using air pressure or oil pressure.

As described above in each embodiment, the air-fuel ratio control device of the gas engine according to the present invention detects the number of revolutions of the turbocharger 20, and based on the detection result, the fuel gas control unit 30 By delaying the temporal change of the supply amount, it is possible to make the air-fuel ratio constant according to the temporal change of the air supply amount. Therefore, the combustion in the gas engine 10 can be stabilized.
Further, it is possible to provide a ship equipped with the gas engine 10 with the air-fuel ratio control device.

  The air-fuel ratio control device for a gas engine according to the present invention can keep the air-fuel ratio constant by delaying temporal change in the amount of supplied fuel gas by the fuel supply amount control means based on the number of revolutions of the turbocharger. As it can, it can be applied to various gas engines for land and marine industries including ships.

Reference Signs List 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. Turbocharger rotational speed detection means 32. Air fuel ratio control means 33. Engine rotational speed detection means 40. Actuating means (motor / generator).

Claims (12)

A air-fuel ratio control system for a gas engine which obtains power by burning a mixture of fuel gas and air, and the fuel supply amount control means for controlling the fuel supply amount of the fuel gas supplied to the gas engine, the air And a turbocharger having a compressor driven by the exhaust gas of the gas engine, a turbocharger rotational speed detecting means for detecting the rotational speed of the turbocharger, and the fuel supply of the fuel gas When the setting of the amount is changed, the increase speed or the decrease speed of the air supply amount to reach the required air amount is obtained based on the detection result of the turbocharger rotational speed detection means, and the appropriate air fuel ratio is maintained. the calculated increase rate or decrease rate of the fuel supply amount, on the basis of the increase rate or decrease rate of the fuel supply amount, before said fuel gas by fast the fuel supply amount control means responsive than the supercharger Air-fuel ratio control device for a gas engine comprising the air-fuel ratio control means for controlling so as to slow down the change over time in fuel supply flow rate.   The air fuel ratio control device for a gas engine according to claim 1, wherein the fuel supply amount control means is a solenoid valve which is turned on / off digitally.   The air-fuel ratio control apparatus 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 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. Item 4. An air-fuel ratio control device for a gas engine according to any one of items 3 to 4. The air fuel ratio control means is provided with an energizing means for energizing the supercharger, and the air / fuel ratio control means is based on the detection result of the supercharger rotational speed detecting means when the setting of the fuel 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, characterized in that the control means controls the boosting means.   6. The air-fuel ratio control device for a gas engine according to claim 5, wherein the urging means is a motor / generator having a function of driving the supercharger and rotating by the supercharger to generate power. . A throttle valve is provided in a path between the compressor and the gas engine of the turbocharger.
The air-fuel ratio control means controls the throttle valve based on the detection result of the supercharger rotational speed detection means when the setting of the fuel supply amount of the fuel gas is changed. An air-fuel ratio control device for a gas engine according to any one of claims 1 to 4.   8. An air fuel ratio control system for a gas engine according to claim 7, wherein said air fuel ratio control means controls said throttle valve to be in a throttled position during steady load. A variable nozzle is provided on the upstream side of the turbine of the turbocharger, and the air-fuel ratio control unit detects the detection of the turbocharger rotation number detection unit when the setting of the fuel 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, wherein the variable nozzle is controlled based on a result. The turbocharger includes a bypass path bypassing the turbine of the turbocharger and a bypass control valve opening and closing the bypass path, and the air-fuel ratio control means changes the setting of the fuel supply amount of the fuel gas. The air-fuel ratio control device 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 turbocharger rotational speed detection means. The variable pitch propeller driven by the gas engine is provided, and the air-fuel ratio control means is based on the detection result of the supercharger rotational speed detection means when the setting of the fuel supply amount of the fuel gas is changed. 5. An air-fuel ratio control system for a gas engine according to claim 1, wherein said 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 of a gas engine according to any one of claims 1 to 11.