WO2019049362A1

WO2019049362A1 - Engine operation method and engine system

Info

Publication number: WO2019049362A1
Application number: PCT/JP2017/032662
Authority: WO
Inventors: 隆典黒岩; 橋本　徹
Original assignee: 新潟原動機株式会社
Priority date: 2017-09-11
Filing date: 2017-09-11
Publication date: 2019-03-14
Also published as: SG11202002151WA; JPWO2019049362A1; JP6843250B2; CN111094726A; CN111094726B

Abstract

A four-stroke dual-fuel engine (1) that is for propelling a ship and that operates by switching between a gas mode, in which a gas fuel speed-regulating control is carried out using a gas fuel as a primary heat source, an assist mode, in which a liquid fuel speed-regulating control is carried out using both the gas fuel and a liquid fuel as the fuel, and a diesel mode, in which a speed-regulating control is carried out using only the liquid fuel as the fuel. A control unit (22) of the engine (1) has an operation control unit (49) for carrying out operational control of the engine, a gas governor (44) for carrying out a speed-regulating control related to the amount of gas fuel supplied, and a diesel governor (48) for carrying out a speed-regulating control related to the amount of liquid fuel supplied. During operation in the assist mode, when the output of the engine 1 enters an assist-off region, which is a region on either side of and including a cube root characteristic line for the ship, the engine operation moves to the gas mode. During operation in the gas mode, when the output of the engine (1) enters an assist-on region in which the output is higher than in the assist-off region the engine operation moves to the assist mode.

Description

Engine operating method and engine system

The present invention relates to, for example, a method of operating a 4-stroke dual fuel engine for propulsion of a ship and an engine system.

In recent years, regulations on the emission of air pollutants from engines for ship propulsion have been tightened. Therefore, there is a demand for the introduction of a dual fuel engine that can use gaseous fuel such as gas as a fuel, can emit less air pollutants, and can meet emission control regulations. The dual fuel engine is an engine that can use both gaseous fuel and liquid fuel as fuel.

For example, in the engine device described in Patent Document 1, fuel control in transitioning the operating state between the gas mode and the diesel mode is described. When switching the operation mode from the gas mode to the diesel mode, the fuel oil is monotonously increased while performing the speed control for the fuel gas supply amount, and when the fuel oil supply amount becomes equal to or more than the switching threshold, the speed control is performed for the fuel oil supply amount. While doing this, the amount of fuel gas supplied is monotonically decreased. When switching the operation mode from the diesel mode to the gas mode, control is performed according to the reverse procedure. In addition, it is stated that instantaneous switching can be performed only when switching from the gas mode to the diesel mode.

The diesel engine described in Patent Document 2 discloses a longitudinally swept two-stroke large-sized diesel engine. As a method of operating this large-sized diesel engine, while operating in the gas mode, it is operated in the transient mode when detecting a state of strong change in load. In the transient mode, there is a step of determining an upper threshold of the amount of fuel gas and determining an additional amount of liquid fuel introduced into the combustion space in addition to the gas for each work cycle of the large diesel engine. doing.

The engine control device described in Patent Document 3 is a method for controlling an engine that can be driven using both liquid fuel and gas fuel. In this method, it is described that the size of the total output to be output from the engine is divided into a liquid fuel share and a gas fuel share according to a predetermined ratio.

A dual fuel engine that is capable of both gaseous fuel operation and liquid fuel operation is usually operated with gaseous fuel (gas mode), and in emergency or unsteady operation with liquid fuel (diesel mode) or It is known to operate with both gaseous and liquid fuels.

In addition, among diesel engines using liquid fuel, one having a variable intake valve timing (VIVT) mechanism is known.
For example, in the example of the drive mechanism of the variable valve timing mechanism shown in FIG. 17, the exhaust valve swing arm 103 and the intake valve swing arm 105 connected to the rocker arm 127 via the push rod 128 are tappets of the crank link shaft 104. It is connected to the shaft 106 (the fulcrum position of the swing arm). By changing (rotating) the phase of the crank-like link shaft 104 by the actuator, the fulcrum positions of the intake valve swing arm 105 and the exhaust valve swing arm 103 change, and as a result, the contact position to the camshaft 108 changes.
As a result, the timing at which the eccentric cam 108a of the camshaft 108 presses the exhaust valve swing arm 103 or the intake valve swing arm 105 by the camshaft 108 is made variable in timing.

JP, 2017-57774, A JP, 2016-217348, A Patent 4975702 gazette

By the way, in the four-stroke engine for ship propulsion, in order to cope with various driving situations, the speed control of the amount of fuel supplied by the governor (speed control apparatus) is performed. In this speed control, the amount of fuel to be supplied is not predetermined, and the amount of fuel supplied is controlled as needed so as to maintain a constant target rotational speed. In the dual fuel engine that performs speed control, for example, as described in Patent Document 1, switching from the gas mode to the diesel mode can be performed in a short time. However, it is difficult to switch from the diesel mode to the gas mode in a short time.

That is, in the gas mode, the operable air-fuel ratio range in which the appropriate fuel can be obtained is limited to a narrow range, and therefore the altitude is high to appropriately control the supply amount of the gaseous fuel while maintaining the appropriate air-fuel ratio. Technology was necessary and difficult. Moreover, the switch from the diesel mode to the rapid gas mode causes knocking and misfires. In the case of a dual fuel engine as described in Patent Document 1, there is a problem that it takes several tens of seconds to switch from the diesel mode to the gas mode in actual operation.
In the prior art, since it takes time to switch from the operation mode by liquid fuel control to the operation mode by gas fuel control, the transition to the liquid fuel operation mode is an emergency It is positioned as a means, and it was difficult to return to the operation mode by the gas fuel regulation control under conditions where the output fluctuation is severe.

The present invention has been made in view of the above-mentioned problems, and in the case of performing speed control of the fuel supply amount by the governor, the mutual transition between the operation by the gaseous fuel and the operation using the liquid fuel is further enhanced. An object of the present invention is to provide a dual fuel engine operation method and an engine system that can be performed quickly and smoothly.

The present invention relates to a method of operating a dual fuel engine, and during the first operation in which the gas fuel is the major part of the heat source, the control of the supply amount of the gas fuel is terminated to stop the supply amount of the gas fuel. During the operation of the second operation, the step of transitioning to the second operation using both gaseous fuel and liquid fuel as fuel by lowering the pressure to a predetermined value and starting the regulation control of the liquid fuel supply amount. Returning the first operation by terminating the regulation control of the liquid fuel supply amount and reducing the liquid fuel supply amount and starting the gas fuel supply amount regulation control. I assume.
In the present invention, at the time of transition from the first operation to the second operation, the control of the supply amount of gaseous fuel is ended and the control of the supply amount of liquid fuel is started, and the supply of gaseous fuel is started. Reduce the amount to a predetermined value. The operation to reduce the supply amount of the gaseous fuel to a predetermined value is performed in a very short time, for example, within about 1 second. When the supply amount of the gaseous fuel decreases, the control control of the liquid fuel increases the supply amount of the liquid fuel so as to maintain the target rotational speed of the engine. Therefore, the transition from the first operation to the second operation is performed without significantly affecting the rotational speed of the engine.
When returning from the second operation to the first operation, the control of the supply amount of liquid fuel is terminated and the control of the supply amount of gaseous fuel is started, and the supply amount of liquid fuel is Continuously lower. When the liquid fuel supply amount is continuously reduced, the gas fuel supply amount is increased to maintain the target rotational speed of the engine by the action of the gaseous fuel control. Therefore, the return from the second operation to the first operation is performed without significantly affecting the rotational speed of the engine.

Preferably, the step of returning to the first operation is performed in the process of reducing the output of the engine.
By performing the step of returning to the first operation in the process of decreasing the output of the engine, it is easy to return to the first operation in a short time. At the time of return to the first operation, the occurrence of knocking and misfires is an issue, but in the process where the engine output decreases, it is easy to maintain an appropriate air-fuel ratio because a sufficient amount of air is maintained. In terms of speed control, the fuel supply is limited, so rapid increase in gaseous fuel can be suppressed, and knocking and misfires are less likely to occur. Therefore, by performing the return to the first operation according to this timing, it is possible to return in a short time while maintaining appropriate combustion.

Further, in the step of returning to the first operation, the step of reducing the liquid fuel supply amount includes a first step of reducing the liquid fuel supply amount at a relatively high speed and a second step of reducing the liquid fuel supply amount at a relatively low speed. It is preferable to have
When the mechanical fuel injection pump is used to supply the liquid fuel, the second stage corresponds to the non-injection region of the mechanical fuel injection pump, and the liquid fuel is not substantially injected.

Also, the step of returning to the first operation is performed when the engine output enters the lower region of the assist off-line set in the range of ± 10% with respect to the marine cubic characteristic line, and the second operation is performed. The step of transitioning to may be performed when the output of the engine enters the upper region of Assist On-line set above Assist Off-line.
Here, the assist off-line is set to an output range of ± 10% with respect to the marine cubic characteristic line, and the first operation is performed when the output of the engine enters the lower area (assist off area) of the assist off-line. Return to Further, the assist on-line is set on the upper side of the assist off-line, and when the output of the engine enters the upper area (assist on-on area) of the assist on-line, the operation shifts to the second operation.

In the step of shifting to the second operation, the supply amount of gaseous fuel is set to a larger value as the output of the engine is larger.
Even in the region where the output of the engine is large, the second operation can be quickly returned to the first operation.

The present invention is an operating method of an engine, comprising the steps of: performing a second operation using both gaseous fuel and liquid fuel subjected to temperature control as fuel; and terminating liquid fuel speed control in this step And d) continuously reducing the supply amount of the liquid fuel and performing the first operation of controlling the gas fuel as a major part of the heat source and performing the speed control.
The operating method of the engine of the present invention can quickly shift from the second operation to the first operation.

The present invention is an operating method of an engine, wherein a gas fuel is used as a major part of a heat source to control gas fuel, and a gas fuel and a liquid fuel are used as fuel to control a liquid fuel. The engine is operated by selectively switching one of the assist mode and the diesel mode in which the speed control is performed using only liquid fuel as fuel, and the output of the engine during the operation in the assist mode is a marine cubic characteristic line. Transition to the gas mode when entering the assist-off region set along the path, and transition to the assist mode when the engine output enters the assist-on region where the output is higher than the assist-off region during operation in the gas mode It is characterized by

According to the present invention, since the return from the assist mode to the gas mode can be quickly performed, the transition of the operation mode between the gas mode and the assist mode can be steadily performed at any time and rapidly under the condition corresponding to the output of the engine. And return. As a result, occurrence of knocking and misfire in the gas mode can be avoided in advance, and the operation in the assist mode is limited to the torque rich region operated at the time of emergency when the output is greatly increased. Are also suitable.
Further, in the operation in the assist mode, it is preferable that an operation parameter to be controlled in the operation of the engine be set in common with the gas mode.

The present invention relates to an engine system, and an operation control unit for controlling the operation of the engine, a gas governor for controlling the supply amount of gaseous fuel, and a diesel governor for controlling the supply amount of liquid fuel. During the first operation where the operation control unit uses the gaseous fuel as the major part of the heat source, the control control of the gaseous fuel by the gas governor is ended to reduce the supply amount of the gaseous fuel, and the diesel governor Start control of the liquid fuel by the control unit to shift to the second operation using both gaseous fuel and liquid fuel as fuel, and finish the control control of liquid fuel by the diesel governor during the second operation Then, while reducing the supply amount of the liquid fuel, the present invention is characterized in that the control operation of the gaseous fuel by the gas governor is started to return to the first operation.
In the present invention, when transitioning from the first operation to the second operation by the operation control unit, the control of the supply amount of the gaseous fuel by the gas governor is ended and the supply amount of the gaseous fuel is reduced to a predetermined value. Start the control control of the liquid fuel supply amount by. The operation of reducing the supply amount of gaseous fuel to a predetermined value is performed in a very short time, for example, within about 1 second. When the supply amount of the gaseous fuel decreases, the control control of the liquid fuel increases the supply amount of the liquid fuel so as to maintain the target rotational speed of the engine.
When returning from the second operation to the first operation, the control of the amount of liquid fuel supplied by the diesel governor is terminated and the amount of liquid fuel supplied is continuously reduced, and the amount of gaseous fuel supplied by the gas governor Start the speed control of When the liquid fuel supply amount is reduced, the gas fuel supply amount is increased to maintain the target rotational speed of the engine by the action of the gaseous fuel control. Therefore, the transition and return between the first operation and the second operation can be implemented without significantly affecting the rotational speed of the engine.

According to the engine operation method and the engine system according to the present invention, the first operation and the second operation can be switched mutually, and moreover, when transitioning from the first operation to the second operation, the second operation When returning from the operation to the first operation, each transition can be smoothly performed in a very short time, and the rotational speed of the engine is not significantly affected.
In addition, since the occurrence of knocking and misfire can be avoided beforehand in the first operation, and the second operation is limited to the torque rich region operated at the time of non-steady state, it is suitable also from the environmental countermeasure side by exhaust gas regulation.

It is a block diagram showing the important section composition of the marine dual fuel engine by the embodiment of the present invention. It is a figure which shows the diesel mode in a dual fuel engine. It is a figure which shows the gas mode in a dual fuel engine. It is a figure which shows the assist mode in a dual fuel engine. It is a three-dimensional map which shows the relationship between an output, a rotational speed, and a VIVT command value. It is a three-dimensional map which shows the relationship between an output, a rotational speed, and the valve closing timing of an inlet valve. It is a graph which shows the relationship between an output and the optimal VIVT command value in the case where the rotational speed of an output shaft is constant, and when changing. It is a graph which shows the relationship between the valve opening timing of a fuel gas supply valve, and THC concentration in, when the VIVT command value changes variously. It is a graph which shows the relationship between an output and the valve-opening timing of a fuel gas supply valve in, when the rotational speed of an output shaft is constant and changes. It is a graph which shows the fuel gas supply start time corresponding to VIVT command value. It is a figure showing composition of a control device which performs PID control of a marine dual fuel engine. It is a figure which shows the process of performing PID control so that real rotation speed may turn into target rotation speed in a gas governor. FIG. 6 is a diagram showing a process of performing PID control so that an actual rotation speed becomes a target rotation speed in a diesel governor. It is a timing chart of the opening-and-closing operation of the suction valve and the fuel gas supply valve in the time of a normal time and an advance angle. It is a graph which shows the relationship between a marine cube characteristic line, an assist on area | region, and an assist off area | region. It is a graph which shows the output and governor command value at the time of transfer from gas mode to assist mode. It is a graph which shows the output at the time of return from assist mode to gas mode, and a governor command value. FIG. 1 is a flow chart of a normal cycle of a combustion cycle of an engine. It is process drawing of the mirror cycle of the combustion cycle of an engine. It is a figure which shows the conventional variable intake valve timing mechanism.

First, a variable intake valve timing (VIVT) mechanism will be described as a dual fuel engine according to the present invention.
That is, the present inventors change the opening (supply start) timing of the fuel gas supply valve at each VIVT angle, determine the optimum value from the THC concentration and the combustion state, and the fuel gas supply valve according to the VIVT angle. By setting the valve opening timing, it is possible to suppress the knocking that occurs when raising the output of the gas fuel engine and shorten the load raising time, and further, the fuel gas supply valve in the torque rich region and torque poor region. It has been found that combustion fluctuation and rotational speed hunting that were attributable to the valve opening timing of the valve can be improved.

As an engine knocking suppression technique, a variable intake valve timing (VIVT) mechanism can be used to lower the effective compression ratio. A knocking suppression technique will be described with reference to FIGS. 16A and 16B in this regard. FIG. 16A shows the process of a normal four-stroke cycle, and FIG. 16B shows the process of a mirror cycle.

For example, in a gas fueled engine, the intake valve typically closes to the bottom dead center of the piston (see FIG. 16A). On the other hand, when the timing of closing as shown in FIG. 16B faster than the bottom dead center, because the expansion of the mixture continue after closing of the intake valves, cylinder temperature Ts falls below the case of FIG. 16A (Ts * ^<Ts) . Since the maximum compression temperature at the top dead center is also reduced by that amount (Tc ^* <Tc), self-ignition can be prevented and knocking can be suppressed.
As a drawback of the Miller cycle, the compression temperature drops and the ignitability in the low load area deteriorates, so at the time of start-up or low load, the normal intake valve opening timing shown in FIG. It is necessary to make the valve opening timing earlier.

Hereinafter, as an engine according to an embodiment of the present invention, for example, a 4-stroke dual fuel engine 1 used for a marine engine will be described based on the attached drawings.
The marine dual fuel engine 1 (hereinafter sometimes referred to simply as the engine 1) shown in FIGS. 1 and 2 can be switched to one of the diesel mode D, the gas mode G, and the assist mode As during operation. The dual fuel engine 1 shown in FIG. 1 includes a mechanism of a crankshaft 2 as an output shaft connected to a propeller or the like, and the crankshaft 2 is connected to a piston 4 installed in a cylinder block 3. A combustion chamber 6 is formed by the piston 4 and the engine head 5 provided in the cylinder block 3.

The combustion chamber 6 is sealed by an intake valve 8 and an exhaust valve 9 mounted on the engine head 5 and a fuel injection valve 10 used in the diesel mode D. The engine head 5 is provided with a micro pilot oil injection valve 11 used in the gas mode. A fuel injection pump 12 is connected to the fuel injection valve 10. An intake pipe 13 is connected to an intake port where the intake valve 8 of the engine head 5 is installed, and an exhaust pipe 14 is installed at an exhaust port where the exhaust valve 9 is installed. The intake pipe 13 is provided with a fuel gas supply valve 15 consisting of a solenoid valve for controlling gas injection, and on the upstream side thereof, an air cooler 16 and a turbocharger 17 communicating with the exhaust pipe 14 are provided.

Here, as shown in FIGS. 2A, 2B, and 2C, the dual fuel engine 1 according to the present embodiment can be switched between the diesel mode D, the gas mode G, and the assist mode As. In the diesel mode D shown in FIG. 2A, for example, fuel oil A is supplied as a fuel oil from a fuel tank (not shown) to the fuel injection pump, and mechanically injected from the fuel injection valve 10 into compressed air in the combustion chamber 6 for ignition. It can be burned.

In the gas mode G shown in FIG. 2B, fuel gas such as natural gas is supplied to the intake pipe 13 by the fuel gas supply valve 15 to be premixed with the air flow, and the mixture is supplied into the combustion chamber 6, Ignition is performed by the igniter in a compressed state, and in this example, pilot fuel is injected from the micro pilot oil injection valve 11 to be ignited and burned. The micro pilot oil injection valve 11 is electronically controlled, for example, and injects a small amount of pilot fuel as a powerful ignition source. The fuel gas supply valve 15 is a solenoid valve that can form a large opening with a slight stroke and allow a large amount of gas to flow in a short time.
In the assist mode As shown in FIG. 2C, fuel oil is injected from the fuel injection valve 10 into the combustion chamber 6 by speed control, and fuel gas is supplied from the fuel gas supply valve 15 into the intake pipe 13.

The gas mode G is an operation mode in which ignition is performed by a spark plug using only gas fuel (gas fuel) as fuel, and injection of a small amount of liquid fuel (pilot oil) for ignition of gas fuel which occupies most of the heat source. It includes both modes of operation used. The proportion of liquid fuel in the total fuel in the latter mode of operation is usually about 1% to 10% of the total heat in comparison with the heat of rated output. From the viewpoint of achieving environmental regulations on exhaust gas, it is desirable to be 3% or less.
The assist mode As is an operation mode in which both the gas fuel and the liquid fuel are used as fuel, and furthermore, the regulation control of the supply amount of the liquid fuel is performed. In the assist mode As using liquid fuel, it is preferable to minimize the operation time from the viewpoint of environmental protection, and to immediately return to the gas mode when the assist mode is not necessary. In the assist mode As, fuel oil is injected from the fuel injection valve 10 into the combustion chamber 6 for combustion, and pilot fuel is also injected from the micro pilot oil injection valve 11 into the combustion chamber 6 for combustion.
The diesel mode D is mainly used at the start and stop of the engine, and is an operation mode in which operation is performed using only liquid fuel as fuel.

The engine 1 is started in a diesel mode D in which liquid fuel is injected into the combustion chamber 6 from the fuel injection valve 10. After it is confirmed that the gas pressure above the reference value is supplied to the engine 1, the gas fuel is supplied to the intake pipe 13 by the fuel gas supply valve 15, mixed with air, and then flowed into the combustion chamber 6. , And operate in gas mode G for burning gas fuel.
At the time of a stop, it changes to diesel mode D again, and stops. The diesel mode D and the gas mode G can be changed except at the time of start and stop.

In the steady operation, the engine 1 is operated in the gas mode theoretically along the ship cubic characteristic line due to the relationship between the rotational speed and the output. The marine cubic characteristic refers to the characteristic of the main marine engine (engine 1) whose output is proportional to the cube of the rotational speed in a ship using a fixed pitch propeller. If the ship maneuvers during stormy weather or other maneuvers such as a rapid course change other than steady-state operation are performed, the output over the normal operation range is required far beyond the marine cubic characteristic, and in gas mode G In the operation of the above, the liquid fuel may be temporarily supplied into the combustion chamber 6 and the operation may be performed in the assist mode As together with the gaseous fuel because the operation may be difficult due to insufficient output. Operation in the assist mode As is processed within the necessary minimum time in consideration of environmental impact in order to use the liquid fuel in the speed control, and if the assist mode As is not necessary, the gas is swiftly It is desirable to return to mode G.

The dual fuel engine 1 according to the present embodiment includes a gas engine system that performs output control when the load increases in the gas mode G. The structure of this gas engine system will be described.
In FIG. 1, a rotational speed sensor 20 and a torque sensor 21 are attached to the crankshaft 2. The rotational speed sensor 20 measures the rotational speed (rotational speed) of the crankshaft 2. measure. As the torque sensor 21, for example, a sensor that detects torque applied to the shaft by strain can be used. Measurement data measured by the rotational speed sensor 20 and the torque sensor 21 are respectively output to the control unit 22 that controls the engine 1.

The control unit 22 detects the operating state of the engine 1 based on signals from the rotational speed sensor 20 and the torque sensor 21 or the like. That is, assuming that the rotational speed (rotational speed) of the crankshaft 2 measured by the rotational speed sensor 20 is n, and the torque measured by the torque sensor 21 is T, the output of the engine 1 by the following equations (1) and (2) (Load) Calculate A. However, Lt is the rated output of the engine 1.
Output Lo = 2πTn / 60 (1)
Output (load) A = Lo / Lt × 100 (2)

As a method of obtaining the output (load) of the engine 1, a method of inferring from the information regarding the amount of fuel supply and other operating conditions of the engine 1, and providing a torque sensor 21 in the power transmission system of the output shaft of the engine 1, There is a method of actually measuring the torque and determining the output. In a gas fueled engine, since the gas to be a fuel is an elastic body, it is relatively difficult to obtain an accurate supply amount of fuel as compared to a liquid fuel. Therefore, it is preferable to calculate the output by actually measuring the torque with the torque sensor 21.
When the rotational speed n is fixed, the output A and the torque measurement value T are in direct proportion. Under the condition that the rotational speed n is constant, it is desirable to set the advancing timing of the closing timing of the intake valve 8 at a larger rate as the output A is larger, that is, as the torque data T is larger.

The control unit 22 stores a first map 24 for determining a first electric signal of intake valve opening / closing timing created in advance, and a second map 25 for determining a second electric signal from the first electric signal and opening / closing timing. There is. In the control unit 22, based on the rotational speed data n and the torque data T corresponding to the output A of the engine 1 measured by the rotational speed sensor 20 and the torque sensor 21, the engine 1 is obtained by the equations (1) and (2). Calculate output A. The first electric signal corresponding to the opening / closing timing of the intake valve 8 is selected in the first map 24 based on the rotational speed n and the output A. Based on the first electric signal, the second map 25 determines the open / close timing of the intake valve 8 corresponding to the first electric signal. The method of creating the first map 24 and the second map 25 will be described later.
The second electrical signal of the open / close timing set by the control unit 22 is transmitted to the electro-pneumatic converter 27, and the electro-pneumatic converter 27 converts the signal of the open / close timing into air pressure. This air pressure is sent to the actuator 28 to control the drive of the variable intake valve timing mechanism 30. The actuator 28 is supplied with air pressure P1, P2 for driving and control from the first pressure reducing regulator 34 and the electropneumatic converter 27.

The air pressure supplied to the actuator 28 is compressed by the air compressor 32 and stored in the air tank 33. The air pressure in the air tank 33 is reduced by the first pressure reduction regulator 34 to a necessary pressure. The pressure at this time is adjusted by changing the valve opening of the first pressure reducing regulator 34, and is supplied to the actuator 28 as the air pressure P1 for driving. If the pressure P1 measured by the pressure gauge 36 is less than the specified value, the engine 1 can not be started.
The air pressure for driving the electro-pneumatic converter 27 is further reduced from the first pressure reduction regulator 34 by the second pressure reduction regulator 37 and supplied. The electro-pneumatic converter 27 supplies the air pressure corresponding to the inputted second electric signal of the open / close timing to the actuator 28 as the air pressure P2 for adjusting the operation of the actuator 28. Based on these air pressures P1 and P2, the rod 28a of the actuator 28 is operated to operate the variable intake valve timing mechanism 30.

The actuator 28 is, for example, a known P cylinder (a cylinder with a positioner), and controls the advancing and retracting of the rod 28 a based on the pressures P1 and P2 input from the first pressure reducing regulator 34 and the electropneumatic converter 27. By changing the moving length of the rod 28a of the actuator 28, the drive of the variable intake valve timing mechanism 30 is controlled to advance (advance) or delay the timing of closing the intake valve 8 from the suction bottom dead center (late Control to reduce the compression ratio.
Since the time between the valve opening timing and the valve closing timing of the intake valve 8 does not change, when the valve opening timing advances from the suction bottom dead center, the valve closing timing also advances from the suction top dead center by the same time. Moreover, in the present embodiment, the timing of valve opening and valve closing is changed according to the output of the engine 1 to suppress knocking and shorten the load increase time. The opening / closing timing of the intake valve 8 is set by the first map 24 and the second map 25 in the control unit 22 based on the output A of the engine 1 and the rotational speed n, and the actuator 28 and the variable intake valve timing mechanism 30 The timing of opening and closing of the valve is adjusted to suppress knocking.

The configuration of the variable intake valve timing mechanism 30 is conventionally known, and has the same configuration as that shown in FIG. That is, in the variable intake valve timing mechanism 30, for example, a link shaft whose rotation angle range is set by the movement length of the rod 28a of the actuator 28 and a cam shaft provided with an eccentric cam are disposed in parallel. An exhaust swing arm is connected to the link shaft, and an intake swing arm is connected to a tappet shaft provided at an eccentric position of the link shaft. An intake valve 8 is connected to the intake swing arm, and an exhaust valve 9 is connected to the exhaust swing arm.

The distance between the cam shaft and the intake swing arm changes according to the rotation angle of the tappet shaft according to the rotation of the link shaft, and the timing at which the eccentric cam of the cam shaft starts to change changes. As a result, the valve closing timing can be changed to an advance angle (or a delay angle). As the distance from the tappet shaft to the cam shaft center increases, the closing timing of the intake valve 8 becomes earlier. The rotation angle of the tappet shaft is changed by the moving length of the rod 28 a of the actuator 28. The moving length of the rod 28a is arbitrarily changed by the pressure P1, P2 of the control air supplied to the actuator 28.
The magnitude of the advance angle which is the closing / opening timing of the intake valve 8 is determined by the timing at which the eccentric cam of the camshaft starts to hit the intake swing arm connected to the tappet shaft of the link shaft.

The apparatus for rotating the tappet shaft in the variable intake valve timing mechanism 30 may use a servomotor (not shown) instead of the actuator 28. In this case, the signal of the opening / closing timing transmitted from the second map 25 of the control unit 22 is input to the servomotor. The servomotor rotates the link shaft by an amount corresponding to the received signal to turn the tappet shaft, thereby making it close to and separated from the cam shaft, and the opening / closing timing of the intake valve 8 can be changed. When a servomotor is used, the configuration of the actuator 28 and the air compressor 32 to the pressure gauge 38 is unnecessary. Also, instead of the electro-pneumatic converter 27, the controller drives a servomotor.

Further, a mechanism for supplying gas fuel to the fuel gas supply valve 15 that controls gas injection to the intake pipe 13 will be described. In FIG. 1, gas fuel is supplied to the gas vaporizer 41 from an LNG gas tank 40 in which gas fuel such as natural gas is stored, and the gas pressure is further reduced by the gas regulator 42 to a necessary gas pressure.
The gas pressure is displayed on the fuel gas pressure gauge 43, adjusted by changing the valve opening of the gas regulator 42, and supplied from the fuel gas supply valve 15 into the intake pipe 13 as gaseous fuel for combustion. In the intake pipe 13, the gas fuel and the supercharged air cooled by the air cooler 16 are mixed and supplied to the combustion chamber 6. When the load is increased, the amount of gas fuel supplied is increased by the operation of the fuel gas supply valve 15.

The second electrical signal of the open / close timing set by the control unit 22 is transmitted to the fuel gas supply valve 15 via the gas governor 44 separately from the electropneumatic converter 27. The gas governor 44 controls the speed of the supply of gas fuel in the gas mode (governor control). In addition, the gas governor 44 controls the opening timing of the fuel gas supply valve 15 to open the fuel gas supply valve 15 to supply the gas fuel into the intake pipe 13 in accordance with the advance angle of the closing timing of the intake valve 8. The gas regulator 42 for adjusting the gas pressure and the gas governor 44 for advancing the opening timing of the fuel gas supply valve 15 and performing the speed control are included in the fuel gas supply valve timing mechanism 45.
The gas governor 44 may be installed outside the control unit 22. If the fuel gas supply valve timing mechanism 45 can receive the second electric signal from the second map 25 and advance the opening timing of the fuel gas supply valve 15 according to the advancing angle of the closing timing of the intake valve 8 Good.

Furthermore, the control unit 22 is provided with a diesel governor 48 that performs control of liquid fuel control in the assist mode As. The diesel governor 48 receives the second electrical signal of the open / close timing and supplies it to the fuel injection pump 12 to control the amount of fuel oil injected from the fuel injection valve 10 into the combustion chamber 6. The diesel governor 48 may be installed outside the control unit 22.
The diesel governor 48 controls the liquid fuel in the assist mode As and controls the supply amount of the liquid fuel so as to match the target rotational speed of the engine 1. When returning from the assist mode As to the gas mode G, the control control of the liquid fuel is ended.
The control unit 22 has a configuration including the first map 24 and the second map 25 as an operation control unit 49, and has a gas governor 44 and a diesel governor 48 separately from the operation control unit 49.

Next, a method of creating the first map 24 and the second map 25 stored in the control unit 22 will be described. FIG. 3 shows the crank angle when the intake valve 8 is closed, which is the VIVT command value (intake valve closed crank angle, Intake Valve Closed timing, IVC) by the rotational speed of the crankshaft 2 and the output (load factor) of the engine 1 It is a three-dimensional map which shows the detail of the 1st map 24 to determine.

In FIG. 3, the region B in which the operation is carried out regularly (practical) is indicated by a broken line. On the other hand, the change (advance angle) of the VIVT command value with respect to the change of the output when the rotational speed performed in the power generation is constant is shown by the arrow line C, and the rotational speed and the output (load factor) The change (advance angle) of the VIVT command value in the case of simultaneously changing is indicated by an arrow line D. An arrow line D indicates a marine cube characteristic. The marine cubic characteristic represents a typical characteristic of a marine main engine whose output is proportional to the cube of the rotational speed, and is a characteristic curve of the rotational speed and the output determined by the rated rotational speed of the engine and the rated output. The region where the output (load factor) is higher than the marine cubic characteristic line D in the region of the ordinary operation region B indicates a torque rich region, and the region where the output (load factor) is low indicates a torque poor region.

The first map 24 was created based on the steps of the following experimental procedures (1) to (18).
In the experiment, the same type of dual fuel engine 1 actually used was used.
(1) Start the engine 1 and set the rotational speed (rotational speed) n to 400 min ^-1 , the output (load) A to 10%, and the intake valve 8 closing timing to 545 deg (the latest closing timing). Set
(2) The abnormal combustion called knocking generated when driving the engine 1 and the exhaust temperature at that time are measured. The knocking is detected by a knock sensor (not shown) attached to each engine head 5. When the knocking phenomenon occurs, the normal combustion waveform is a waveform in which high-frequency pressure fluctuations overlap.

Further, the exhaust temperature at the time of knocking measurement is measured by a temperature sensor attached to the exhaust pipe 14.
(3) After the measurement of the exhaust gas temperature at the time of knocking measurement is completed, the valve closing timing of the intake valve 8 is decreased by 5 deg, and the measurement of (2) is performed again. Measurement is performed by changing the valve closing timing up to 500 deg (structurally, the earliest valve closing timing).
(4) When the measurement of the above (3) is finished, the output A is gradually increased by 10% to 110% and the measurements of (2) and (3) are repeated again.

(5) According to the measurements (1) to (4), when the knocking strength is equal to or less than the reference value and the exhaust temperature is 500 ° C. or less, knocking is suppressed and the engine 1 can be operated safely. I will judge.
(6) From the measurement result of (5), in the three-dimensional graph of FIG. 4 in which the X axis is output A, the Y axis is rotation speed n, and the Z axis is open / close timing, ● (black circle), plot x at unsafe measurement points. By this, it is possible to select the knocking suppression range in the relationship among the output A, the rotational speed n and the valve closing timing.
(7) a measuring step of the above (1) to (6), the rotational speed n rises to 900 min ^-1 by 100 min ^-1, measured safely driving can range for each rotation speed n.

(8) The graph which represented the measurement result of said (7) by three axes | shafts of rotational speed n, output A, and valve closing timing is FIG. In FIG. 4, the range enclosed by the straight line is a range in which knocking is suppressed and the engine 1 can be operated safely.
(9) Nitrogen oxides (hereinafter referred to as NOx) have a reference value within the range of a three-dimensional area surrounded by a straight line where the engine can be operated safely as shown in FIG. 4 measured by the experiments of (1) to (8) above. Further experiments will be conducted to find the setting with the highest thermal efficiency.
The engine rotational speed n is set to 400 min ^-1 , the output A is set to 10%, and the closing timing of the intake valve 8 is set to 545 deg.

(10) Next, measure NOx and thermal efficiency. NOx is measured by an exhaust gas analyzer attached to the exhaust pipe 14. The thermal efficiency is calculated by the following equation (3) from the fuel flow rate L measured from the fuel flow meter attached to the fuel pipe and the output A calculated from the measurement result of the torque sensor 21.
Thermal efficiency η = 360Lo / H / L (3)
However, H: Lower calorific value of fuel gas (J / Nm ³ )
Lo: Current output L: Fuel flow rate

(11) After completion of the measurement of (10), the valve closing timing of the intake valve 8 is decreased by 5 deg each, and the measurement of (10) is performed again. The valve closing timing changes to 505 deg and performs measurement (see FIG. 9).
(12) When the measurements of (10) and (11) are finished, the output is increased stepwise to 110% by 10%, and the measurements of (10) and (11) are repeated again. The valve closing timing is changed within the safe operation range shown in FIG.

(13) the measurement of the (9) to (12), the rotational speed n rises stepwise to 900 min ^-1 by 100 min ^-1, to determine a good measurement point most performance for each rotational speed.
(14) The valve closing timing of the intake valve 8 is set for each rotational speed n and output A, where NOx is equal to or less than the predetermined value and the thermal efficiency is the highest. As a result of this, a draft of the first map shown in FIG. 3 is created.

(15) The rotational speed n and the output A are increased in an arbitrary load raising pattern to detect knocking. The load raising pattern is a change state of output A (load factor) and rotational speed n per time, and changes according to propeller specifications (shape, rotation number) of the marine propulsion device.
(16) The valve closing timing of the measurement point at which the knocking intensity detected in (15) is equal to or greater than the reference value is decreased by 3 deg.
(17) The steps (15) and (16) are repeated until the knocking strength falls below the reference value to determine the valve closing timing at which knocking is suppressed. If the valve closing timing is reduced, the thermal efficiency will deteriorate. The setting values of the valve closing timing at which NOx and knocking strength are lower than the reference value and the result of the highest thermal efficiency is obtained are set as rotational speed n and output A.
(18) The valve closing timing at which knocking was suppressed from (17) above was measured at each rotational speed n and output A, and a final first map 24 shown in FIG. 3 was created from the results.

In FIG. 3, a VIVT command value corresponding to the rotational speed and the output is shown by a graph of a three-dimensional plane, and the upper side in the drawing is the direction in which the valve closing timing is advanced. On the three-dimensional plane, a region indicated by a broken line is a practical operation region used in the actual operation of the ship propulsion device, and one example of a good load raising pattern is indicated by a marine cubic characteristic line D. In load increase in a practical operation area, control is performed to increase the advance angle of the valve closing timing as the engine output increases.
In one example of a good load raising pattern shown by the marine cubic characteristic line D, the advance angle is minimized at the lower right position in the drawing where the rotational speed and output are small, and the advance angle is increased as the rotational speed and output increase. Do. Although the ratio of increasing the advance angle is not constant, the advance angle is increased as the output as a whole increases. Since the output (load factor) is determined by the product of the torque and the rotational speed, it can be expressed that the advance angle is increased as the torque of the output shaft increases.

Next, a second map 25 was created in the following experiment.
When the variable intake valve timing mechanism 30 is rotationally controlled by the actuator 28, the second map 25 is created in the following procedure.
(1) The valve closing timing is changed by the actuator 28, and the pressure when changing to each valve closing timing is measured.
(2) From the specifications of the electro-pneumatic converter 27, the second electric signal necessary to supply the pressure of the above (1) is investigated.
(3) From the results of the above (1) and (2), the second map 25 showing the first electric signal selected in the first map 24 on the horizontal axis and the valve closing timing (second electric signal) on the vertical axis create.

The above description is for the case where the actuator 28 is used, and in the case where the variable intake valve timing mechanism 30 is controlled to rotate by a servomotor instead of the actuator 28, the following description will be made.
(1) The valve closing timing is changed based on the servomotor, and the second electric signal at the time of changing each valve closing timing is measured.
(2) A second map 25 indicating the first electric signal on the horizontal axis and the valve closing timing (second electric signal) on the vertical axis is created based on the result of the above (1).
The second map 25 is a map that represents the relationship between the valve closing timing (second electrical signal) and the first electrical signal.

In the three-dimensional map shown in FIG. 3, the optimum VIVT command value differs depending on the output between the power generation characteristic line indicated by the solid line C and the marine cubic characteristic line D. That is, as shown in FIG. 5 as an example, even when the output is the same, when the rotational speed is different, the intake valve closing crank angle of the optimum VIVT command value is different.
In this embodiment, to the exhaust pipe 14 of unburned fuel gas at the time of valve overlap of the intake valve 8 and the exhaust valve 9 corresponding to the change of the VIVT command value, that is, for various intake valve closing crank angles. The opening timing of the fuel gas supply valve 15 for supplying the fuel gas to the intake pipe 13 is set so that the blow through of the valve is reduced. For this purpose, first, a VIVT command value corresponding to the rotational speed and the output is set. Strictly speaking, it is preferable to set the air-fuel ratio and ignition timing to optimum values using thermal efficiency and NOx as a standard, but here, these conditions are not set as the engine 1 can be operated stably. .

As an example of setting the valve opening timing of the fuel gas supply valve 15, how to determine the valve opening timing of the fuel gas supply valve 15 by the gas governor 44 under the engine operating condition according to the optimum VIVT command value in the marine cubic characteristic line D is described below. Explain to.
First, under each operating condition where the engine output (load factor) is 25%, 50%, 75% and 100%, the fuel gas is supplied from the fuel gas supply valve 15 using the timing at which the intake valve 8 opens as a standard. Since the fuel gas is supplied into the intake pipe 13, the fuel gas does not reach the intake valve 8 instantaneously. Therefore, the crank angle position of the valve opening timing of the fuel gas supply valve 15 in consideration of the distance from the fuel gas supply valve 15 to the intake valve 8 is assumed. Then, the crank angle position at the valve opening timing of the fuel gas supply valve 15 is changed in 5 deg intervals before and after, and the total hydrocarbon concentration (unburned gas in the exhaust gas at the gas turbine outlet of the turbocharger 17 at that time) Measure THC concentration). Measurement of THC concentration is repeated and performed under each operating condition. The THC concentration is preferably measured by hydrogen flame ionization method (JIS B 7956).

The opening timing of the fuel gas supply valve 15 is changed according to each condition, and each VIVT command value (intake valve closing crank angle) is set to, for example, 40%, 65%, 85%, 100%, and each VIVT FIG. 6 shows the relationship between the fuel gas valve opening timing and the measured THC concentration at the command value.
As shown in FIG. 6, the opening timing of the fuel gas supply valve 15 is based on the crank angle at which the unburned fuel gas blows little at the time of valve overlap and the THC concentration becomes the lowest. On the other hand, when the valve opening timing of the fuel gas supply valve 15 changes rapidly due to the output change, it leads to the above-mentioned combustion fluctuation and rotation speed fluctuation. For this reason, ± 5 deg. From the selected reference so that the change amount of the valve opening timing of the fuel gas supply valve 15 according to the output has a small inclination as much as possible. C. The crank angle which becomes the fuel gas valve opening timing of the fuel gas supply valve 15 in the range of A is selected, and the crank angle corresponding to the valve opening timing of the fuel gas supply valve 15 which is optimum in each condition is determined.

The relationship between the crank angle at the valve opening timing of the fuel gas supply valve 15 and the output (load factor) at the optimum VIVT command value of the marine cubic characteristic line D determined in this manner is shown in FIG. Change "is shown by a broken line.
Similarly, the relationship between the crank angle at the valve opening timing of the fuel gas supply valve 15 and the output (load factor) at the optimum VIVT command value at the constant rotational speed output performed on the power generation characteristic line C of FIG. Is indicated by a broken line of “constant rotation speed” in FIG.
As shown in FIG. 7, the optimal valve opening timing of the fuel gas supply valve 15 is different between the condition in which the rotational speed changes and the condition in which the rotational speed is constant even if the output is the same.

However, the crank angle of the opening timing of the optimum fuel gas supply valve 15 at the optimum VIVT command value of the marine cubic characteristic line D and the optimum fuel gas at the optimum VIVT command value of the power generation characteristic line C (constant rotational speed) As shown in FIG. 8, the crank angle of the valve opening timing of the supply valve 15 exhibits one coincident linear characteristic when arranging the VIVT command value on the horizontal axis instead of the output. That is, it is understood that the valve opening timing of the optimum fuel gas supply valve 15 does not depend on the output but depends on the specified VIVT value (intake valve closing crank angle).

As apparent from FIG. 8, when the closing timing of the intake valve 8 is changed by the variable intake valve timing mechanism 30, the advancing of the supply start timing of the fuel gas supply valve 15 advances as the advancing timing of the closing timing of the intake valve 8 advances. The degree of corners is greater.
Therefore, by setting the crank angle of the optimal valve opening timing of the fuel gas supply valve 15 determined under each condition by the gas governor 44 based on the VIVT command value, the fuel gas supply valve 15 is opened according to the VIVT command value. Timing can be optimized. In FIG. 8, the unmeasured VIVT command value, the fuel gas supply start timing, etc. may be determined by an approximate line connecting data before and after the measurement point.

Next, timing control of the fuel gas supply end by the fuel gas supply valve 15 will be described with reference to FIGS.
FIG. 9 shows the main configuration of the engine 1 shown in FIG. In FIG. 9, a target rotational speed command unit 50 is installed outside the control unit 22, and a preset target rotational speed is input to the control unit 22. The gas supply time calculation unit 51 of the control unit 22 directly performs PID control of the opening period of the fuel gas supply valve 15 based on the deviation between the actual rotational speed calculated from the measurement value of the rotational speed sensor 20 and the target rotational speed. Do.
The gas supply valve control unit 52 connected to the gas supply time calculation unit 51 calculates the time to open based on the valve opening timing of the fuel gas supply valve 15 and outputs it to the fuel gas supply valve 15 to open it. The feedback control is performed so as to open the fuel gas supply valve 15 only for the time required.
In the control unit 22, rack target value setting means 57 for setting a target position of a control rack (not shown) based on the target rotation speed set by the target rotation speed command unit 50 is disposed. The rack position of the fuel injection valve 10 is feedback-controlled based on the rack position target value set by the rack target value setting means 57.

The valve closing timing control of the fuel gas supply valve 15 is performed as follows. That is, as shown in FIG. 10, in the control unit 22, based on the deviation between the target rotational speed and the actual rotational speed set by the target rotational speed command unit 50, the valve opening period of the fuel gas supply valve 15 is directly PID Control. Specifically, based on the deviation between the target rotational speed and the actual rotational speed, the time during which each fuel gas supply valve 15 is open so that the actual rotational speed follows the target rotational speed by feedback control by the gas governor 44 Control.
The gas supply valve control unit 52 controls the valve closing timing of each fuel gas supply valve 15 based on the valve opening period calculated with the valve opening timing of the fuel gas supply valve 15 as a starting point. The control unit 22 directly performs PID control of the open period of the fuel gas supply valve 15 so that the actual rotation speed matches the target rotation speed without calculating the amount of fuel gas supplied in advance.

The supply pressure control of the fuel gas is a value obtained by adding the air supply pressure detected by the air supply pressure gauge 54 provided in the intake pipe 13 to the pressure ΔP value set using the output of the engine 1 and the data of the rotational speed as parameters. The feedback control of the fuel gas pressure regulator 55 is performed so that the deviation from the value of the fuel gas pressure gauge 43 is eliminated.
Control of the liquid fuel injection pump 12 and the fuel injection valve 10 is performed as follows. That is, as shown in FIG. 11, the control unit 22 directly PID-controls the rack position of the fuel injection pump 12 based on the deviation between the target rotational speed and the actual rotational speed set by the target rotational speed command unit 50. . Specifically, based on the deviation between the target rotational speed and the actual rotational speed, the diesel governor 48 changes the rack position of the fuel injection pump 12 so that the actual rotational speed follows the target rotational speed by feedback control. The injection amount of the liquid fuel injected from the fuel injection valve 10 increases and decreases, whereby the rotational speed of the engine 1 increases and decreases.

FIG. 12 shows the relationship between the advance angle of the variable intake valve timing mechanism 30 and the timing of the start and end of supply of the fuel gas supply valve 15 by the gas governor 44 in which the above result is displayed.
FIG. 12 shows the relationship between the crank angle of the engine 1 and the valve lifts of the intake valve 8 and the exhaust valve 9. The curve showing the opening and closing operation of the intake valve 8 is shown by a solid line when the VIVT (variable intake valve timing) command value is 0%, and by an alternate long and short dash line is when advancing (100% of the VIVT command value). Shows an opening and closing operation image in the case of. Then, the open period of the fuel gas supply valve 15 at the advance angle (the VIVT command value is 100%) becomes longer than the open period of the fuel gas supply valve 15 when the VIVT command value is 0%.

Further, it is preferable to increase the fuel supply amount by increasing the supply pressure of the fuel gas as the closing timing of the intake valve 8 advances. Therefore, in FIG. 9, the supply pressure of the fuel gas into the intake pipe 13 is set to a value obtained by adding the pressure ΔP value to the supply pressure detected by the supply pressure gauge 54 provided in the intake pipe 13. The pressure ΔP is set as data of the outputs and rotational speeds of the plurality of engines 1 measured in advance as parameters. As a result, the supply pressure of the fuel gas supplied from the fuel gas supply valve 15 increases with the advance of the timing at which the intake valve 8 closes.

Next, the relationship between the marine cubic characteristic line, the assist on (ON) region, and the assist off (OFF) region in the operation of the engine 1 controlled by the control unit 22 will be described. In the graph of FIG. 13, the horizontal axis indicates the rotational speed of the engine 1, and the vertical axis is the output (kw).
The marine cubic characteristic line is a characteristic of the marine main engine whose output is proportional to the cube of the rotational speed in a ship using a fixed pitch propeller, and is a basic control output level of the engine 1. However, the relationship between the output and the rotational speed may not be exactly proportional to the third power, but may have a certain degree of deviation. In the figure, the range of plus or minus 10% with respect to the marine cubic characteristic line is indicated by a broken line. The assist off-line is set in the range of this plus or minus 10%. Preferably, the assist off-line is set along the marine cubic characteristic line, and in the present embodiment, as indicated by a long broken line in the figure, as a line along the marine cubic characteristic line slightly above the marine cubic characteristic line. It is set. The area under the assist off-line is regarded as the assist-off area. Also, Assist Online is set above Assist Online. Preferably, the assist on-line is set in accordance with the characteristics of the engine 1 at a level not normally operated above the marine cubic curve. In this embodiment, as shown by the one-dot chain line in the figure, the idle rotational speed to the intermediate rotational speed exceeds the marine cubic characteristic line at a constant rate, and the intermediate rotational speed reaches the rated rotational speed to the marine cubic characteristic line. Set as an approaching line. The upper region of this assist online is the assist on region. In addition, these assist on-line, assist, off-line, etc. show the way of thinking in control, do not mean physical lines, and are preferably implemented as functions in a computer program.

The operation in the gas mode G is steadily performed in the vicinity of the marine cubic characteristic line, but as indicated by the arrow (A), the output may rise temporarily with respect to the rotational speed. When the output rises during the operation in the gas mode G and the assist on region is entered, the operation shifts to the operation in the assist mode As. Thereafter, when the state in which the output rises with respect to the rotational speed disappears, the output decreases to near the marine cubic characteristic line as shown by the arrow (B). When the output falls and enters the assist-off region, the operation returns to the gas mode G.
Since the operation in the assist mode As is limited to the torque rich region where the output is increased, it is also preferable from the viewpoint of environmental measures. Further, in the assist mode As, as indicated by a broken line in the command image of the gas governor in the drawing, control of the gas governor for supplying gaseous fuel of a predetermined value according to the rotational speed is performed.

Next, the operation at the time of transition between the gas mode G and the assist mode As will be described with reference to timing charts shown in FIGS.
FIG. 14 is a timing chart showing an operation at the time of transition from the gas mode G to the assist mode As. The output (load) with respect to the rotational speed is increased when ship maneuvering during rapid weather or maneuvering such as rapid course change is performed. When the output (load) exceeds the preset assist on-line, transition to the assist mode As is made. In this case, the gas governor 44 ends the speed control of the supply amount of gas fuel. Almost simultaneously with this, the control of the supply amount of the liquid fuel is started by the diesel governor 48, and the supply amount of the gas fuel by the gas governor 44 is rapidly reduced to the predetermined value corresponding to the rotational speed described in FIG. Stabilize at low power. The low output gas governor command value changes according to the rotational speed.

The operation of reducing the gas fuel supply amount to a predetermined value is performed in a very short time (for example, within one second). When the supply amount of gas fuel falls to a predetermined value, the supply control amount of the liquid fuel increases the supply amount of the liquid fuel so as to maintain the target rotational speed of the engine 1. As a result, the transition from the gas mode G to the assist mode As is performed without significantly affecting the rotational speed of the engine 1. Similar to the transition to the diesel mode D, the transition from the gas mode G to the assist mode As can be performed in a very short time (for example, within one second) by the gas governor 44 and the diesel governor 48.

Next, referring to FIG. 15, a timing chart showing an operation at the time of returning from the assist mode As to the gas mode G will be described.
During the operation in the assist mode As, when the output (load) with respect to the rotational speed decreases and the output (load) decreases from the preset assist off-line, the gas mode G is restored. When returning from the assist mode As to the gas mode G, the control of the supply amount of liquid fuel is finished by the diesel governor 48, and at the same time, the control of the supply amount of gas fuel is started by the gas governor 44. Moreover, the diesel governor 48 continuously reduces the supply amount of the liquid fuel, for example, to two stages to finally make the amount zero or a very small amount.

The pattern for continuously reducing the amount of liquid fuel supplied by the diesel governor 48 may be linear, curvilinear, or multistage steps having substantially the same function as those described above. It was divided into two steps and lowered linearly. As shown in FIG. 15, in the first stage f1 of the mechanical fuel injection pump 12, the supply amount of liquid fuel is reduced relatively rapidly to reduce the output, and in the area of the second stage f2, the output decreases. To do. It is desirable that the second stage f2 be a non-injection area where substantially no liquid fuel is injected, and that the transition period of the output reduction be reduced slowly. At the boundary between the first stage f1 and the second stage f2, the command of the diesel governor 48 is taken as a governor command at about idle operation.

It is desirable that the operation of continuously reducing the supply amount of liquid fuel by the diesel governor 48 be performed for a long time as compared with the operation of reducing the supply amount of gas fuel described above. The time until the end of the liquid fuel supply by the diesel governor 48 varies depending on the output, but is substantially on the order of several seconds. When the supply amount of the liquid fuel is continuously reduced, the supply control amount of the gas fuel by the gas governor 44 increases the supply amount of the gas fuel so as to maintain the target rotational speed of the engine 1. As a result, the return from the assist mode As to the gas mode G is performed without significantly affecting the rotational speed of the engine 1.

Here, since a predetermined amount of gas fuel is supplied in the assist mode As before returning to the gas mode G, at the time of starting the step of returning to the gas mode G, the speed control of the supply amount of gas fuel is immediately performed. Can be started. Generally, when the gas fuel supply is started from zero, the rise is unstable and it takes time to perform stable control. However, in the assist mode As, since the gas fuel is already continuously supplied at the supply amount of the predetermined value, it is possible to promptly start the speed control of the gas fuel, and follow the speed control after the start. Sex also becomes high.
Therefore, although it differs depending on the output, it is possible to substantially stop the supply of the liquid fuel in a few seconds in the transition from the assist mode As to the gas mode G.

Next, a method of operating the four-stroke dual fuel engine 1 for boat propulsion according to the present embodiment will be described.
When the engine 1 is started, the diesel mode D is started to shift to the gas mode G. In the gas mode G, steady operation is performed on a marine cubic characteristic line. In the control unit 22, the gas governor 44 controls the supply amount of the gas fuel, and in FIG. 13, even if the output is deviated to some extent with respect to the marine cubic characteristic line, the assist on-line is not reached. In the gas mode G, control of rotational speed and output is performed and steady operation is performed. In gas mode G, a mode of operation in which ignition is performed by a spark plug using only gas fuel as fuel, or a mode of operation using injection of a small amount of liquid fuel (pilot oil) for ignition of gas fuel that occupies most of the heat source. It is driven by either. In the case of a mode of operation that contains a small amount of liquid fuel, the proportion of liquid fuel is usually about 1% to 10% of the total amount of heat relative to the amount of heat of rated output, but 3% from the viewpoint of achieving environmental regulations for exhaust gas It is desirable that

In the gas mode G operation, the output (load) of the engine is detected by the rotational speed sensor 20 and the torque sensor 21 provided on the crankshaft 2. The rotational speed sensor 20 measures the rotational speed (rotational speed) of the crankshaft 2, and the torque sensor 21 measures the engine torque. Measurement data measured by the rotational speed sensor 20 and the torque sensor 21 are respectively output to the control unit 22 of the engine 1.
The control unit 22 detects the output of the operating state of the engine 1 based on the signals from the rotational speed sensor 20 and the torque sensor 21 and the like. When the output (load) rises due to acceleration or deceleration of the engine 1 or rough seas and the output (load) exceeds the preset assist online, the gas mode G shifts to the assist mode As (FIG. 14). reference).

At the time of transition from the gas mode G to the assist mode As, the speed control of the gas fuel by the gas governor 44 is finished, the governor command value falls rapidly, and the supply amount of gas fuel drops to a predetermined value. At 48, regulation control of the liquid fuel supply amount is started. The reduction of the gas fuel supply amount is performed in a very short time, for example, within one second. At the same time, the speed control by the diesel governor D increases the amount of liquid fuel supplied so as to maintain the target engine rotational speed. As a result, the gas mode G is shifted to the assist mode As in a short time without largely affecting the rotational speed of the engine. Thereby, knocking and misfiring in the gas mode G can be avoided in advance.
Since operation in assist mode As uses a certain percentage of liquid fuel, operation is performed only for the minimum necessary time from the viewpoint of environmental measures, and when assist mode As is no longer needed, the gas mode is quickly restored. Let

When the output (load) of the engine 1 in the assist mode As is reduced to below the assist off-line, the assist mode As is ended to shift to the gas mode G (see FIG. 15).
When returning from the assist mode As to the gas mode G, the control of the supply amount of liquid fuel is finished by the diesel governor 48, and at the same time, the control of the supply amount of gas fuel is started by the gas governor 44. Moreover, the diesel governor 48 continuously reduces the supply amount of liquid fuel, for example, in two stages, and finally makes the amount zero or a very small amount.

When reducing the supply amount of liquid fuel, the command value of the diesel governor 48 rapidly reduces the supply amount at the first stage f1, and at the second stage f2, the governor command is performed relatively gently with no liquid fuel being injected. Lower the value. The operation of continuously reducing the supply amount of liquid fuel is performed over a long time, for example, several seconds, as compared with the operation of reducing the supply amount of gas fuel at the transition to the assist mode described above.
When the liquid fuel supply amount is continuously reduced, the gas fuel control control by the gas governor 44 rapidly increases the gas fuel supply amount so as to maintain the target rotational speed of the engine 1. Thus, the return from the assist mode As to the gas mode G is performed without significantly affecting the rotational speed of the engine 1.

Moreover, since the predetermined amount of gas fuel is continuously supplied at the stage of the assist mode As, at the time of returning to the gas mode G, it is possible to immediately start the speed control of the gas fuel. Therefore, the speed control of the supply amount of gas fuel can be started promptly, and the followability and stability of the speed control after the start becomes high. Therefore, at the time of transition from the assist mode As to the gas mode G, substantial gas fuel speed control and liquid fuel supply stop or regulation can be performed in a few seconds.

In addition, by performing the step of returning to the gas mode G in the process in which the output of the engine 1 is reduced, the return to the gas mode in a short time becomes easy. When returning to the gas mode, knocking or misfire may occur. However, in the process where the output of the engine 1 is reduced, it is easy to maintain an appropriate air-fuel ratio because a sufficient amount of air is secured.
Moreover, in the process of reducing the output of the engine 1, the regulation control is in the direction of restricting the supply of fuel, so it is possible to suppress the rapid increase of the gas fuel, and knocking and misfiring hardly occur. Therefore, by performing the return to the gas mode G in accordance with the timing of the engine output decrease, it is possible to return to the gas mode G in a short time while maintaining proper combustion. The amount of gas fuel supplied in the assist mode As increases as the output of the engine 1 increases. As a result, even in the region where the output of the engine 1 is large, the return from the assist mode As to the gas mode G can be quickly performed.

Incidentally, in the operation in the gas mode G, the operation of the engine 1 can be continued by shifting from the gas mode G to the assist mode As even in a situation where occurrence of knocking or misfire is expected due to an increase in load. . On the other hand, since a certain proportion of liquid fuel is used in the assist mode As, the operation in the assist mode As is minimized as necessary in terms of environmental protection. Then, when the assist mode As is not required, the operation in the gas mode G is immediately restored.

Since the marine cubic characteristic line indicates the relationship between the output of the engine 1 and the rotational speed, the control of the transition to the assist mode As and the return to the gas mode G Switching based on the relationship and continuity will be performed quickly, and appropriate transition and return will be performed even in the actual maneuvering state where output and rotational speed change in a complex manner. Moreover, since the assist mode As is performed in a torque rich region where the output is higher than that of the marine cubic characteristic line, it is also preferable from the viewpoint of environmental protection.

Further, since the engine 1 for ship propulsion is operated on a ship's cubic characteristic line in a steady state, the transition to the assist mode As is performed only when necessary, and immediately when the assist mode As is not necessary. To the gas mode G. Therefore, the engine 1 and the operation method thereof according to the present embodiment can be more suitably used in a tugboat with a large output fluctuation and an engine for a work boat.
In the present embodiment, in the gas mode G and the diesel mode D, variable intake valve timing mechanism in the case of changing the operation parameter for which control is performed in the operation of the engine 1, for example, the set value related to the air supply pressure and the valve closing timing The set values of the 30 controls (VIVT command value) and the set values related to the ignition conditions are set as the set values optimized for the respective operation modes. On the other hand, in the assist mode As, these operating parameters, that is, the set value for the air supply pressure, the set value of the control (VIVT command value) of the variable intake valve timing mechanism 30 when changing the valve closing timing of the intake valve, micro pilot injection The setting value common to the gas mode G is used for at least one of the setting values of the ignition device such as the valve 11 and the spark plug.

As described above, according to the dual fuel engine 1 and the operation method thereof according to this embodiment, the transition from the gas mode G to the assist mode As is, for example, 1 second, and the return from the assist mode As to the gas mode G is several seconds. Transition control can be done quickly in time. Therefore, occurrence of knocking and misfire in the gas mode G can be avoided in advance. The operation in the assist mode As is limited to a torque rich area where the output (load) is greatly increased, and when the need for the assist mode As using liquid fuel is eliminated, the gas mode G is promptly returned. Excellent effects can be obtained from the aspect of

The engine according to the present invention is not limited to the dual fuel engine 1 according to the above-described embodiment and its operating method, and appropriate changes, replacements, and the like can be made without departing from the scope of the present invention. Hereinafter, although the modification etc. of this invention are demonstrated, about the same or similar thing as the components, members, etc. which were demonstrated by embodiment mentioned above, description is abbreviate | omitted using the same code | symbol.

According to the present invention, the first operation in which the gaseous fuel is the major part of the heat source and the second operation in which both the gaseous fuel and the liquid fuel are fueled when the output (load) increases during the operation Abstract: An engine operation method and an engine system are provided which can shift between two driving states in accordance with a change in output (load) and rapidly.

DESCRIPTION OF SYMBOLS 1 dual fuel engine 2 crankshaft 8 intake valve 9 exhaust valve 10 fuel injection valve 11 micro pilot oil injection valve 12 fuel injection pump 13 intake pipe 14 exhaust pipe 15 fuel gas supply valve 20 rotational speed sensor 21 torque sensor 22 control unit 24 First map 25 Second map 30 Variable intake valve timing mechanism 44 Gas governor 45 Fuel gas supply valve timing mechanism 48 Diesel governor

Claims

The method of operating a dual fuel engine,
During the first operation in which the gas fuel is the major part of the heat source, the control of the supply amount of the gas fuel is terminated to reduce the supply amount of the gas fuel to a predetermined value and the adjustment of the supply amount of liquid fuel Transition to a second operation in which both the gaseous fuel and the liquid fuel are used as the control is started;
During the operation of the second operation, the regulation control of the supply amount of the liquid fuel is ended to reduce the supply amount of the liquid fuel and the regulation control of the supply amount of the gaseous fuel is started. Step of returning to one operation,
A method of operating an engine comprising:
The engine operating method according to claim 1, wherein the step of returning to the first operation is performed in the process of decreasing the output of the engine.
In the step of returning to the first operation, the step of reducing the liquid fuel supply amount includes a first step of reducing the liquid fuel supply amount at a relatively high speed, and a second step of reducing the liquid fuel supply amount at a relatively low speed. The method of operating an engine according to claim 1 or 2, further comprising: a stage.
The step of returning to the first operation is performed when the output of the engine enters the lower region of the assist off-line set in a range of ± 10% with respect to the marine cubic characteristic line,
The step of shifting to the second operation is performed when the output of the engine enters the upper region of the assist online set above the assist offline.
The operating method of an engine according to any one of claims 1 to 3.
The engine operating method according to any one of claims 1 to 4, wherein the supply amount of the gaseous fuel in the step of shifting to the second operation is a larger value as the output of the engine is larger.
The method of operating a dual fuel engine,
Performing a second operation using both gaseous fuel and liquid fuel subjected to temperature control as fuel;
Performing a first operation of terminating the control of the liquid fuel in the step and continuously reducing the supply amount of the liquid fuel and using the gaseous fuel as the major part of the heat source and performing the speed control;
A method of operating an engine comprising:
The method of operating a dual fuel engine,
A gas mode in which gaseous fuel is used as a major part of a heat source to control and control the gaseous fuel;
An assist mode for controlling and controlling the liquid fuel using both the gaseous fuel and the liquid fuel as fuel;
The engine is operated by selectively switching one of the liquid fuel as a fuel and the diesel mode in which the speed control is performed.
When the output of the engine enters an assist-off region set along a marine cubic characteristic line during operation in the assist mode, the gas mode is entered,
Transition to the assist mode when the output of the engine enters an assist on region where the output is higher than the assist off region during the operation in the gas mode
A method of operating an engine characterized by:
The engine operating method according to claim 7, wherein in the operation in the assist mode, an operation parameter to be controlled in the operation of the engine is the same setting as the gas mode.
It is a dual fuel engine system,
An operation control unit that performs operation control of the engine;
A gas governor that regulates the supply of gaseous fuel;
A control unit having a diesel governor for controlling the supply amount of liquid fuel;
During the first operation of using the gaseous fuel as the major part of the heat source by the operation control unit, the control of the gaseous fuel by the gas governor is terminated to reduce the supply amount of the gaseous fuel and the liquid by the diesel governor By starting the speed control of the fuel, it shifts to a second operation using both the gaseous fuel and the liquid fuel as fuel,
During the second operation, the control control of the liquid fuel by the diesel governor is ended to reduce the supply amount of the liquid fuel, and the control control of the gaseous fuel by the gas governor is started. An engine system characterized by returning to the operation of