WO2015129547A1

WO2015129547A1 - Dual-fuel engine, ship provided with same, and method for controlling dual-fuel engine

Info

Publication number: WO2015129547A1
Application number: PCT/JP2015/054659
Authority: WO
Inventors: 壮太渡邉; 平岡　直大; 耕之駒田; 石田　裕幸
Original assignee: 三菱重工業株式会社
Priority date: 2014-02-28
Filing date: 2015-02-19
Publication date: 2015-09-03
Also published as: CN106030076B; KR20160085899A; JP6297363B2; KR101854056B1; CN106030076A; JP2015165106A

Abstract

A dual-fuel engine capable of minimizing the supply of excessive amounts of heat when fuel is switched, and a method for controlling a dual-fuel engine. A dual-fuel engine (1) provided with a diesel mode in which the dual-fuel engine (1) is driven by petroleum alone and a gas mode in which the dual-fuel engine (1) is driven by petroleum and gas, and also provided with a control unit for switching between diesel mode and gas mode and controlling the amounts of both petroleum and gas injected into a cylinder, wherein when the control unit switches from diesel mode to gas mode, the control unit increases the amount of gas injected to a first prescribed amount in the case of a switch start command, and simultaneously reduces the amount of petroleum injected to an equivalent of the amount of heat in the first prescribed amount of gas, after which the control unit performs a control so as to gradually increase the amount of gas injected and gradually reduce the amount of petroleum injected.

Description

Dual fuel engine, ship equipped with the same, and control method of dual fuel engine

The present invention relates to a dual fuel engine, a ship equipped with the dual fuel engine, and a control method of the dual fuel engine.

Conventionally, diesel engines using petroleum as fuel have been used as internal combustion engines. However, in consideration of the environment, a dual fuel engine using gas and oil as fuel and switching between them is being studied.
For example, Patent Document 1 discloses that a fuel is switched and used in a dual fuel engine using gas and oil as fuel. When only oil is used as fuel, deposits are generated in the combustion chamber, which can interfere with the combustion process when gas is used as fuel. It is said that the deposit will be burned out by using 50% gas and 50% oil.
In addition, when gas is used as the main fuel, it is disclosed that oil is pilot-injected and ignited.

JP 2010-14112 A

However, in the invention disclosed in Patent Document 1, when the control of the injection valve for injecting gas is performed by, for example, an electromagnetic valve, the minimum fuel injection amount is finely controlled by the restriction on the minimum value of the minimum injection period of the electromagnetic valve. There is a problem that a considerable amount of gas is injected immediately after switching from oil to gas and the amount of heat temporarily supplied into the cylinder becomes excessive.

FIG. 3 shows a graph showing the elapsed time of the rotational speed of the dual fuel engine and the maximum in-cylinder pressure when the gas is excessively supplied as described above. In the figure, the horizontal axis represents time, and the vertical axis represents the rotational speed and maximum in-cylinder pressure of the dual fuel engine. Here, the maximum in-cylinder pressure is the maximum value of the in-cylinder pressure in a certain operating state, and is an allowable pressure (a value of the in-cylinder maximum pressure) that is unique to each engine determined in the design stage regardless of the operating state. Different from the upper limit).
When switching from a diesel mode in which only oil is the main fuel at time t = 0 to a gas mode in which the gas is the main fuel and the oil is the pilot fuel, when the gas is temporarily supplied excessively, As shown in FIG. 3, the in-cylinder maximum pressure of the dual fuel engine shows a suddenly high value from the previously stable value, and this state is continued for a while and then gradually decreases and becomes stable again. When the in-cylinder maximum pressure increases, the amount of work increases, so the rotational speed of the dual fuel engine also increases from a stable state to a high speed. Further, when the rotational speed of the dual fuel engine increases, an instruction to lower the fuel amount is issued, so that an increase in the gas injection amount is suppressed and the oil injection amount is greatly reduced.
In this way, when the fuel is switched, the gas is temporarily excessively supplied, so that fluctuations in the in-cylinder pressure, the rotational speed, and the total heat amount (injection amount of each fuel) of the dual fuel engine increase. Unable to operate with stable combustion.

The present invention has been made in view of such circumstances, and is a dual fuel engine capable of suppressing supply of an excessive amount of heat at the time of fuel switching, a ship equipped with the same, and a control of the dual fuel engine It aims to provide a method.

In order to solve the above-described problems, the dual fuel engine of the present invention, a ship equipped with the dual fuel engine, and the control method of the dual fuel engine employ the following means.
The first aspect of the present invention switches between a first operation mode operated only by petroleum fuel and a second operation mode operated by the petroleum fuel and fuel gas, and the petroleum fuel and fuel gas. In the dual fuel engine having a control unit for controlling the injection amount of the fuel gas, the control unit increases the fuel gas injection amount by a predetermined amount when switching from the first operation mode to the second operation mode. At the same time, after the fuel gas injection amount corresponding to the predetermined amount of heat of the fuel gas is decreased, the fuel gas injection amount is gradually increased and the petroleum fuel injection amount is gradually decreased. It is a dual fuel engine that performs control as described above.

According to the first aspect, the dual fuel engine includes a first operation mode that is operated only by petroleum fuel, and a second operation mode that is operated by petroleum fuel and fuel gas. When switching from the first operation mode to the second operation mode, the fuel gas injection amount is increased by a predetermined amount so that the total heat amount does not change, and at the same time, the petroleum fuel injection amount corresponding to the predetermined heat amount of the fuel gas is increased. Then, the fuel gas injection amount is gradually increased and the fuel fuel injection amount is controlled to gradually decrease.
If the fuel gas injection valve is limited to the minimum value of the minimum injection period, such as an electromagnetic valve, and it is difficult to finely control the minimum fuel injection amount, the fuel gas is injected at the same time as switching. Immediately after the injection amount of the fuel gas is temporarily increased, an excessive amount of heat is supplied into the cylinder beyond the control command value. Therefore, in the first aspect, the fuel gas injection amount is increased by a predetermined amount so that the total amount of heat in the cylinder does not change when switching from the first operation mode to the second operation mode. By reducing the amount of petroleum fuel injection corresponding to a certain amount of heat, fluctuations in the amount of heat supplied into the cylinder can be suppressed. As a result, it is possible to perform stable switching control while suppressing fluctuations in the in-cylinder pressure of the dual fuel engine, and to minimize fluctuations in NOx and fuel consumption as much as possible.

In the above aspect, the control unit gradually decreases the injection amount of the petroleum fuel to the pilot injection amount and gradually increases the fuel gas to an injection amount corresponding to a heat amount obtained by removing the heat amount of the pilot injection amount from the total heat amount. It is good also as a structure which increases to.

According to the above configuration, the fuel fuel injection amount is gradually decreased to the pilot injection amount, and the fuel gas is gradually increased to the injection amount corresponding to the heat amount obtained by removing the heat amount of the pilot injection amount from the total heat amount. Petroleum fuel can be used as the pilot fuel necessary for the combustion of the fuel gas, and since the total heat quantity does not change, fluctuations in the quantity of heat supplied into the cylinder can be suppressed. As a result, it is possible to perform stable switching control while suppressing fluctuations in the in-cylinder pressure of the dual fuel engine, and to minimize fluctuations in NOx and fuel consumption as much as possible.

The second aspect of the present invention switches between a first operation mode operated by only petroleum fuel and a second operation mode operated by the petroleum fuel and fuel gas, and the petroleum fuel and fuel gas. In the dual fuel engine having a control unit for controlling the injection amount of the fuel gas, the control unit gradually decreases the fuel gas injection amount when switching from the second operation mode to the first operation mode. The fuel fuel injection amount is gradually increased and then the fuel gas injection amount is decreased by a predetermined amount upon completion of switching, and at the same time, the petroleum fuel injection amount corresponding to a predetermined amount of heat of the fuel gas is reduced. It is a dual fuel engine that performs control so as to increase.

According to the second aspect, when switching from the second operation mode to the first operation mode, the ratio of the fuel gas injection amount is gradually decreased and the ratio of the petroleum fuel injection amount is gradually increased. Control is performed such that the fuel gas injection amount is decreased by a predetermined amount so that the total heat amount does not change when the switching is completed, and at the same time, the fuel fuel injection amount corresponding to the predetermined amount of heat of the fuel gas is increased.
When the fuel gas injection valve has a restriction on the minimum value of the minimum injection period, such as an electromagnetic valve, and it is difficult to finely control the minimum fuel injection amount, the fuel gas injection is gradually reduced at the time of switching. When the switching is completed, the fuel gas injection amount is temporarily greatly reduced, and the amount of heat supplied into the cylinder is greatly reduced from the control command value.
Therefore, in the second aspect, the fuel gas injection amount is decreased by a predetermined amount so that the total heat amount in the cylinder does not change when the switching from the second operation mode to the first operation mode is completed, and at the same time, By increasing the injection amount of petroleum fuel corresponding to a predetermined amount of heat, fluctuations in the amount of heat supplied into the cylinder can be suppressed. As a result, it is possible to perform stable switching control while suppressing fluctuations in the in-cylinder pressure of the dual fuel engine, and to minimize fluctuations in NOx and fuel consumption as much as possible.

In any one of the above aspects, the predetermined amount of the fuel gas may be greater than or equal to a minimum injection amount of the minimum injection period of the fuel gas injection valve.

According to the above configuration, since the predetermined amount of the fuel gas is equal to or greater than the minimum injection amount of the minimum injection period of the fuel gas injection valve, a controllable value can be set and the specification of the fuel gas injection valve is limited. In order to prevent the heat amount of the fuel gas from fluctuating when switching between the first operation mode and the second operation mode, the fluctuation of the amount of heat supplied into the cylinder is suppressed so that the total heat quantity in the cylinder does not change. Can do.

In any one of the above aspects, the control unit includes a supply pressure of the fuel gas, the predetermined amount of the fuel gas corresponding thereto, and an injection amount of the petroleum fuel corresponding to the predetermined amount of heat of the fuel gas. A table for storing in association with each other, detecting the supply pressure of the fuel gas at the start of switching between the first operation mode and the second operation mode, and based on the detected supply pressure, the fuel from the table The predetermined amount of gas and the corresponding fuel fuel injection amount may be acquired.

According to the above configuration, the supply pressure of the fuel gas, the predetermined amount of the fuel gas injection amount corresponding thereto, and the fuel fuel injection amount corresponding to the heat amount are stored in the table in advance in association with each other, and the detected supply By supplying a predetermined amount and an injection amount corresponding to the pressure, the fuel gas injection heat amount varies depending on the supply pressure, but an appropriate amount of fuel gas injection amount and petroleum fuel injection amount can be determined, The total amount of heat in the cylinder does not change, and stable switching control can be performed while suppressing fluctuations in the cylinder pressure.

A third aspect of the present invention is a ship including the dual fuel engine according to any one of the above and a hull on which the dual fuel engine is mounted.

According to the third aspect, since any one of the dual fuel engines described above is mounted on a ship, stable switching control can be performed while suppressing fluctuations in the in-cylinder pressure of the engine. As a result, it is possible to operate the ship in consideration of the environment while minimizing fluctuations in NOx and fuel consumption as much as possible.

According to a fourth aspect of the present invention, there is provided a control method for a dual fuel engine comprising: a first operation mode that is operated only by petroleum fuel; and a second operation mode that is operated by the petroleum fuel and fuel gas. When switching from the first operation mode to the second operation mode, the fuel gas injection amount is increased by a predetermined amount, and at the same time, the petroleum fuel injection amount corresponding to a predetermined amount of heat of the fuel gas is decreased. And a step of gradually increasing the injection amount of the fuel gas and gradually decreasing the injection amount of the petroleum fuel.

According to the fourth aspect, the dual fuel engine includes a first operation mode that is operated only by petroleum fuel, and a second operation mode that is operated by petroleum fuel and fuel gas. When switching from the first operation mode to the second operation mode, the fuel gas injection amount is increased by a predetermined amount so that the total heat amount does not change, and at the same time, the petroleum fuel injection amount corresponding to the predetermined heat amount of the fuel gas is increased. Then, the fuel gas injection amount is gradually increased and the fuel fuel injection amount is controlled to gradually decrease.
If the fuel gas injection valve is limited to the minimum value of the minimum injection period, such as an electromagnetic valve, and it is difficult to finely control the minimum fuel injection amount, the fuel gas is injected at the same time as switching. Immediately after the injection amount of the fuel gas is temporarily increased, an excessive amount of heat is supplied into the cylinder beyond the control command value. Therefore, in the fourth aspect, the fuel gas injection amount is increased by a predetermined amount so that the total heat amount in the cylinder does not change at the time of switching, and at the same time the petroleum fuel injection amount corresponding to the predetermined amount of heat of the fuel gas is decreased. By doing so, the fluctuation | variation of the calorie | heat amount supplied in a cylinder can be suppressed. As a result, it is possible to perform stable switching control while suppressing fluctuations in the in-cylinder pressure of the dual fuel engine, and to minimize fluctuations in NOx and fuel consumption as much as possible.

According to the present invention, it is possible to suppress fluctuations in the supply of heat quantity of the fuel gas, so it is possible to suppress supply of excessive heat quantity into the cylinder, and to reduce fluctuations in the in-cylinder pressure and rotation speed of the dual fuel engine. Suppressing and stable switching control can be performed.

It is the cross-sectional view and longitudinal cross-sectional view which showed the process of each fuel injection of the dual fuel engine which concerns on 1st Embodiment of this invention. It is the graph which showed the time passage of the calorie | heat amount of the petroleum fuel and fuel gas of the dual fuel engine which concerns on 1st Embodiment of this invention. It is the graph which showed the time passage of the rotation speed of the dual fuel engine concerning a 1st embodiment of the present invention, and the maximum in-cylinder pressure. It is the graph which showed the fuel gas injection valve injection period and fuel gas injection valve injection quantity of the fuel gas which concern on 2nd Embodiment of this invention.

Hereinafter, an embodiment of a dual fuel engine according to the present invention, a ship equipped with the dual fuel engine, and a control method of the dual fuel engine will be described with reference to the drawings.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a schematic configuration and a process of injecting each fuel of a dual fuel engine, a ship equipped with the dual fuel engine, and a control method of the dual fuel engine according to the present embodiment.
As shown in FIG. 1, the dual fuel engine 1 includes a cylinder portion 10, a piston 20, a fuel gas injection valve 101, and a fuel injection valve 103 as main components.
The dual fuel engine 1 is provided with a cylinder portion 10 including a cylinder liner (not shown), a cylinder cover (not shown), and the like, and a piston 20 is disposed inside the cylinder portion 10. Power is taken out by a connecting rod, a crankshaft, etc. (not shown) connected to the piston 20.
Each fuel is injected and supplied to the dual fuel engine 1 from the fuel gas injection valve 101 and the fuel injection valve 103, and the fuel is combusted inside the cylinder portion 10.
The dual fuel engine 1 is mounted on a ship, for example, and the power extracted outside is transmitted to a propeller and output as a propulsion force of the ship.

The fuel gas injection valve 101 is controlled by an electromagnetic valve, and a gas (fuel gas) whose pressure is increased to, for example, about 150 to 250 bar according to a period during which the electromagnetic valve is opened is injected into the cylinder. The fuel injection valve 103 is, for example, a fuel injection valve used in a low-speed two-stroke cycle diesel engine, and oil (petroleum fuel) boosted by a fuel injection pump according to the opening of the fuel injection valve is in the cylinder. Be injected. The fuel gas injection valve 101 and the fuel injection valve 103 are controlled by a control unit (not shown). Further, each fuel gas injection valve 101 and each fuel injection valve 103 are disposed at positions that are symmetric about the central axis of the cylinder portion 10 above the cylinder portion 10.
Here, as the gas, any of compressed natural gas (CNG), liquefied propane gas (LPG), or the like obtained by gasifying and increasing the pressure of liquefied natural gas (LNG) may be used. Moreover, any oil such as heavy oil or light oil may be used.

The dual fuel engine 1 is switched by the control unit between a diesel mode (first operation mode) using only oil as a main fuel and a gas mode (second operation mode) using gas as a main fuel, Driving is performed according to the mode. When operating in the gas mode, pilot ignition fuel for pilot ignition is required. In this embodiment, oil is used as the pilot injection fuel. Moreover, below, let the period which switches diesel mode and gas mode be a switching period.

FIGS. 1A to 1C show the process of fuel injection in the gas mode in which gas is the main fuel and oil is the pilot fuel.
FIG. 1A shows the compression stroke, fuel is not injected from the fuel gas injection valve 101 and the fuel injection valve 103, and only air is supplied above the piston 20 inside the cylinder portion 10. As the piston 20 moves upward, the air inside the cylinder portion 10 is compressed.
FIG. 1B of the next stroke shows the ignition stroke, and the piston 20 has moved to the vicinity of the top dead center. At this time, pilot oil necessary for gas ignition is injected from the fuel injection valve 103, and gas is injected from the fuel gas injection valve 101. At this time, the fuel injection valve 103 is used as a pilot valve for igniting the gas.
FIG. 1C of the next stroke shows the combustion / expansion stroke, and the gas and pilot oil injected in FIG. The burned gas expands and pushes the piston 20 back downward.
By repeating these strokes, the piston 20 moves up and down, and power is taken out by a connected crankshaft (not shown) or the like.

FIG. 2 shows a graph showing the passage of time between the amount of heat of oil injected from the fuel injection valve 103 into the cylinder and the amount of heat of gas injected from the fuel gas injection valve 101 into the cylinder.
In FIG. 2, the horizontal axis is time, and the vertical axis is a coefficient corresponding to the amount of heat of oil and gas. For the coefficient on the vertical axis, the desired value of the total in-cylinder heat in the operation before and after fuel switching is set to 1. In addition, the thick line and the thick broken line are a control value (a ratio of the control heat quantity to the total heat quantity) and a conventional control value (a control value of the conventional example, a ratio of the conventional control heat quantity to the total heat quantity) controlled by the gas control unit, The thin line and the thin broken line are the control value of petroleum and the conventional control value.
In FIG. 2, the control values of oil and gas and the conventional control values of oil and gas when switching to the gas mode after switching from the operation in the diesel mode are shown over time. Here, the time t at the start of the switching period is set to zero.

When switching from the diesel mode to the gas mode, the control unit controls the fuel gas injection valve 101 to open, but since the supplied gas is a high-pressure gas, the control of the fuel gas injection valve 101 is performed by an electromagnetic valve. It is known that there is a restriction on the minimum value of the minimum injection period (for example, 3 to 4 ms). Therefore, since the fuel gas injection valve 101 cannot perform fine control below the minimum injection period and cannot gradually increase the injection amount according to the control command value, the minimum injection amount larger than the control command value is injected. Will do.
On the other hand, since the amount of oil injected from the fuel injection valve 103 is gradually reduced, the amount of increase in the amount of injected gas exceeds the amount of decrease in the amount of injected oil, and the cylinder 10 Is supplied with an amount of heat that is more than the desired total amount of heat.

Therefore, as shown in the graph of gas and oil control values in FIG. 2, when switching from the diesel mode to the gas mode, the control unit sets the first predetermined amount (heat amount) to the fuel gas injection valve 101 at the time of switching. An instruction to increase (corresponding to Fs) and an instruction to decrease the injection amount corresponding to the first predetermined amount of heat Fs of gas to the fuel injection valve 103 at the same time. Here, it is assumed that the first predetermined amount is an injection amount equal to or greater than the minimum injection amount of the minimum injection period of the fuel gas injection valve 101. By this instruction, at time t = 0 in FIG. 2, the gas injection amount suddenly rises discontinuously from 0 to the first predetermined amount. Also, at time t = 0 in FIG. 2, the oil rapidly decreases discontinuously from the injection amount corresponding to the total heat amount by the injection amount corresponding to the first predetermined amount of heat Fs of the gas.
After injecting the first predetermined amount of gas and injecting the amount of oil corresponding to the heat quantity (1-Fs) obtained by removing the first predetermined amount of heat Fs from the total heat quantity, the control unit An instruction to continuously and gradually decrease the injection amount so as to become F1 corresponding to the pilot injection amount at t2, and a heat amount F2 obtained by subtracting the heat amount corresponding to the pilot injection amount from the total heat amount at time t2 = An instruction is given to gradually and gradually increase the injection amount so as to be 1-F1. An instruction to decrease the injection amount of oil and an instruction to increase the injection amount of gas are directed to decrease and increase in a linear function, respectively, so as to suppress fluctuations in the total heat amount. However, the tendency of the decrease and increase is not limited to the example shown in FIG. 2, and if the control is to suppress the fluctuation of the total heat amount, for example, the decrease instruction and the increase instruction that are changed in a curve shape in a quadratic function. There may be.

At time t2, the heat quantity of gas is F2, and the heat quantity of oil is F1, and after time t2, the dual fuel engine 1 is operated in the gas mode. Here, t2 may be the same value as t3, or a value that can be set as appropriate.
By controlling as described above, fluctuations in the total amount of heat supplied into the cylinder can be suppressed even during the switching period between time t = 0 and t2.

Further, when switching from the gas mode to the diesel mode, it is difficult to finely control the minimum injection amount due to the restriction on the minimum value of the minimum injection period of the fuel gas injection valve 101, and gradually according to the control command value. Therefore, when the switching is completed, the gas injection amount is temporarily greatly reduced, and the total amount of heat supplied into the cylinder is greatly reduced from the control command value.
Therefore, the control unit first gives an instruction to gradually increase the injection amount so that the amount of heat of petroleum becomes the total amount of heat, and an instruction to gradually decrease the injection amount so that the amount of heat of gas becomes zero. When the switching is completed, the fuel gas injection valve 101 is instructed to decrease the second predetermined amount, and the fuel injection valve 103 is instructed to increase the injection amount corresponding to the second predetermined amount of heat. Here, the second predetermined amount is assumed to be an injection amount equal to or greater than the minimum injection amount of the minimum injection period of the fuel gas injection valve 101. By this instruction, when the switching is completed, the oil injection amount suddenly rises discontinuously from the pilot injection amount by the injection amount corresponding to the second predetermined amount of heat, and at the same time, the gas is inactivated by the second predetermined amount. It decreases rapidly continuously.

As described above, according to the dual fuel engine, the ship including the dual fuel engine, and the control method of the dual fuel engine according to the present embodiment, the following operational effects can be obtained.
The dual fuel engine 1 includes a diesel mode that is operated only by oil and a gas mode that is operated by oil and gas. When changing from the diesel mode to the gas mode, the gas injection amount is increased by a first predetermined amount so that the total heat amount in the cylinder does not change, and at the same time, the oil injection amount corresponding to the first predetermined amount of heat of the gas is decreased. Thereafter, control is performed such that the gas injection amount is gradually increased and the oil injection amount is gradually decreased.
If the fuel gas injection valve 101 has a restriction on the minimum value of the minimum injection period and it is difficult to finely control the minimum injection amount, the gas and oil injection amounts in FIG. If the control to switch is performed and gas is injected at the same time as the switch start command, fine control below the minimum injection period cannot be performed, and the gas injection amount immediately after the switch start becomes temporarily larger than the control command value for the gas A large amount of heat is supplied into the cylinder. At this time, since the oil injection amount is gradually decreased according to the control command value, the increase amount of the gas injection amount exceeds the decrease amount of the oil injection amount, and the cylinder portion 10 has a desired amount in the cylinder. An excessive amount of heat is supplied than the total amount of heat. When the amount of heat exceeding the desired total amount of heat is supplied into the cylinder, as shown in FIG. 3, the maximum pressure in the cylinder of the dual fuel engine shows a suddenly high value from the previously stable value. That state continues for a while. When the in-cylinder maximum pressure increases, the amount of work increases, so the rotational speed of the dual fuel engine also increases from a stable state to a high speed. Further, when the rotational speed of the dual fuel engine increases, an instruction to lower the fuel amount is issued, so that an increase in the gas injection amount is suppressed and the oil injection amount is greatly reduced.
As described above, when the gas is temporarily excessively supplied, fluctuations in the in-cylinder pressure, the rotational speed, and the total heat amount (injection amount of each fuel) of the dual fuel engine become large, and stable combustion results. I can't drive.
According to the present embodiment, the gas injection amount is increased by the first predetermined amount so that the total heat amount in the cylinder does not change when switching from the diesel mode to the gas mode, and at the same time, it corresponds to the first predetermined amount of heat of the gas. By reducing the amount of oil injected, fluctuations in the amount of heat supplied into the cylinder can be suppressed. Thus, stable switching control can be performed while suppressing fluctuations in the in-cylinder pressure and rotation speed of the dual fuel engine 1, and fluctuations in NOx and fuel consumption can be minimized as much as possible.

In addition, the oil injection amount is gradually reduced to the pilot injection amount, and the gas is gradually increased to the injection amount corresponding to the heat amount obtained by excluding the heat amount of the pilot injection amount from the total heat amount. Petroleum can be used as the pilot fuel, and since the total amount of heat does not change, fluctuations in the amount of heat supplied into the cylinder can be suppressed. As a result, it is possible to perform stable switching control while suppressing fluctuations in the in-cylinder pressure of the dual fuel engine 1, and to minimize fluctuations in NOx and fuel consumption as much as possible.

In addition, when the switching from the gas mode to the diesel mode is completed, the gas injection amount is decreased by a second predetermined amount so that the total heat amount in the cylinder does not change, and at the same time, the oil injection amount corresponding to the second predetermined amount of heat of the gas By increasing the value, fluctuation in the amount of heat supplied into the cylinder in switching from the gas mode to the diesel mode can be suppressed. As a result, it is possible to perform stable switching control while suppressing fluctuations in the in-cylinder pressure of the dual fuel engine 1, and to minimize fluctuations in NOx and fuel consumption as much as possible.

Further, since the first predetermined amount and the second predetermined amount of gas are equal to or greater than the minimum injection amount of the minimum injection period of the fuel gas injection valve 101, a controllable value equal to or greater than the minimum injection amount is set in advance. In order to suppress fluctuations in the amount of heat of the gas when switching between the diesel mode and the gas mode due to the restriction of the specifications of the fuel gas injection valve 101 by offsetting the amount of heat by setting the amount of oil injection of the corresponding amount of heat, Variation in the amount of heat supplied to the cylinder can be suppressed so that the total amount of heat in the cylinder does not change.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment described above, the injection amount of each fuel to be increased or decreased at the time of switching of each fuel is determined as one value, but in this embodiment, the injection amount of each fuel is set according to the gas pressure. is there. Since the other points are the same as in the first embodiment, the same components are denoted by the same reference numerals and the description thereof is omitted.

FIG. 4 shows a graph showing the fuel gas injection valve injection period and the fuel gas injection valve injection amount according to the present embodiment. In the figure, the horizontal axis represents the injection period of the fuel gas injection valve 101, and the vertical axis represents the injection amount of the fuel gas injection valve 101 for each cycle. tn indicates the minimum injection period, which is the lower limit of the injection period determined by the solenoid valve.
As shown in FIG. 4, as the injection period becomes longer, the injection amount also increases. Further, when the gas pressure is increased to, for example, 20 MPa, 25 MPa, and 30 MPa, not only the minimum injection amount in the minimum injection period tn but also the injection amount in the same injection period increases. The minimum injection period tn is determined by the electromagnetic valve used for the fuel gas injection valve 101, and therefore shows the same value regardless of the gas pressure.
As described above, since the minimum injection amount in the minimum injection period tn changes according to the gas pressure, in the present embodiment, the gas supply pressure, the first predetermined amount of gas and the first predetermined amount of gas corresponding thereto are changed. The control unit is provided with a table that stores the oil injection amount corresponding to the heat amount in association with each other.
The gas supply pressure and the first predetermined amount of gas corresponding thereto are expressed by the following equation (1).
[Equation 1]
Q'∝ Hu ¹ × ρ _f ^1/2 × ΔP ^1/2 × do ² (1)

(1) In the equation, Q'is input gas heating value per unit time [kJ / s], Hu is the lower heating value of gas [kJ / kg], ρ _f is the nozzle hole of the fuel gas injector 101 The gas density [kg / m ³ ] at the outlet, ΔP is the effective injection pressure [Pa] of the fuel gas injection valve 101, and do is the nozzle diameter [m] of the fuel gas injection valve 101.
ΔP is (injection pressure of the fuel gas injection valve 101) − (internal pressure of the cylinder part 10).
In the choke condition, [Delta] P is (injection pressure of the fuel gas injector 101) - (chalk pressure), [rho _f is the density at the choke.

The control unit refers to the table based on the gas pressure detected by a sensor (not shown) for detecting the gas pressure at the start of switching from the diesel mode to the gas mode, and the first location of the gas corresponding to the gas pressure from the table. The fixed quantity and the amount of oil injection corresponding to the first predetermined amount of heat of gas are acquired. The control unit corresponds to an instruction to increase the first predetermined amount of gas acquired from the table to the fuel gas injection valve 101 and a first predetermined amount of heat of the gas acquired from the table to the fuel injection valve 103. An instruction to reduce the amount of oil injection is given at the same time.

In addition, the control unit includes a table that stores the gas supply pressure in association with the second predetermined amount of gas and the amount of oil injection corresponding to the heat amount of the second predetermined amount of gas.
The control unit refers to the table based on the gas pressure detected by a sensor (not shown) that detects the gas pressure at the start of switching from the gas mode to the diesel mode, and the second location of the gas corresponding to the gas pressure from the table. The fixed amount and the amount of oil injection corresponding to the second predetermined amount of heat of gas are acquired. When the switching is completed, the control unit instructs the fuel gas injection valve 101 to decrease the second predetermined amount of gas acquired from the table, and instructs the fuel injection valve 103 to set the second predetermined amount of gas acquired from the table. An instruction to increase the amount of oil injection corresponding to the amount of heat is simultaneously given.

As described above, according to the dual fuel engine, the ship including the dual fuel engine, and the control method of the dual fuel engine according to the present embodiment, the following operational effects can be obtained.
The gas supply pressure, the first or second predetermined amount of gas injection corresponding thereto, and the oil injection amount corresponding to the heat amount are associated with each other in advance and stored in a table in accordance with the detected supply pressure. By acquiring the gas and oil injection amounts and supplying them into the cylinder of the cylinder unit 10, the gas injection heat amount varies depending on the supply pressure, but an appropriate amount of gas injection amount and oil injection amount are determined. Thus, the total amount of heat in the cylinder does not change, and stable switching control can be performed while suppressing fluctuations in the cylinder pressure.

As mentioned above, although each embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention. .

For example, in the above-described embodiment, the gas pressure, the first or second predetermined amount of gas corresponding to the gas pressure, and the oil injection amount corresponding to the heat amount are associated with each other and stored in the table. The amount of heat (corresponding to the injection amount) set and calculated in the above equation (1) may be set.

1 Dual Fuel Engine 10 Cylinder 20 Piston 101 Fuel Gas Injection Valve 103 Fuel Injection Valve

Claims

A control unit that switches between a first operation mode that is operated only by petroleum fuel and a second operation mode that is operated by the petroleum fuel and fuel gas, and that controls an injection amount of the petroleum fuel and the fuel gas. In the dual fuel engine provided,
The control unit increases the fuel gas injection amount by a predetermined amount when switching from the first operation mode to the second operation mode, and at the same time, the petroleum fuel corresponding to the predetermined amount of heat of the fuel gas. After reducing the injection amount of
A dual fuel engine that performs control so as to gradually increase the fuel gas injection amount and gradually decrease the petroleum fuel injection amount.
The control unit gradually decreases the injection amount of the petroleum fuel to a pilot injection amount, and gradually increases the fuel gas to an injection amount corresponding to a heat amount obtained by subtracting the heat amount of the pilot injection amount from the total heat amount. Item 2. The dual fuel engine according to Item 1.
A control unit that switches between a first operation mode that is operated only by petroleum fuel and a second operation mode that is operated by the petroleum fuel and fuel gas, and that controls an injection amount of the petroleum fuel and the fuel gas. In the dual fuel engine provided,
The control unit gradually decreases the fuel gas injection amount when switching from the second operation mode to the first operation mode and gradually increases the petroleum fuel injection amount, and then completes the switching. A dual fuel engine that performs control so as to reduce the fuel gas injection amount by a predetermined amount and at the same time increase the petroleum fuel injection amount corresponding to a predetermined amount of heat of the fuel gas.
The dual fuel engine according to any one of claims 1 to 3, wherein the predetermined amount of the fuel gas is equal to or greater than a minimum injection amount of the minimum injection period of the fuel gas injection valve.
The control unit includes a table that associates and stores the supply pressure of the fuel gas, the predetermined amount of the fuel gas corresponding thereto, and an injection amount of the petroleum fuel corresponding to the predetermined amount of heat of the fuel gas. Detecting the supply pressure of the fuel gas at the start of switching between the first operation mode and the second operation mode, and based on the detected supply pressure, the predetermined amount of the fuel gas from the table and The dual fuel engine according to any one of claims 1 to 4, wherein a corresponding injection amount of the petroleum fuel is acquired.
A dual fuel engine according to any one of claims 1 to 5;
A ship equipped with a hull carrying the dual fuel engine.
In a control method for a dual fuel engine, comprising: a first operation mode operated only by petroleum fuel; and a second operation mode operated by the petroleum fuel and fuel gas.
When switching from the first operation mode to the second operation mode, the fuel gas injection amount is increased by a predetermined amount, and at the same time, the petroleum fuel injection amount corresponding to a predetermined amount of heat of the fuel gas is decreased. Steps,
And a step of gradually increasing the fuel gas injection amount and gradually decreasing the oil fuel injection amount.