KR20170102551A - Control device of internal-combustion engine, and ship provided with same, and method of operating internal-combustion engine - Google Patents

Abstract

In the internal combustion engine, emission of NOx can be suppressed without using an additional device in the exhaust-regulation-strengthened waters, and the output of the engine can be ensured in other sea areas.
A combustion mode selecting means (44) for selecting at least a fuel gas diffusion combustion mode and a fuel gas premix combustion mode during operation of the internal combustion engine, fuel injection control means for controlling fuel injection such that a fuel injection mode according to the selected combustion mode And the actual compression ratio changing means (48) changes the actual compression ratio according to the selected combustion mode. When the internal combustion engine is switched to the fuel gas premix combustion mode, the actual compression ratio changing means (48) The compression ratio is changed to a low compression ratio, and the actual compression ratio is changed to the high compression ratio ratio when the fuel gas diffusion combustion mode is switched to.

Description

TECHNICAL FIELD [0001] The present invention relates to a control apparatus for an internal combustion engine, a ship having the same, and a method of operating the internal combustion engine. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

The present invention relates to a control apparatus for an internal combustion engine that performs premixed combustion using fuel gas, a ship having the internal combustion engine, and a method of operating the internal combustion engine.

Recently, dual fuel engines (hereinafter also referred to as "DF engines") that can be applied to low-speed two-stroke diesel engines for marine engines have been developed (see Patent Documents 1 and 2 below). This DF engine is provided with a fuel oil operation for burning fuel oil and a fuel gas operation for burning fuel gas such as LNG as in the conventional operation mode. In the fuel gas operation, fuel oil is generally used as pilot fuel for ignition.

Further, in such a DF engine, a fuel oil diffusion combustion system that generally performs diffusive combustion of fuel oil is employed in the fuel oil operation, but in the fuel gas operation, the fuel gas diffusion combustion system , And a fuel gas premixed combustion method in which premixed combustion of fuel gas is performed.

Japanese Patent No. 5395848 International Publication No. 2013/183737 A1

However, according to the premixing method, EGR and SCR are unnecessary because the emission of harmful NOx is small. However, the premixing method tends to cause abnormal combustion such as overcharge ignition and knocking. To avoid this, the compression ratio must be lower than that of a normal diesel engine. Therefore, there is a problem that the maximum output is limited in the premixed system. When the fuel oil operation is performed with the DF engine having the lower compression ratio, the thermal efficiency is lowered due to the low compression ratio.

On the other hand, since the fuel gas diffusion combustion system and the fuel oil diffusion combustion system have no fear of abnormal combustion, the compression ratio can be made as high as that of a normal diesel engine, and there is no output limitation in this respect. However, when fuel oil operation is performed with a DF engine having a high compression ratio as described above, there is no reduction in thermal efficiency. However, since NOx emissions are increased, additional devices such as EGR and SCR There is a problem that needs to be done.

The present invention provides a control apparatus for an internal combustion engine capable of suppressing the emission of NOx without using an additional device in an exhaust-gas-enriched sea area and ensuring an output of the engine in other sea areas, And an operation method of the internal combustion engine.

(1) In order to achieve the above object, a control apparatus for an internal combustion engine according to the present invention comprises combustion mode selection means capable of selecting at least a fuel gas diffusion combustion mode and a fuel gas premixed combustion mode during operation of an internal combustion engine, Fuel injection control means for controlling the fuel injection so as to achieve the fuel injection mode according to the combustion mode selected by the selection means; and actual compression ratio control means for controlling the actual compression ratio according to the combustion mode selected by the combustion mode selection means Wherein the actual compression ratio control means controls the actual compression ratio to a low compression ratio when the fuel gas premix combustion mode is selected and controls the actual compression ratio to a high compression ratio ratio when the fuel gas diffusion combustion mode is selected .

(2) The fuel gas premix combustion system includes a fuel gas preblend combustion system in which fuel gas is combusted only by a fuel gas premix combustion system, a fuel gas preblend combustion system in which a part of the fuel gas is premixed, Wherein the combustion mode selection means includes at least a fuel gas diffusion combustion mode, a pre-mixed combustion mode of the fuel gas, and a pre-mixed combustion mode of the fuel gas portion during the operation of the internal combustion engine, Wherein the actual compression ratio control means controls the actual compression ratio to a low compression ratio when the fuel gas pre-mixed combustion method or the fuel gas partial premixed combustion method is selected, and the fuel gas diffusion combustion method It is preferable to control the actual compression ratio to a high compression ratio.

(3) The engine includes a valve device capable of changing an exhaust valve closure timing, and the actual compression ratio control means controls the actual compression ratio by operating the exhaust valve closure timing, It is preferable to control the timing of closing the exhaust valve to the retard angle side and control the timing of closing the exhaust valve to the advance angle side when the actual compression ratio is set to the high compression ratio.

(4) The engine is provided with a supercharger capable of increasing and decreasing the supercharging amount, and when the combustion mode selecting means selects the fuel gas diffusion combustion mode in the case of at least a high load state in which the load of the internal combustion engine is larger than a predetermined load And supercharging control means for bringing the supercharged amount into a normal state and making the supercharged amount increase state when the combustion mode selection means selects the fuel gas premixed combustion mode.

(5) In this case, the supercharger may be a supercharger capable of switching between a supercharger of two stages and a supercharger once, wherein the supercharger control means, when the supercharger is in a normal state, supercharges the supercharger once, State, it is preferable that the supercharger is a two-stage supercharger.

(6) When the combustion mode selection means selects the fuel gas diffusion combustion mode, the supercharging control means sets the supercharged amount to the increased state when the load of the internal combustion engine is a low load state below the predetermined load .

(7) a judging means for judging whether or not the exhaust gas is in a regulated state in which the exhaust of the engine is to be regulated, and the combustion mode selecting means, when it is judged by the judging means that the exhaust gas is regulated, It is preferable to select the combustion mode, and to select the fuel gas diffusion combustion mode if it is determined by the determination means that the exhaust gas is not regulated.

(8) The marine vessel engine as set forth in any one of (8) to (7) above, wherein the determination means determines that the marine vessel is in the exhaust- It is determined that the state is not the above exhaust regulation state.

(9) A ship of the present invention is characterized by having the internal combustion engine control apparatus described in any one of (1) to (8) and the internal combustion engine controlled by the control apparatus.

(10) A method of operating an internal combustion engine according to the present invention includes: a combustion mode selection step of selecting at least one of a combustion mode including a fuel gas diffusion combustion mode and a fuel gas premixed combustion mode during operation of an internal combustion engine; And a compression ratio control step of controlling the actual compression ratio of the internal combustion engine according to the selected combustion mode in the combustion mode selection step.

(11) The fuel gas pre-mixed combustion method is a fuel gas pre-mixed combustion method in which fuel gas is used to burn only in a fuel gas premix combustion manner, a fuel pre-mixture combustion method in which a part of the fuel gas is premixed, Gas mixture pre-mixed combustion system, wherein, during the operation of the internal combustion engine, at least the fuel gas diffusion combustion mode, the fuel gas pre-mixed combustion mode, the fuel gas partial premixing It is preferable to select one of the combustion methods including the combustion method.

According to the present invention, the fuel injection control means controls the fuel injection so as to be the fuel injection mode according to the selected combustion mode, and the actual compression ratio control means controls the actual compression ratio to be the actual compression ratio according to the selected combustion mode, The compression ratio control means controls the actual compression ratio to a low compression ratio when the fuel gas premix combustion method is selected and controls the actual compression ratio to a high compression ratio ratio when the fuel gas diffusion combustion method is selected. The method can be stably performed. Thus, for example, in a marine engine, it is possible to suppress the emission of NOx without using an additional device by selecting a fuel gas pre-mixed combustion method in the exhaust-regulation enhanced sea area, and in other sea areas, The output of the engine can be secured.

In addition, the fuel gas premix combustion method of the internal combustion engine includes a fuel gas preblend combustion method in which the fuel gas is combusted only by the fuel gas premix combustion method, a premix combustion method in which a part of the fuel gas is premixed and the remainder is diffused When the fuel gas partial premixed combustion mode is selected, the actual compression ratio control means controls the actual compression ratio to a low compression ratio when the fuel gas pre-mixture combustion mode or the fuel gas partial premixed combustion mode is selected, Is selected, the actual compression ratio is controlled to a high compression ratio, so that the fuel gas pre-mixed combustion method or the fuel gas partial premixed combustion method with a small NOx emission amount can be stably performed. Thus, for example, in a marine engine, it is possible to suppress the emission of NOx without using an additional device by selecting a fuel gas pre-mixed combustion method or a fuel gas partial premixed combustion method at the exhaust- In the outside sea area, the fuel gas diffusion combustion method can be selected to secure the output of the engine.

1 is a block diagram showing a control apparatus for an internal combustion engine according to a first embodiment of the present invention.
2 is an overall configuration diagram showing an internal combustion engine according to a first embodiment of the present invention.
Figs. 3A and 3B are schematic views of an in-cylinder circumferential configuration including the cylinder liner of Fig. 2, wherein Fig. 3A is a plan view and Fig. 3B is a longitudinal sectional view. 3A and 3B show a state in which the fuel gas is injected in the premixed fuel system.
4 is a time chart illustrating control by the control apparatus of the internal combustion engine according to the first embodiment of the present invention.
5 is a block diagram showing a control apparatus for an internal combustion engine according to a second embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

It should be noted that the embodiments described below are merely illustrative and are not intended to exclude the application of various modifications and techniques not described in the following embodiments. The respective constitutions of the following embodiments can be modified in various ways within a range not deviating from the purpose thereof, and can be selected as required or can be appropriately combined.

[First Embodiment]

[Configuration of Internal Combustion Engine]

A first embodiment of the present invention will be described. First, the structure of the internal combustion engine according to the present embodiment and a second embodiment to be described later will be described with reference to Figs. 2, 3A, and 3B.

As shown in Fig. 2, the internal combustion engine according to the embodiment of the present invention is a crosshead-type diesel engine (hereinafter simply referred to as an engine) 1 as well. The engine 1 is a low-speed two-stroke, one-cycle, sweeping system used as a ship cycle of a liquefied gas carrier such as an LNG carrier. Further, the engine 1 is configured as a dual-fuel engine (hereinafter also referred to as a DF engine) capable of using fuel gas in addition to fuel oil.

This engine 1 is provided with a base plate 3 located at the lower side, a furniture 5 formed on the base plate 3 and a jacket 7 formed on the furniture 5 . The base plate 3, the furniture 5 and the jacket 7 are integrally fastened and fixed by a plurality of tension bolts (not shown) extending in the vertical direction.

A cylinder liner 9 is formed on the jacket 7 and a plurality of scavenging ports 10 are formed on the lower end side of the cylinder liner 9. [ At the upper end of the cylinder liner 9, a cylinder cover 11 is formed. In the cylinder cover 11, an exhaust valve 12 is formed. As described above, air is introduced from the scavenging port 10 formed at the lower end side of the cylinder liner 9 into the cylinder from below in a scavenging manner, and the combustion exhaust gas is exhausted from the exhaust valve 12 located above the cylinder. A scavenging method is adopted.

The exhaust gas discharged from the exhaust valve 12 is collected in the exhaust gas manifold 14 and then sent to the supercharger 16. [ In the supercharger 16, the exhaust turbine (not shown in Fig. 2) is rotated by the guided exhaust gas, whereby the coaxially connected compressor (not shown in Fig. 2) is rotated. The compressor compresses the air from the outside, and is cooled in the air cooler 18 and then guided to the scavenging manifold 20. The compressed air introduced into the scavenging manifold 20 is introduced into the scavenging port 10 described above. Details of the turbocharger 16 will be described later.

A piston 13 is reciprocally movable in a space formed by the cylinder liner 9 and the cylinder cover 11. [ At the lower end of the piston 13, the upper end of the piston rod 15 is rotatably mounted. The diesel engine 1 of the present embodiment is an ultra long stroke having a bore stroke ratio of 3 or more, which is the ratio of the stroke of the piston 13 to the inner diameter of the cylinder liner 9. [

The base plate 3 is a crankcase, and a crankshaft 17 is formed. The rotary output taken out from the crankshaft 17 is transmitted to the propulsion propeller of the ship. A lower end of the connecting rod 19 is rotatably connected to the upper end of the crankshaft 17.

The furniture 5 is provided with a crosshead 21 for rotatably connecting the piston rod 15 and the connecting rod 19. That is, the lower end of the piston rod 15 and the upper end of the connecting rod 19 are connected to the crosshead 21. On both sides (right and left in Fig. 2) of the crosshead 21, a pair of sliding plates 23 extending in the vertical direction are formed in a state fixed to the furniture 5 side.

3A and 3B schematically show the structure of the inner periphery of the cylinder of the diesel engine 1. As shown in the figure, the cylinder cover 11 is provided with a premixing fuel gas injection valve (hereinafter referred to as "premixed gas valve") 30 as a first fuel gas injection valve, (Hereinafter referred to as a "diffusion gas valve") 32 and a fuel oil injection valve (hereinafter referred to as "fuel oil valve") 34 as a valve are formed.

The premixed gas valve 30 is connected to an elongated supply source (not shown), and injects the fuel gas into the cylinder formed by the cylinder liner 9 and the cylinder cover 11 at a high pressure. As the fuel gas, a hydrocarbon-based gas such as vaporized LNG is used.

The gas injection pressure from the premixed gas valve 30 is, for example, 1.0 MPa or more and 50 MPa or less at absolute pressure, preferably 20 MPa or more and 30 MPa or less at absolute pressure. A plurality of injection holes are formed in the nozzles formed at the tip of the premixed gas valve 30, and fuel gas is injected from the respective injection holes into the cylinder. For example, in the example shown in Fig. 3B, a state in which the fuel gas is injected from each of the four injection holes is shown. As shown in this figure, the direction of the fuel gas injected from the premixed gas valve 30 is the direction of the piston 13, more specifically, the piston 13 after closing the scavenge pot 10 with the piston 13 That is, the top surface of the piston 13 toward the circular top surface.

The premixed gas valve 30 may be configured such that each injection hole is formed so that the fuel gas is injected from at least one injection hole toward the piston 13 and all the injection holes inject fuel gas toward the piston 13 Need not be formed.

The premixed gas valve 30 is activated when the diesel engine 1 is operated by premixed combustion (fuel gas premixed combustion) by the fuel gas, and the diffusion combustion operation by the fuel gas (Fuel oil diffusive combustion operation) by the fuel oil and the diffusion combustion operation by the fuel oil (fuel oil diffusive combustion operation). Starting and stopping of the premix gas valve 30 is carried out by a command from the control device 40 to be described later.

The injection timing of the premixed gas valve 30 is controlled by a control device 40 to be described later and is a range in which the fuel gas does not leak out of the system from the exhaust valve 12. Specifically, 20 deg BTDC (BTDC is Before Top Dead Center), preferably 100 or more and 60 deg BTDC or less. Here, the timing at which the exhaust valve 12 is closed is, for example, about 90 deg BTDC.

For example, when the load of the diesel engine 1 is 100%, the period for injecting the fuel gas (i.e., the period for continuously injecting the fuel gas) is 20 deg or more and 30 deg or less.

As shown in Fig. 3A, the diffusion gas valve 32 is formed on the outer peripheral side of the cylinder cover 11 when viewed in plan. The two diffusion gas valves 32 are disposed at positions facing each other with the center of the cylinder cover 11 (that is, the center of the exhaust valve 12) therebetween. The diffusion gas valve 32 and the premix gas valve 30 are disposed at positions shifted in the circumferential direction by a predetermined angle with respect to the premix gas valve 30 in the present embodiment, May be disposed on the cylinder cover 11. The number of the diffusion gas valves 32 is two as an example, and may be one or three or more, which is the same as the number of the fuel oil valves 34.

The diffusion gas valve 32 is connected to a fuel gas supply source (not shown), and injects the fuel gas into a cylinder formed by the cylinder liner 9 and the cylinder cover 11. Like the premixed gas valve 30, hydrocarbon gas such as vaporized LNG is used as the fuel gas.

The gas injection pressure from the diffusion gas valve 32 is 50 MPa or less, which is higher than the air (scavenging) after being compressed by the piston 13, and is 10 MPa or more and 30 MPa or less, for example, under an absolute pressure. A plurality of injection holes are formed in the nozzles formed at the tip of the diffusion gas valve 32, and the fuel gas is injected into the cylinder from each injection hole. The direction of the fuel gas injected from the diffusion gas valve 32 is slightly lower from the horizontal direction or from the horizontal direction so that the diffusive combustion by the fuel gas is performed in the combustion space where the piston 13 is raised to the vicinity of the top dead center, And is not directed to the top of the piston 13. [

The diffusion gas valve 32 is started when the diesel engine 1 is operated by diffusive combustion, and is stopped without starting in the premix combustion operation by the fuel gas or the diffusion combustion operation by the fuel oil. Starting and stopping of the diffusion gas valve 32 is carried out in accordance with a command from the control device 40 described later.

A period during which the diffusion gas valve 32 injects fuel gas (that is, a period during which the fuel gas is continuously injected) is controlled by a control unit (not shown). For example, when the load of the diesel engine 1 is 100% Or more.

As shown in Fig. 3A, when the cylinder cover 11 is seen in a plan view, the fuel oil valve 34 is located on the outer side of the exhaust valve 12 and also on the premixed gas valve 30 and the diffusion gas valve 32 Two on the inner circumferential side. The two fuel oil valves 34 are disposed at positions facing each other with the center of the cylinder cover 11 (that is, the center of the exhaust valve 12) therebetween. However, each fuel oil valve 34 is disposed at a position shifted in the circumferential direction by a predetermined angle with respect to the diffusion gas valve 32 and the premix gas valve 30. The number of the fuel oil valves 34 is only two as an example, and may be one or three or more. It should be noted that the inner circumferential side of the premixed gas valve 30 and the diffusion gas valve 32 may not be provided on the outer peripheral side of the exhaust valve 12.

The fuel oil valve 34 is connected to a fuel oil supply source (not shown), and injects fuel oil into a cylinder formed by the cylinder liner 9 and the cylinder cover 11. [ As the fuel flow path, for example, heavy oil having a relatively high ratio of residual oil such as C heavy oil (90% or more of which is residual oil) referred to in Japanese JIS standard is used.

The injection pressure from the fuel oil valve 34 is higher than air (scavenging) after being compressed by the piston 13, for example, 30 MPa or more and 80 MPa or less at absolute pressure. A plurality of injection holes are formed in the nozzles formed at the tip of the fuel oil valve 34, and fuel oil is injected from each injection hole into the cylinder. For example, the direction of the fuel oil injected from the fuel oil valve 34 is slightly shifted from the horizontal direction or the horizontal direction so that the ignition or the diffusion combustion is performed in the combustion space in which the piston 13 is raised to the vicinity of the top dead center, Down direction and is not directed toward the top of the piston 13. [

When the diesel engine 1 is operated by diffusive combustion by the fuel oil, the fuel oil valve 34 is operated to inject fuel oil for diffusive combustion (so-called oil burner operation) During the combustion operation and the diffusive combustion operation by the fuel gas, it operates to inject the pilot oil for ignition. The operation of the fuel oil valve 34 is carried out in accordance with a command from a control unit (not shown).

[Operation mode as dual fuel engine]

Next, the operation mode of the diesel engine 1 having the above-described configuration will be described. The engine 1 is operated by appropriately switching the fuel gas operation and the fuel oil operation. In the fuel gas operation, the fuel gas diffusion combustion system, the fuel gas preblend combustion system, the fuel gas partial premix combustion system 3 The branch combustion method is selectively used, and the fuel oil operation uses the fuel oil diffusion combustion method.

The operation modes of the dual fuel engine include a fully pre-mixed fuel gas mode in which a fuel gas pre-mixed combustion mode in which a fuel gas is combusted in a fuel gas premix combustion manner, and a fuel gas diffusion combustion mode And a partial fuel gas partial combustion mode in which a part of the fuel gas is burned in a premixed combustion mode and a remaining portion of the fuel gas is used in a diffusive combustion mode, There is a gas mode and a diffusive fuel oil mode (so-called oil burning mode) in which fuel oil is used to burn by a fuel oil diffusive combustion method. When the diffusive combustion or the diffusive combustion system is not distinguished from the fuel gas diffusive combustion or the fuel oil diffusive combustion, it is also referred to simply as a diffusive combustion or diffusive combustion system. The fuel gas premix combustion system is a combustion system that uses at least the premix gas valve 30 for fuel supply, and includes a fuel gas preblend combustion system and a fuel gas partial premix combustion system. That is, the fuel gas pre-mixed combustion system broadly represents a combustion system that uses a fuel gas to burn by a premixed combustion system. The fuel gas pre-mixed combustion system and either or both of the fuel gas pre- .

In the fully pre-mixed fuel gas mode, the premixed gas valve 30 is used for fuel supply and the fuel oil valve 34 is used for pilot.

In the diffusion fuel gas mode, the diffusion gas valve 32 is used for fuel supply and the fuel oil valve 34 is used for pilot.

In the partial premixed fuel gas mode, the premixed gas valve 30 is used as a fuel supply and the fuel oil valve 34 is used as a pilot for combustion in the fuel gas premix combustion mode, The diffusion gas valve 32 is used for fuel supply and the fuel oil valve 34 is used for pilot.

In the diffusive fuel oil mode, only the fuel oil valve 34 is used.

The pre-mixed fuel gas mode is preferable when the ship navigates within, for example, an ECA (air pollutant emission control area, simply referred to as an emission control area) because the NOx emission amount is small. However, in the fully pre-mixed fuel gas mode, abnormal combustion such as over-ignition and knocking is likely to occur, and in order to avoid this, it is necessary to lower the compression ratio in comparison with the normal (diffusive combustion type) case. If the compression ratio is lowered, the maximum output is limited.

The diffusion fuel gas mode can adopt a high compression ratio because it has higher combustion stability than the premixed fuel gas mode. On the other hand, since the NOx generation amount is larger than the pre-mixed fuel gas mode, for example, Used to navigate. However, since the diffusion fuel gas mode has a small amount of SOx generation as in the case of the diffusion fuel mode, if the combustion stability is required within a predetermined time within a range not exceeding the NOx regulated amount even in the ECA, Can be used instead.

The diffusive fuel oil mode can adopt a high compression ratio because the combustion stability is higher, but a large amount of SOx derived from the fuel oil occurs in comparison with the case where the fuel gas is used. Thus, for example, when the SOx emission control is performed in a relatively loose area, higher combustion stability is required, or when fuel oil is better than fuel gas is used.

(Fully premixed fuel gas mode)

The entirely mixed fuel gas mode will be described.

As shown in Figs. 3A and 3B, at the beginning of the compression stroke after the exhaust valve 12 is closed and the piston 13 closes the scavenging port 10, 30 at an absolute pressure of not less than 1.0 MPa and not more than 50 MPa, preferably not less than 20 MPa and not more than 30 MPa as absolute pressure, toward the top of the piston 13. [ Further, in the fully mixed fuel gas mode, the diffusion gas valve 32 is closed, and the fuel gas is injected from the premix gas valve 30 only. The single-stage diffusion gas valve 32 may be used in combination.

The injection timing of the fuel gas from the premixed gas valve 30 is set to a range in which the engine 10 is closed after the piston 13 is closed and the fuel gas does not leak from the exhaust valve 12 to the outside of the system For example, between 140 and 20 deg BTDC, preferably between 100 and 60 deg BTDC. In this case, the timing at which the exhaust valve 12 is closed is about 90 deg BTDC. The injection period in which the fuel gas is continuously injected from the premix gas valve 30 is 20 deg or more and 30 deg or less when the load of the internal combustion engine is 100%, for example.

Since the premixed gas valve 30 is sprayed from the upper cylinder cover 11 toward the top of the piston 13 underneath, the premixed gas valve 30 is moved in the longitudinally long combustion space after the scavenge pot 10 is closed by the piston 13 The longitudinal direction can be effectively used to inject the fuel gas as a whole, and the mixing of the fuel gas with the air (scavenging; oxidizing agent gas) is promoted. Particularly, since the diesel engine 1 of this embodiment is an ultra long stroke, mixing by longitudinally injecting fuel gas is effective.

After the premixture is formed in the cylinder by the fuel gas injected from the premixed gas valve 30, the piston 13 moves upward to compress the pre-mixer. When reaching the vicinity of the top dead center, pilot oil is injected from the fuel oil valve 34 to be ignited. Premixed combustion is carried out while the flame formed by this ignition propagates in the premixer, and combustion and expansion strokes are performed (at this time, the injection of pilot oil from the fuel oil valve 34 is stopped), the piston 13 Move downward.

(Diffusion fuel gas mode)

The diffusion fuel gas mode will be described.

In the compression stroke after the exhaust valve 12 is closed and the piston 13 closes the scavenging port 10, only the air introduced from the scavenge port 10 is compressed. When the piston 13 reaches the vicinity of the top dead center, the fuel oil is injected from the fuel oil valve 34 as pilot oil, and simultaneously with or immediately after the pilot oil flows from the diffusion gas valve 32, More preferably not less than 50 MPa (absolute pressure), more preferably not less than 10 MPa and not more than 30 MPa as absolute pressure. Thereby, diffusion combustion is performed in the cylinder according to the injection of the fuel gas (at this time, the injection of the pilot oil from the fuel oil valve 34 is stopped), and the piston 13 is pushed downward by the expansion stroke.

Further, in the diffusion fuel gas mode, the premix gas valve 30 is always closed.

(Partial premixed fuel gas mode)

The partial premixed fuel gas mode will be described.

In the partial premixed fuel gas mode, a portion of the fuel gas is injected from the premixed gas valve 30 toward the top of the piston 13 at the same absolute pressure and timing as the fully pre-mixed fuel gas mode. At this time, the diffusion gas valve 32 is closed. Thereafter, the remaining fuel gas is injected from the diffusion gas valve 32 at the same absolute pressure and timing as the diffusion fuel gas mode. At this time, the premix gas valve 30 is closed.

(Diffusion fuel oil mode)

The diffusing fuel oil mode (so-called oil burning mode) is the same as the diffusive combustion using common fuel oil (not shown). Concretely, the exhaust valve 12 is closed to compress the air with the rise of the piston 13, and the fuel oil is injected from the fuel oil valve 34 at a high pressure in the vicinity of the top dead point for diffusion combustion And the piston 13 is lowered by the expansion stroke by the diffusive combustion.

By providing the diffusion fuel oil mode in this manner, the diesel engine 1 can be established as a dual fuel engine (DF engine) that is used in combination with the operation using the fuel gas.

In the diffusion fuel oil mode, the premixed gas valve 30 and the diffusion gas valve 32 are always closed.

(Premixed transition control)

The engine 1 of the present embodiment is further provided with a premixing transition control performed when the transition from the diffusion fuel gas mode or the diffusion fuel oil mode to the fully-pre-mixed fuel gas mode or the partial premixed-fuel gas mode is performed.

When switching from the diffusion fuel gas mode using the fuel gas to the all-premixed fuel gas mode or the partial premixed fuel gas mode, the fuel gas injected from the diffusion gas injection valve 32 is reduced and the premixed gas valve 30 The fuel gas being injected from the fuel cell. That is, at the time of switching from the diffusive fuel gas mode to the premixed fuel gas mode, the premixing ratio which is the ratio of the fuel gas injected from the premix gas valve 30 among all the injecting fuel gas is 0% (A predetermined percentage set in the case of the partial premixed fuel gas mode in which the premixed combustion and the diffusive combustion are used in combination) in a predetermined ratio (100% in the case of the premixed combustion only fuel gas mode only) . At this time, in the combustion stroke in the first cycle immediately after the transition from the diffusion fuel gas mode to the premixed fuel gas mode, the fuel gas injected from the premixed gas valve 30 The amount of the fuel gas injected from the premix gas valve 30 is increased to the concentration at which the mixture is completely burned to increase the premixing ratio at once. More specifically, the preliminary mixing ratio is increased from 0% to 40% or more and 60% or less in a first cycle at the time of mode switching. Then, after the preliminary mixing ratio is set to 40% or more and 60% or less in the first cycle immediately after the mode change, the preliminary mixing ratio is gradually increased toward a predetermined ratio in a plurality of subsequent cycles.

Thus, at the time of switching from the diffusive fuel gas mode to the premixed fuel gas mode, the premixed fuel is completely burned from the first cycle, and the unburned gas is prevented from being discharged from the exhaust valve 12 . That is, if the premixing ratio is gradually increased from 0% immediately after the mode change to a plurality of cycles, the amount of the fuel gas injected from the premix gas valve 30 is small and the premix concentration is too low It is possible to avoid the problem that the hydrocarbon gas HC as the unburned fuel gas is discharged from the exhaust valve 12 because the fuel gas can not be completely combusted.

The same control is also performed at the time of switching from the diffusion fuel oil mode using the fuel oil to the premixed fuel gas mode. That is, when switching from the diffusive fuel oil mode to the mixed fuel gas mode, the fuel oil injected from the fuel oil valve 34 is decreased while the fuel gas injected from the premix gas valve 30 is increased. That is, at the time of switching from the diffusive fuel oil mode to the premixed fuel gas mode, the premixing ratio, which is the ratio of the amount of heat generated by the fuel gas injected from the premixed gas valve 30, is 0% (A predetermined percentage set in the case of the partial premixed fuel gas mode in which the premixed combustion and the diffusive combustion are jointly used) at a predetermined ratio (100% in the case of the premixed combustion gas mode only) I will. At this time, in the combustion stroke in the first cycle immediately after the transition from the diffusive fuel oil mode to the premixed fuel gas mode, the fuel gas injected from the premixed gas valve 30 The amount of the fuel gas injected from the premix gas valve 30 is increased to the concentration at which the mixture is completely burned to increase the premixing ratio at once. More specifically, the preliminary mixing ratio is increased from 0% to 40% or more and 60% or less in a first cycle at the time of mode switching. Then, after the preliminary mixing ratio is set to 40% or more and 60% or less in the first cycle immediately after the mode change, the preliminary mixing ratio is gradually increased in the subsequent plural cycles.

Thus, at the time of switching from the diffusive fuel oil mode to the premixed fuel gas mode, the premixed fuel is completely burned from the first cycle, and the unburned gas can be prevented from being discharged from the exhaust valve 12. That is, if the premixing ratio is gradually increased from 0% immediately after the mode change to a plurality of cycles, the amount of the fuel gas injected from the premix gas valve 30 is small and the premix concentration is too low It is possible to avoid the problem that the hydrocarbon gas HC as the unburned fuel gas is discharged from the exhaust valve 12 because the fuel gas can not be completely combusted.

[Control by control device of dual fuel engine]

Here, the control by the control device 40 of the dual fuel engine according to the present embodiment will be described with reference to Fig. 1. Fig.

1, the present control device 40 is provided with a judging section 42 for judging whether or not the engine 1 is in an exhaust gas regulating state in which exhaust gas should be regulated, An operation mode selection unit (combustion mode selection means) 44 for appropriately selecting and setting the operation mode (combustion mode) during operation, a fuel injection control unit An actual compression ratio control unit (actual compression ratio control means) 48 for controlling the actual compression ratio to be a real compression ratio corresponding to the selected operating mode, And a boost control section (boost control section) 50 as functional elements.

First, determination by the determination section 42 will be described. The judging unit 42 judges whether or not the marine area on which the marine vessel on which the marine vessel 1 is mounted is an exhaust gas regulating area. If the marine area is in the exhaust gas regulating area, the engine 1 is in a state The determination of the navigation area can be made from the positional information of the ship, for example, from GPS or the like, and from the information of the positional information and the pre-stored exhaust control area.

When the determination section 42 determines that the marine navigation area of the ship is in the exhaust control area (the engine 1 is in the exhaust regulation state), the operation mode selection section 44 selects either the fully mixed fuel gas mode or the partial example When the judging unit 42 judges that the marine area of the ship is not in the exhaust control area (the engine 1 is not in the exhaust regulation state), the mixed fuel gas mode is selected and the diffusion fuel mode or the diffusion fuel gas mode As shown in FIG.

The fuel injection control section 46 controls the fuel injection to be the fuel injection mode corresponding to the operation mode set by the operation mode selection section 44. [ In short, when the fully pre-mixed fuel gas mode is set, fuel injection is performed by using the premixed gas valve 30 as the fuel supply and the fuel oil valve 34 as the pilot, as described above. When the partial premixed fuel gas mode is set, the premixed gas valve 30 and the diffusion gas valve 32 are used for fuel supply and the fuel oil valve 34 is used for pilot injection, as described above, . Further, when the diffusion fuel gas mode is set, the diffusion gas valve 32 is used for fuel supply and the fuel oil valve 34 is used for pilot fuel injection, as described above. When the diffusion fuel oil mode is set, the fuel injection is performed using the fuel oil valve 34 as described above.

The actual compression ratio control unit 48 controls the actual compression ratio in accordance with the operation mode set by the operation mode selection unit 44. That is, when the fully pre-mixed fuel gas mode or the partially pre-mixed fuel gas mode is set, the actual compression ratio is controlled to a low compression ratio, and when the diffusion fuel gas mode or the diffusion fuel mode is set, the actual compression ratio is controlled at a high compression ratio.

Here, control of the actual compression ratio by the actual compression ratio control unit 48 will be described.

As described above, in the fully pre-mixed fuel gas mode or the partially premixed fuel gas mode, the premixed gas valve 30 is used to control the piston 13 after the scavenge pot 10 is closed by the piston 13, (For example, upward and downward directions) of the combustion space after the scavenge openings 10 are closed by the pistons 13 by injecting the fuel gas toward the front side (for example, from the upper side to the lower side) So that the fuel gas can be injected to the whole, and the mixing of the fuel gas with the oxidant gas can be promoted.

Accordingly, the local minimum? (? Is excess air ratio) at which the fuel gas concentration is locally increased can be increased, and abnormal combustion such as overcharge ignition and knocking can be avoided as much as possible, thereby improving combustion stability. In addition, since abnormal combustion such as over-ignition and knocking can be avoided as much as possible, the lowering value of the compression ratio can be made smaller than that of the conventional pre-mixing engine and the deterioration of thermal efficiency can be minimized, It is also possible to operate at a high load of an effective pressure).

However, even if the lowering value of the compression ratio can be made smaller than that of the conventional pre-mixing engine, in order to increase the heat efficiency of the engine 1 in the diffusion fuel oil mode or the diffusion fuel gas mode, The compression ratio adoptable in the mixed fuel gas mode or the partial premixed fuel gas mode is insufficient, so it is necessary to use a higher compression ratio.

Thus, the engine 1 is configured so that the actual compression ratio can be changed during operation of the engine 1. [

In the present embodiment, this actual compression ratio is changed by changing the timing of discontinuing the exhaust valve 12. In other words, by delaying the timing of closing the exhaust valve 12 (that is, by cranking), the capacity of the cylinder at the time of starting actual compression of the engine 1 becomes small, and the actual compression ratio can be reduced. Conversely, by advancing (or advancing) the closing timing of the exhaust valve 12, the capacity of the cylinder at the time of starting actual compression of the engine 1 becomes larger, and the actual compression ratio can be increased.

Therefore, the engine 1 is provided with a dynamic valve device (variable valve-operated valve device) 12A capable of changing at least the closing timing of the exhaust valve 12. The valve device 12A is a so-called camless valve device for controlling the exhaust valve 12 by an actuator (not shown). By controlling the operation of the actuator by the control device 40, the exhaust valve 12 Can be easily changed. It should be noted that a mechanical variable valve mechanism of the engine 1 may be used for the variable valve-driven valve device.

The supercharging control unit (50) controls the supercharging amount in accordance with the operation mode set by the operation mode selecting unit (44). That is, when the diffusive fuel gas mode or the diffusive fuel oil mode is set at least in a high load state where the load of the engine 1 is larger than the predetermined load, the supercharging amount is set to the normal state, When the pre-mixed fuel gas mode is set, the boost level is increased.

This is because, when the total pre-mixture fuel gas mode or the partial premixed fuel gas mode is set as described above, the amount of air trapped in the cylinder is reduced when the actual compression ratio is reduced by changing the closing timing of the exhaust valve 12 The maximum output of the engine 1 is limited. Therefore, in this embodiment, the supercharger of the supercharger 16 is increased to increase the amount of air trapped in the cylinder, thereby improving the maximum output of the engine 1 will be.

4 is a time chart illustrating a change in the timing of discontinuation of the exhaust valve 12. The timing of opening and closing of the scavenging port 10 and the timing of opening and closing of the exhaust valve 12, Together with the timing. As shown in Fig. 4, as the piston 13 moves from the TDC to the bottom dead center BDC, the cylinder internal pressure decreases. When the exhaust valve 12 is opened at the time t1, However, when the scavenging port 10 is opened at the time point t2, the piston 13 reaches the bottom dead center BDC while the internal pressure is slightly recovered. When the scavenging port 10 is closed at the time t3 and the exhaust valve 12 is then closed at the time point t4, the internal pressure of the piston 13 is increased as the piston 13 moves toward the top dead center TDC.

The opening and closing timings of the normal exhaust valve 12 are indicated by solid lines and the actual compression ratio can be lowered by delaying the exhaust timing of the exhaust valve 12 from time t4 to time t5. At the same time, however, the cylinder inner pressure is lowered from the level (diffusive combustion) of the normal disposal timing shown by the solid line to the two-dot chain line (premix combustion 2). Therefore, the amount of air trapped in the cylinder is reduced. On the other hand, by increasing the supercharger amount of the supercharger 16, the amount of air trapped in the cylinder is increased, and as a result, the cylinder inner pressure is restored as shown by the broken line (premix combustion 1).

The control of the supercharge amount of the supercharger 16 by the supercharging controller 50 will be described in detail.

In the present embodiment, the turbocharger 16 equipped in the engine 1 is configured such that two superchargers 16A and 16B are connected in series and the two-stage supercharger and the supercharger are switched by switching the valves.

That is, the compressor 16AC of the first turbocharger 16A on the downstream side of the exhaust passage and the compressor 16BC of the second turbocharger 16B on the downstream side of the exhaust passage and on the upstream side of the exhaust passage, An exhaust connecting passage 162a is formed between the exhaust turbine 16AT of the first turbocharger 16A and the exhaust turbine 16BT of the second turbocharger 16B do. A gas connection passage 161b is formed between the compressor 16AC of the first turbocharger 16A and the scavenging manifold 20 (see Fig. 2), and the exhaust turbine 16AT of the first turbocharger 16A, And an exhaust connection passage 162b is formed between the exhaust manifold 14 and the exhaust manifold 14 (see Fig. 2). Between the compressor 16BC of the second turbocharger 16B and the scavenge manifold 20 is connected a scavenge connection passage 161c and the exhaust turbine 16BT of the second turbocharger 16B and the exhaust manifold 14, an exhaust connection passage 162c is formed.

Further, the air coolers 18 are formed in the respective connection passages 161b and 161c. The air coolers 18 of the connection passages 161b and 161c are also usable.

Off valves 163a to 163c are installed in the exhaust passages 161a to 161c and the exhaust connection passages 163a to 163c are provided with open / close valves 164a to 164c interposed therebetween .

When the open / close valves 163b and 164b are closed and the open / close valves 163a and 163c and 164a and 164c are opened, the exhaust gas discharged from the engine 1 flows from the exhaust manifold 14 to the second turbocharger 16B The exhaust turbine 16BT and the exhaust turbine 16AT of the first supercharger 16A while being driven to rotate the exhaust turbines 16BT and 16AT. As a result, the compressors 16AC and 16BC are rotationally driven to pressurize the purge air in two stages.

When the open / close valves 163a, 163c and 164a, 164c are closed, the open / close valves 163b, 164b are opened and the exhaust gas discharged from the engine 1 is exhausted from the exhaust manifold 14 to the first turbocharger 16A And is exhausted through the exhaust turbine 16AT, thereby rotationally driving the exhaust turbine 16AT. Thereby, the compressor 16AC is rotationally driven, and once pressurizes the air for combustion.

In this way, when the pre-mixture fuel gas mode or the partial premixed fuel gas mode is set, the actual compression ratio is reduced by changing the closing timing of the exhaust valve 12, while suppressing abnormal combustion such as over- Thus, the reduction in the amount of air trapped in the cylinder is compensated for by increasing the boost pressure by the second-stage supercharging, thereby improving the maximum output of the engine 1. [

When the diffuser fuel gas mode or the diffusive fuel oil mode is set in the supercharging control unit 50, when the load of the engine 1 is in the high load state, the supercharger is once set to the normal state by the supercharger, It is difficult to increase the supercharging amount due to the second stage supercharging at the time of high load. In the case where the load of the engine 1 is at the low load state below the predetermined load, since the supercharging amount by the second stage supercharger can be expected, We perform second stage supercharge.

Since the control apparatus for a dual fuel engine and the ship having the dual fuel engine according to the first embodiment of the present invention are constructed as described above, when the ship enters the exhaust control area, The fuel gas mode is selected so that the ship can be operated in a state in which the exhaust regulation is cleared with a small NOx emission amount. Further, when the ship escapes from the exhaust control area, the diffusion fuel gas mode or the diffusion fuel mode is selected, and the ship can be operated in a state in which a large maximum output can be obtained with high efficiency.

In this control device, the actual compression ratio is lowered particularly in the fully pre-mixed fuel gas mode or the partially premixed fuel gas mode, and the actual compression ratio is increased in the diffusive fuel gas mode or the diffusive fuel oil mode. And the operation in the diffusive fuel gas mode or the diffusive fuel oil mode in which a large maximum output can be obtained with high efficiency by increasing the actual compression ratio.

In addition, when the pre-mixture fuel gas mode or the partial premixed fuel gas mode is set, if the actual compression ratio is reduced by changing the timing of elimination of the exhaust valve 12, the amount of air trapped in the cylinder decreases, However, in this embodiment, since the supercharger of the supercharger 16 is increased to increase the amount of air trapped in the cylinder, it is possible to increase the amount of air trapped in the pre-mix fuel gas mode or the partial premix fuel gas mode The maximum output of the engine 1 in the engine 1 can be improved.

[Second Embodiment]

Next, a second embodiment of the present invention will be described.

The present embodiment is different from the first embodiment only in the configuration of the supercharger 16 capable of increasing / reducing the supercharge amount.

As shown in Fig. 5, the supercharger 16 has a first supercharger 16C and a second supercharger 16D formed in parallel. A connecting passage 165a is formed between the compressor 16CC and the scavenge manifold 20 of the first turbocharger 16C so that the exhaust turbine 16CT of the first turbocharger 16C and the exhaust manifold 14 of the first turbo- An exhaust connection passage 166a is formed. Between the compressor 16DC of the second turbocharger 16D and the scavenge manifold 20 is formed a scavenge connection passage 165b and the exhaust turbine 16DT of the second turbocharger 16D and the exhaust manifold 14, an exhaust connection passage 166b is formed.

An air cooler 18 is formed in each of the heater connection passages 165a and 165b.

Closing valves 167 and 168 are interposed between the intake passage 165b and the exhaust passage 166b.

Although the first supercharger 16C is always in operation, the second turbocharger 16D operates when the open / close valves 167 and 168 are opened, and stops when the open / close valves 167 and 168 are closed.

Since the exhaust pressure is low at the bottom of the engine 1, the exhaust pressure is concentratedly used only by the first turbocharger 16C. When the engine 1 is loaded at high load, the exhaust pressure of the first turbocharger 16C is high, The supercharging amount can be increased by effectively using the exhaust pressure by using both the first supercharger 16D and the second supercharger 16D.

In the present embodiment, when the fully pre-mixed fuel gas mode or the partially pre-mixed fuel gas mode is set, the total pre-mixed fuel gas mode or the partial pre-mixed fuel gas mode is set so that the amount of air trapped in the cylinder is reduced. The supercharger is increased by using both the first turbocharger 16C and the second turbocharger 16D when the engine 1 is under a high load. Also, in the diffusive fuel gas mode or the diffusive fuel oil mode, when both the first turbocharger 16C and the second turbocharger 16D are used, the supercharger is excessively large. Therefore, even when the engine 1 is loaded at high load, 16C).

The control system for a dual fuel engine according to the second embodiment of the present invention and the ship having the dual fuel engine control system according to the second embodiment of the present invention are constructed as described above. Therefore, as in the first embodiment, The mixed fuel gas mode or the partially premixed fuel gas mode is selected so that the ship is operated in a state in which the exhaust regulation is cleared with the NOx emission amount being small and the ship escapes the exhaust control zone, Mode is selected so that the ship can be operated in a state in which a large maximum output can be obtained with high efficiency.

In addition, since the actual compression ratio is lowered in the fully pre-mixed fuel gas mode or the partially premixed fuel gas mode and the actual compression ratio is increased in the diffusive fuel gas mode or the diffusive fuel oil mode, as in the first embodiment, The operation in the mixed fuel gas mode or the partially premixed fuel gas mode and the operation in the diffusive fuel gas mode or the diffusive fuel oil mode in which a large maximum output can be obtained with high efficiency by raising the actual compression ratio can be compatible.

By increasing the amount of air trapped in the cylinder by increasing the supercharger amount of the turbocharger 16 when the all-preliminary fuel gas mode or the partial premixed fuel gas mode is set, The maximum output of the engine 1 in the fuel gas mode can be improved.

 [Other]

Although the embodiments of the present invention have been described above, the present invention can be carried out with various modifications of the above-described embodiments within the scope not departing from the spirit of the present invention.

For example, as the turbocharger 16 capable of increasing the superheated amount in the fully pre-mixed fuel gas mode or the partially pre-mixed fuel gas mode, for example, a motor-assisted supercharger may be applied, The electric power assist may be used to increase the supercharge amount. In addition, it is also possible to increase the supercharger by increasing the capacity in the premixed fuel gas mode by applying a capacity variable supercharger.

In the above embodiment, the control device 40 determines whether or not the marine navigation zone on which the vessel is navigating is within the exhaust control zone, and automatically selects the operation mode (combustion mode) of the engine 1. However, (Combustion mode selection means) of the control device 40 is set to the fully mixed fuel gas mode (the mode for selecting the combustion mode) (The fuel gas pre-mixed combustion mode) or the partial premixed fuel gas mode (the fuel gas partial premixed combustion mode), and when the exhaust gas is not in the regulated area, (The combustion mode selection means) may be manually instructed to select the diffusion fuel gas mode or the diffusion fuel use mode (fuel gas diffusion combustion system) manually.

In the above-described embodiment, the present invention is exemplified by a dual fuel engine as the internal combustion engine. However, the internal combustion engine related to the present invention can be at least selected from the fuel gas diffusion combustion system and the fuel gas premix combustion system during operation, The fuel gas diffusing combustion system, the fuel gas all-premixed combustion system and the fuel gas partial premixed combustion system must be selectable at the time of operation, and it is not limited to the dual fuel engine, but may be an internal combustion engine ).

During operation of the internal combustion engine, at least one of the combustion modes including the fuel gas diffusion combustion mode and the fuel gas premixed combustion mode, or at least the fuel gas diffusion combustion mode and the fuel gas all- A combustion mode selection process for selecting one of the combustion modes including the fuel gas partial premixed combustion mode and a compression ratio control process for controlling the actual compression ratio of the internal combustion engine according to the combustion mode selected in the combustion mode selection process , It is possible to operate the engine in the direction of canceling the change in engine performance accompanied by the change of the combustion mode by controlling the actual compression ratio.

1: Dual fuel engine (internal combustion engine)
9: Cylinder liner
10: Scavenge port
11: Cylinder cover
12: Exhaust valve
13: Piston
14: Exhaust gas manifold
16: supercharger
30: Premix gas valve (first fuel gas injection valve)
32: Diffusion gas valve (second fuel gas injection valve)
34: Fuel oil valve (fuel oil injection valve)
40: Control device
42: judgment section (judgment means)
44: Operation mode selection unit (combustion mode selection means)
46: fuel injection control unit (fuel injection control means)
48: Actual compression ratio control section (actual compression ratio control means)
50: a boost control section (boost control means)

Claims (11)

A combustion mode selecting means capable of selecting at least a fuel gas diffusion combustion mode and a fuel gas premixed combustion mode during operation of the internal combustion engine,
Fuel injection control means for controlling the fuel injection to be in a fuel injection mode according to the combustion mode selected by the combustion mode selection means;
A real compression ratio control means for controlling the actual compression ratio to be a real compression ratio according to the combustion mode selected by the combustion mode selection means,
And determination means for determining whether or not the exhaust gas is in a regulated state in which exhaust of the internal combustion engine is to be regulated,
Wherein the combustion mode selection means selects the fuel gas premix combustion mode when it is determined by the determination means that the exhaust gas is regulated, and when the determination means determines that the mode is not the exhaust gas regulation mode, Select,
Wherein the actual compression ratio control means controls the actual compression ratio to a lower compression ratio than that of the fuel gas diffusion combustion system when the fuel gas premix combustion mode is selected and controls the actual compression ratio Wherein the control is performed at a higher compression ratio ratio than in the case of the fuel gas premix combustion method. The method according to claim 1,
The fuel gas premix combustion system includes a fuel gas preblend combustion system in which fuel gas is combusted only in a fuel gas premix combustion mode, a fuel gas preblend combustion system in which a part of the fuel gas is premixed, Including mixed combustion mode,
Wherein the combustion mode selection means is capable of selecting at least the fuel gas diffusion combustion mode, the fuel gas all premix combustion mode and the fuel gas partial premixed combustion mode during operation of the internal combustion engine,
Wherein the actual compression ratio control means controls the actual compression ratio to the low compression ratio when the fuel gas pre-mixed combustion method or the fuel gas partial premixed combustion method is selected, and when the fuel gas diffusion combustion mode is selected, Is controlled by the high-compression ratio. 3. The method according to claim 1 or 2,
The internal combustion engine includes a valve device capable of changing an exhaust valve closing timing,
Wherein the actual compression ratio control means controls the actual compression ratio by operating the exhaust valve closing timing and controls the timing at which the exhaust valve is closed to the retarded side when the actual compression ratio is set to the low compression ratio, And the exhaust valve closing timing is controlled to be more advanced than the case where the exhaust valve closing timing is set to the low compression ratio when the actual compression ratio is set to the high compression ratio. 4. The method according to any one of claims 1 to 3,
Wherein the internal combustion engine includes a supercharger capable of increasing and decreasing a supercharging amount,
Wherein when the combustion mode selecting means selects the fuel gas diffusion combustion mode in a case of a high load state in which the load of the internal combustion engine is higher than a predetermined load, the supercharging amount is set to a normal state, And a supercharging control means for increasing the supercharged amount to an increased state than the normal state when the premixed combustion mode is selected. 5. The method of claim 4,
The supercharger is a supercharger capable of switching two-stage supercharger and supercharger once,
Wherein said supercharger control means sets the supercharger once as a supercharger when the supercharger is in the normal state and controls the supercharger as a supercharger in the second stage when the supercharger is in the increased state, Device. The method according to claim 4 or 5,
The supercharging control means sets the supercharging amount to the increased state when the load of the internal combustion engine is a low load state under the predetermined load when the combustion mode selecting means selects the fuel gas diffusion combustion system And a control unit for controlling the internal combustion engine. 7. The method according to any one of claims 1 to 6,
The internal combustion engine is a marine engine equipped on a ship,
Wherein the judging means judges that the marine vessel is in the exhaust regulation state if the maritime area in which the marine vessel is navigating is within the exhaust gas regulation area and judges that the marine area is not the exhaust regulation state when the marine area is outside the exhaust regulation sea area Control device for internal combustion engine. 8. A watercraft comprising an internal combustion engine control device according to any one of claims 1 to 7 and an internal combustion engine controlled by the control device. A judging step of judging whether or not the exhaust gas is in a regulated state in which exhaust of the internal combustion engine should be regulated,
Wherein when the internal combustion engine is in the exhaust-gas regulating state, the internal combustion engine is operated in at least one of a combustion mode including a fuel gas diffusion combustion mode and a fuel gas premixed combustion mode, A combustion mode selection step of selecting the fuel gas diffusion combustion mode when it is determined that the combustion mode is not the exhaust gas regulation mode by the determination step,
And a compression ratio control step of controlling the actual compression ratio of the internal combustion engine according to the combustion mode selected in the combustion mode selection step. 10. The method of claim 9,
The fuel gas premix combustion system includes a fuel gas preblend combustion system in which fuel gas is combusted only in a fuel gas premix combustion mode, a fuel gas preblend combustion system in which a part of the fuel gas is premixed, Including mixed combustion mode,
In the combustion mode selection step, during operation of the internal combustion engine, at least one of the fuel gas diffusion combustion mode, the fuel gas all premix combustion mode, and the fuel gas partial premixed combustion mode And the combustion mode is selected. 11. The method according to claim 9 or 10,
The internal combustion engine is a marine engine equipped on a ship,
Wherein the determination step determines that the marine vessel is in the exhaust regulation state if the maritime area in which the vessel is navigating is within the exhaust control area and determines that the marine area is not in the exhaust regulation state if the marine area is outside the exhaust regulation area Operation method of internal combustion engine.

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