CN107250515B

CN107250515B - Control device for internal combustion engine, ship provided with same, and method for operating internal combustion engine

Info

Publication number: CN107250515B
Application number: CN201580076408.XA
Authority: CN
Inventors: 石田裕幸; 三柳晃洋; 平冈直大; 驹田耕之
Original assignee: Mitsubishi Heavy Industries Ltd; Japan Engine Corp
Current assignee: Mitsubishi Heavy Industries Ltd; Japan Engine Corp
Priority date: 2015-02-27
Filing date: 2015-08-06
Publication date: 2020-09-15
Anticipated expiration: 2035-08-06
Also published as: WO2016136001A1; KR101953050B1; CN107250515A; JP6412243B2; KR20170102551A; JPWO2016136001A1

Abstract

A control device for an internal combustion engine, comprising: a combustion mode selection means (44) capable of selecting at least a fuel gas diffusion combustion mode and a fuel gas premix combustion mode during operation of the internal combustion engine; a fuel injection control means (46) for controlling fuel injection so that the fuel injection is in a fuel injection mode corresponding to the selected combustion mode; and an actual compression ratio changing means (48) that changes the actual compression ratio based on the selected combustion mode, wherein during operation of the internal combustion engine, the actual compression ratio changing means (48) changes the actual compression ratio to a low compression ratio if switching to the fuel gas premixed combustion mode, and the actual compression ratio changing means (48) changes the actual compression ratio to a high compression ratio if switching to the fuel gas diffusion combustion mode. In the exhaust gas restriction strengthening sea area, the engine can suppress the discharge of NOx without using an additional device, and in other sea areas, the output of the engine can be ensured.

Description

Control device for internal combustion engine, ship provided with same, and method for operating internal combustion engine

Technical Field

The present invention relates to a control device for an internal combustion engine that performs premixed combustion using fuel gas, a ship provided with the control device for an internal combustion engine, and an operation method for an internal combustion engine.

Background

In recent years, a dual-fuel internal combustion engine (hereinafter, also referred to as a "DF internal combustion engine") applicable to a marine low-speed two-stroke diesel engine has been developed (see patent documents 1 and 2 below). The operation mode of the DF internal combustion engine includes a fuel operation for combusting fuel and a fuel gas operation for combusting fuel gas such as LNG as in the conventional art. In addition, fuel gas operation generally uses fuel oil as a pilot fuel for ignition.

In such a DF internal combustion engine, a fuel diffusion combustion method of performing diffusion combustion of fuel is generally adopted in the fuel operation, but two combustion methods, a fuel gas diffusion combustion method of performing diffusion combustion of fuel gas and a fuel gas premix combustion method of performing premix combustion of fuel gas, can be adopted in the fuel operation.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5395848

Patent document 2: international publication No. 2013/183737A1

Technical problem to be solved by the invention

However, according to the premix method, EGR and SCR for reducing harmful NOx emission are not required. However, the premixing system is likely to cause abnormal combustion such as preignition and knocking, and in order to avoid this problem, the compression ratio has to be lowered compared to a normal diesel engine. Therefore, the premixing method has a problem in that the maximum output is limited. Even when the fuel operation is performed by the DF internal combustion engine having a reduced compression ratio as described above, there is a problem that a reduction in thermal efficiency occurs due to the low compression ratio.

On the other hand, the fuel gas diffusion combustion system and the fuel oil diffusion combustion system have no fear of abnormal combustion, and therefore, the compression ratio can be increased to a level parallel to that of a normal diesel engine, and there is no output limitation. However, when the fuel operation is performed by the DF internal combustion engine with the compression ratio increased as described above, the NOx emission amount increases without decreasing the thermal efficiency, and therefore, in the exhaust gas restriction strengthening area, there is a problem that an additional device such as EGR or SCR must be added to the internal combustion engine.

Disclosure of Invention

An object of the present invention is to provide a control device for an internal combustion engine, a ship including the control device, and an operation method for the internal combustion engine, which can suppress the discharge of NOx without using an additional device in an exhaust gas restriction strengthening sea area, and can secure the output of the internal combustion engine in another sea area.

(1) In order to achieve the above object, a control device for an internal combustion engine according to the present invention includes:

a combustion mode selection means capable of selecting at least a fuel gas diffusion combustion mode and a fuel gas premix combustion mode during operation of the internal combustion engine; a fuel injection control unit that controls fuel injection so that the fuel injection is in a fuel injection mode corresponding to the combustion method selected by the combustion method selection unit; and an actual compression ratio control means for controlling an actual compression ratio so that the actual compression ratio becomes an actual compression ratio corresponding to the combustion method selected by the combustion method selection means, wherein the actual compression ratio control means controls the actual compression ratio to a low compression ratio when the fuel gas premixed combustion method is selected, and controls the actual compression ratio to a high compression ratio when the fuel gas diffusion combustion method is selected.

(2) Preferably, the fuel gas premixed combustion system includes: a fuel gas-all-premixed combustion system in which fuel gas is used and fuel gas is combusted only by a fuel gas-premixed combustion system; and a fuel gas partially premixed combustion mode in which a part of the fuel gas is premixed combusted and the remaining fuel gas is diffusion combusted, wherein the combustion mode selection means is capable of selecting at least the fuel gas diffusion combustion mode, the fuel gas all-premixed combustion mode, and the fuel gas partially premixed combustion mode during operation of the internal combustion engine, and the actual compression ratio control means controls the actual compression ratio to a low compression ratio if the fuel gas all-premixed combustion mode or the fuel gas partially premixed combustion mode is selected, and controls the actual compression ratio to a high compression ratio if the fuel gas diffusion combustion mode is selected.

(3) Preferably, the internal combustion engine includes a valve train device capable of changing an exhaust valve closing timing, the actual compression ratio control means controls the actual compression ratio by operating the exhaust valve closing timing, the actual compression ratio control means controls the exhaust valve closing timing to a retarded angle side when the actual compression ratio is controlled to a low compression ratio, and controls the exhaust valve closing timing to an advanced angle side when the actual compression ratio is controlled to a high compression ratio.

(4) Preferably, the internal combustion engine includes a supercharger capable of increasing and decreasing a supercharging amount, and a supercharging control means for setting the supercharging amount to a normal state when the combustion method selection means selects the fuel gas diffusion combustion method, and setting the supercharging amount to an increased state when the combustion method selection means selects the fuel gas premix combustion method, at least in a high load state in which a load of the internal combustion engine is larger than a constant load.

(5) In this case, it is preferable that the supercharger be a supercharger capable of switching between two-stage supercharging and single-stage supercharging,

the supercharging control means sets the supercharger to a single-stage supercharging when the supercharging amount is set to a normal state, and sets the supercharger to a two-stage supercharging when the supercharging amount is set to an increased state.

(6) Further, it is preferable that the supercharging control means sets the supercharging amount to an increased state when the load of the internal combustion engine is in a low load state equal to or less than the constant load in the case where the combustion mode selection means selects the fuel gas diffusion combustion mode.

(7) Preferably, the control device for an internal combustion engine includes a determination unit configured to determine whether or not an exhaust gas restriction state in which exhaust gas of the internal combustion engine is to be restricted is present, wherein the combustion mode selection unit selects the fuel gas premix combustion mode when the determination unit determines that the exhaust gas restriction state is present, and the combustion mode selection unit selects the fuel gas diffusion combustion mode when the determination unit determines that the exhaust gas restriction state is not present.

(8) Preferably, the internal combustion engine is a marine internal combustion engine provided in a ship, and the determination unit determines that the exhaust gas restriction state is established when a navigation sea area in which the ship is navigating is within an exhaust gas restriction sea area, and determines that the exhaust gas restriction state is not established when the navigation sea area is outside the exhaust gas restriction sea area.

(9) A ship according to the present invention is characterized by comprising the control device for an internal combustion engine according to any one of (1) to (8) above and the internal combustion engine controlled by the control device.

(10) The method for operating an internal combustion engine according to the present invention includes: a combustion method selection step of selecting one of combustion methods including at least a fuel gas diffusion combustion method and a fuel gas premixed combustion method during operation of the internal combustion engine, and a compression ratio control step; in the compression ratio control step, the actual compression ratio of the internal combustion engine is controlled in accordance with the combustion method selected in the combustion method selection step.

(11) Preferably, the fuel gas premixed combustion system includes: a fuel gas-all-premixed combustion system in which fuel gas is used and fuel gas is combusted only by a fuel gas-premixed combustion system; and a combustion mode selection step of selecting one of combustion modes including at least the fuel gas diffusion combustion mode, the fuel gas all-premixed combustion mode, and the fuel gas partial-premixed combustion mode during operation of the internal combustion engine.

Effects of the invention

According to the present invention, the fuel injection control means controls the fuel injection so that the fuel injection is in the fuel injection mode corresponding to the selected combustion mode, and the actual compression ratio control means controls the actual compression ratio so that the actual compression ratio is in the actual compression ratio corresponding to the selected combustion mode, and particularly, if the fuel gas premixed combustion mode is selected, the actual compression ratio control means controls the actual compression ratio to a low compression ratio, and if the fuel gas diffusion combustion mode is selected, the actual compression ratio control means controls the actual compression ratio to a high compression ratio, so that the fuel gas premixed combustion mode with a small NOx emission amount can be stably executed. Thus, for example, in the exhaust gas restriction strengthening sea area, the marine internal combustion engine can select the fuel gas premix combustion method and suppress the discharge of NOx without using an additional device, and in the other sea area, the marine internal combustion engine can select the fuel gas diffusion combustion method and secure the output of the internal combustion engine.

Further, the fuel gas premixed combustion system of the internal combustion engine includes: a fuel gas premixed combustion system in which fuel gas is used and the fuel gas is premixed and combusted; and a fuel gas partially premixed combustion method of premixed combusting a part of the fuel gas and diffusion combusting the remaining fuel gas, the actual compression ratio control means controls the actual compression ratio to a low compression ratio when the fuel gas fully premixed combustion method or the fuel gas partially premixed combustion method is selected, and controls the actual compression ratio to a high compression ratio when the fuel gas diffusion combustion method is selected, so that the fuel gas fully premixed combustion method or the fuel gas partially premixed combustion method with a small NOx emission amount can be stably executed. Thus, for example, in the exhaust gas restriction strengthening sea area, the marine internal combustion engine can select the fuel gas all-premixed combustion method or the fuel gas partial-premixed combustion method, suppress the discharge of NOx without using an additional device, and in the other sea area, can select the fuel gas diffusion combustion method to secure the output of the internal combustion engine.

Drawings

Fig. 1 is a block diagram showing a control device for an internal combustion engine according to a first embodiment of the present invention.

Fig. 2 is an overall configuration diagram of an internal combustion engine according to a first embodiment of the present invention.

Fig. 3A and 3B are schematic views of the structure of the cylinder inner periphery including the cylinder liner of fig. 2, fig. 3A being a plan view, and fig. 3B being a longitudinal sectional view. Fig. 3A and 3B show a state where fuel gas is injected in a premixed fuel system.

Fig. 4 is a timing chart for explaining control by the control device for the internal combustion engine according to the first embodiment of the present invention.

Fig. 5 is a block diagram showing a control device for an internal combustion engine according to a second embodiment of the present invention.

Detailed Description

Embodiments according to the present invention will be described below with reference to the drawings.

The embodiments described below are merely examples, and are not intended to exclude the application of various modifications and techniques that are not explicitly described in the embodiments below. The configurations of the following embodiments can be variously modified within a range not departing from the gist thereof, and can be selected and selected as necessary, or can be appropriately combined.

[ first embodiment ]

[ Structure of internal Combustion Engine ]

A first embodiment of the present invention will be explained. 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 fig. 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 internal combustion engine) 1. The internal combustion engine 1 employs a low-speed two-stroke one-cycle uniflow scavenging system used as a marine main engine of a liquefied gas carrier such as an LNG carrier. The internal combustion engine 1 is configured as a dual-fuel internal combustion engine (hereinafter, also referred to as a DF internal combustion engine) that can use fuel gas in addition to fuel oil.

The internal combustion engine 1 includes a lower platen 3, a frame 5 provided on the platen 3, and a jacket 7 provided on the frame 5. The platen 3, the frame 5, and the jacket 7 are fastened and fixed integrally by a plurality of tie bolts (not shown) extending in the vertical direction.

The jacket 7 is provided with a cylinder liner 9, and a plurality of scavenging ports 10 are formed in the lower end side of the cylinder liner 9. A cylinder head 11 is provided at the upper end of the cylinder liner 9. The cylinder head 11 is provided with an exhaust valve 12. Thus, the following direct-flow scavenging method is adopted: air is introduced as scavenging gas into the cylinder from below through a scavenging port 10 provided at the lower end side of the cylinder liner 9, and combustion exhaust gas is discharged from an exhaust valve 12 located above the cylinder.

The exhaust gas discharged from the exhaust valve 12 is sent to the supercharger 16 after being collected to the exhaust manifold 14. In the supercharger 16, an exhaust turbine (not shown in fig. 2) is rotated by the introduced exhaust gas, and thereby a compressor (not shown in fig. 2) coaxially connected is rotated. The compressor compresses air introduced from the outside, and is introduced to the scavenging manifold 20 after being cooled by the air cooler 18. The compressed air introduced to the scavenging manifold 20 is introduced to the scavenging port 10. The details of the supercharger 16 will be described later.

A piston 13 capable of reciprocating is provided in a space formed by the cylinder liner 9 and the cylinder head 11. At the lower end of the piston 13, the upper end of a piston rod 15 is rotatably mounted. In the diesel engine 1 of the present embodiment, the super-long stroke is set such that the ratio of the stroke of the piston 13 to the inner diameter of the cylinder liner 9, that is, the bore stroke ratio is 3 or more.

The platen 3 is configured as a crankcase, and is provided with a crankshaft 17. The rotational output from the crankshaft 17 is transmitted to a propeller for propelling the ship. The lower end of the connecting rod 19 is rotatably connected to the upper end of the crankshaft 17.

The frame 5 is provided with a crosshead 21 which rotatably connects 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. A pair of slide plates 23 extending in the vertical direction are provided on both sides (left and right in fig. 2) of the crosshead 21 in a state of being fixed to the frame 5 side.

Fig. 3A and 3B schematically show the structure of the inner periphery of the cylinder of the diesel engine 1. As shown in these figures, the cylinder head 11 is provided with a fuel gas injection valve for premixing (hereinafter referred to as "premixed gas valve") 30 as a first fuel gas injection valve, a fuel gas injection valve for diffusion (hereinafter referred to as "diffused gas valve") 32 as a second fuel gas injection valve, and a fuel injection valve (hereinafter referred to as "fuel valve") 34.

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

The gas injection pressure from the premixed gas valve 30 is, for example, 1.0MPa to 50MPa in absolute pressure, and preferably 20MPa to 30MPa in absolute pressure. The nozzle provided at the tip end of the premixed gas valve 30 is provided with a plurality of injection holes, and the fuel gas is injected into the cylinder from each injection hole. For example, in the example shown in fig. 3B, the fuel gas is injected from each of the four injection holes. As shown in the drawing, the direction of the fuel gas injected from the premixed gas valve 30 is set to be the direction of the piston 13, more specifically, the direction of the fuel gas injected toward the top face of the piston 13, which is configured to be circular, at the top of the piston 13 after the scavenging port 10 is closed by the piston 13.

The premixed gas valve 30 may be provided with each injection hole so that the fuel gas is injected from at least one injection hole in the direction of the piston 13, and it is not necessary to provide all the injection holes to inject the fuel gas in the direction of the piston 13.

The premixed gas valve 30 is started when the diesel engine 1 is operated by premixed combustion by fuel gas (fuel gas premixed combustion), and is stopped without being started when the diesel engine is operated by diffusion combustion by fuel gas (fuel gas diffusion combustion operation) or diffusion combustion by fuel oil (fuel oil diffusion combustion operation). The premixed gas valve 30 is started and stopped based on a command from a control device 40 described later.

The injection timing of the premixed gas valve 30 is controlled by a control device 40 described later, and is set to a range in which the fuel gas does not leak from the exhaust valve 12 to the outside of the system, specifically, 140 or more and 20degBTDC or less (BTDC: Before Beforep Dead center), and preferably 100 or more and 60degBTDC or less, for example. Here, the timing at which the exhaust valve 12 is closed is, for example, about 90 degBTDC.

The period during which the fuel gas is injected (i.e., the period during which the fuel gas is continuously injected) is, for example, 20deg to 30deg when the load of the diesel engine 1 is 100%.

As shown in fig. 3A, two diffusion gas valves 32 are provided on the outer peripheral side of the cylinder head 11 when the cylinder head 11 is viewed in plan. The two diffusion gas valves 32 are disposed at positions facing each other across the center of the cylinder head 11 (i.e., the center of the exhaust valve 12). In the present embodiment, each diffusion gas valve 32 is disposed at a position circumferentially offset from the premixed gas valve 30 by a predetermined angle, but the diffusion gas valve 32 and the premixed gas valve 30 may be disposed on the cylinder head 11. The number of the diffusion gas valves 32 is only two as an example, but may be one or three or more, and is the same as the number of the fuel valves 34.

The diffusion gas valve 32 is connected to a fuel gas supply source, not shown, and injects fuel gas into a cylinder formed by the cylinder liner 9 and the cylinder head 11. As the fuel gas, a hydrocarbon gas such as vaporized LNG is used as in the case of the premixed gas valve 30.

The gas injection pressure from the diffusion gas valve 32 is higher than the pressure of the air (scavenging gas) compressed by the piston 13, and is set to 50MPa or less, for example, 10MPa or more and 30MPa or less in absolute pressure. A nozzle provided at the tip of the diffusion gas valve 32 is provided with a plurality of injection holes, 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 set to be a horizontal direction or a direction slightly downward from the horizontal direction, and is set to be a direction not toward the top of the piston 13 so that the piston 13 is raised near the top dead center and diffusion combustion is performed based on the fuel gas in the narrowed combustion space.

The diffusion gas valve 32 is activated when the diesel engine 1 is operated by diffusion combustion, and is not activated and stopped when the premixed combustion operation by the fuel gas or the diffusion combustion operation by the fuel oil is performed. The activation and deactivation of the diffusion gas valve 32 is performed based on a command from a control device 40 described later.

The period during which the diffusion gas valve 32 injects the fuel gas (i.e., the period during which the fuel gas is continuously injected) is controlled by a control unit (not shown), and is set to 20deg to 30deg when the load of the diesel engine 1 is 100%, for example.

As shown in fig. 3A, when the cylinder head 11 is viewed in plan, two fuel valves 34 are provided on the outer peripheral side of the exhaust valve 12 and on the inner peripheral sides of the premixed gas valve 30 and the diffusion gas valve 32. The two fuel valves 34 are disposed at positions facing each other across the center of the cylinder head 11 (i.e., the center of the exhaust valve 12). However, each fuel valve 34 is disposed at a position circumferentially offset by a predetermined angle from the diffusion gas valve 32 and the premixed gas valve 30. The number of the fuel valves 34 is only two for illustration, but may be one or three or more. Further, the exhaust valve 12 may not be provided on the inner circumferential side of the premixed gas valve 30 and the diffusion gas valve 32 as long as it is on the outer circumferential side.

The fuel valve 34 is connected to a fuel supply source, not shown, and injects fuel into a cylinder formed by the cylinder liner 9 and the cylinder head 11. As the fuel oil, for example, heavy oil having a high proportion of residual oil such as C heavy oil (heavy oil of which 90% or more is residual oil) mentioned in JIS standard of japan is used.

The injection pressure from the fuel valve 34 is higher than the pressure of the air (scavenging air) compressed by the piston 13, and is set to, for example, 30MPa to 80MPa in absolute pressure. A nozzle provided at the tip end of the fuel valve 34 is provided with a plurality of nozzle holes, and fuel is injected into the cylinder from each nozzle hole. For example, the direction of the fuel injected from the fuel valve 34 is set to be a horizontal direction or a direction slightly downward from the horizontal direction, and is set to be a direction not toward the top of the piston 13 so that the piston 13 is raised near the top dead center and ignition or diffusion combustion is performed in the narrowed combustion space.

When the diesel engine 1 is operated by diffusion combustion of fuel, the fuel valve 34 is operated to inject fuel for diffusion combustion (so-called fuel-only combustion operation), and the fuel valve 34 is operated to inject pilot oil for ignition in the premixed combustion operation by fuel gas and the diffusion combustion operation by fuel gas. The fuel valve 34 is operated based on a command from a control unit not shown.

[ as the operation mode of the dual-fuel internal combustion engine ]

Next, the operation mode of the diesel engine 1 configured as described above will be described. The internal combustion engine 1 is operated by appropriately switching between a fuel gas operation in which three combustion modes, i.e., a fuel gas diffusion combustion mode, a fuel gas all-premixed combustion mode, and a fuel gas partial-premixed combustion mode, are selectively used, and a fuel oil operation in which a fuel oil diffusion combustion mode is used.

The dual-fuel internal combustion engine has the following action modes: the fuel cell system is characterized by comprising a total premixed fuel gas mode in which a fuel gas total premixed combustion method is performed using a fuel gas to perform premixed combustion, a diffusion fuel gas mode in which a fuel gas is used to perform diffusion combustion using a fuel gas, a partial premixed fuel gas mode in which a fuel gas is used to perform partial premixed combustion using a fuel gas and the remaining fuel gas is used to perform diffusion combustion, and a diffusion fuel mode (so-called fuel only combustion mode) in which fuel oil is used to perform diffusion combustion. In addition, when it is impossible to distinguish whether the diffusion combustion or the diffusion combustion method is the fuel gas diffusion combustion or the fuel diffusion combustion, the diffusion combustion or the diffusion combustion method is simply referred to as the diffusion combustion or the diffusion combustion method. The fuel gas premix combustion system is a combustion system using at least the premix gas valve 30 as fuel supply, and includes a fuel gas all-premix combustion system and a fuel gas partial premix combustion system. That is, the fuel gas premix combustion system broadly means a combustion system in which combustion is performed by a premix combustion system using a fuel gas, and means either one or both of a full premix combustion system and a partial premix combustion system of a fuel gas.

In the all-premixed fuel gas mode, the premixed gas valve 30 is used as a fuel supply and the fuel valve 34 is used as a pilot.

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

In the partially premixed fuel gas mode, the premixed gas valve 30 is used as a fuel supply and the fuel valve 34 is used as a pilot for the combustion of the fuel gas premixed combustion method, and the diffusion gas valve 32 is used as a fuel supply and the fuel valve 34 is used as a pilot for the combustion of the fuel gas diffusion combustion method.

In the diffusion fuel mode, the fuel valve 34 is primarily used.

In the all premixed fuel gas mode, since the NOx emission amount is small, it is preferable when the ship is sailing in an ECA (sea area for air pollutant emission control, also simply referred to as an exhaust gas control sea area), for example. However, abnormal combustion such as pre-ignition and knocking is likely to occur in the all-premixed fuel gas mode, and in order to avoid these problems, it is necessary to lower the compression ratio as compared with the case of the normal (diffusion combustion system). When the compression ratio is lowered, the maximum output is limited.

The diffusion fuel gas mode has higher combustion stability than the premixed fuel gas mode, and therefore can employ a higher compression ratio, but on the other hand, the diffusion fuel gas mode has a larger amount of NOx generation than the premixed fuel gas mode, and therefore is used, for example, when a ship is sailing outside the ECA. However, since the SOx generation amount in the diffusion fuel gas mode is as small as in the diffusion fuel mode, the mode can be used in place of the premixed fuel gas mode when combustion stability is required even in the ECA within a range not exceeding the NOx limit amount and within a predetermined time.

The diffusion fuel mode can employ a high compression ratio due to higher combustion stability, but SOx from the fuel is generated more than in the case of using fuel gas. Therefore, for example, when navigating in a sea area where the SOx release restriction is relatively moderate, the diffusion fuel mode is used in a case where higher combustion stability is required and a case where fuel is better than fuel gas.

(all premixed fuel gas mode)

The overall premixed fuel gas mode will be explained.

As shown in fig. 3A and 3B, in the initial stage of the compression stroke after the exhaust valve 12 is closed and the scavenging port 10 is closed by the piston 13, the high-pressure fuel gas having an absolute pressure of 1.0MPa to 50MPa, preferably 20MPa to 30MPa, is injected from the premixed gas valve 30 toward the top of the piston 13 by a command from the control unit. In the all-premixed fuel gas mode, the diffusion gas valve 32 is closed, and the fuel gas is mainly injected from the premixed gas valve 30. However, the diffusion gas valve 32 may be used in combination.

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

Since the premixed gas valve 30 is injected from the upper cylinder head 11 toward the top of the lower piston 13, the fuel gas can be injected as a whole by effectively utilizing the longitudinal direction of the combustion space formed vertically after the scavenging port 10 is closed by the piston 13, and the mixing of the fuel gas and the air (scavenging gas; oxidizing gas) can be promoted. In particular, since the diesel engine 1 of the present embodiment is configured to have an ultra-long stroke, mixing by fuel gas injection in the longitudinal direction is more effective.

After the premixed gas is formed in the cylinder by the fuel gas injected from the premixed gas valve 30, the piston 13 moves upward to compress the premixed gas. Then, when the vicinity of the top dead center is reached, pilot oil is injected from the fuel valve 34 and ignition is performed. The flame formed by this ignition propagates through the premixed gas, generally performs premixed combustion, performs combustion and an expansion stroke (at this time, injection of pilot oil from the fuel valve 34 is stopped), and the piston 13 moves downward.

(diffusion Fuel gas mode)

The diffusion fuel gas mode will be explained.

In the compression stroke after the exhaust valve 12 closes and the scavenging port 10 is closed by the piston 13, only the air introduced from the scavenging port 10 is compressed. Then, when the piston 13 reaches the vicinity of the top dead center, fuel is injected from the fuel valve 34 as pilot oil, and simultaneously with or immediately after the pilot oil, high-pressure gaseous fuel is injected from the diffusion gas valve 32 at a cylinder internal pressure at the time of compression of 50MPa (absolute pressure) or more, and more preferably at a high pressure of 10MPa or more and 30MPa or less in absolute pressure. As a result, diffusion combustion is performed in the cylinder by the injection of the fuel gas (at this time, the injection of the pilot oil from the fuel valve 34 is stopped), and the piston 13 is pushed downward by the expansion stroke.

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

(partially premixed fuel gas mode)

The partially premixed fuel gas mode will be explained.

In the partially 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 in the fully premixed 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 in the diffusion fuel gas mode. At this time, the premixed gas valve 30 is closed.

(diffusion Fuel mode)

The diffusion fuel mode (i.e., fuel only combustion mode) is not illustrated, but is similar to diffusion combustion using a general fuel. Specifically, the exhaust valve 12 is closed to compress air while the piston 13 is moving upward, fuel is injected from the fuel valve 34 at a high pressure near the top dead center to perform diffusion combustion, and the piston 13 is moved downward by an expansion stroke based on the diffusion combustion.

By providing the diffusion fuel mode in this manner, the diesel engine 1 can be established as a dual fuel engine (DF engine) that operates by using a fuel gas in combination.

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

(premix transition control)

The internal combustion engine 1 of the present embodiment is further provided with a premix transition control that is performed when transitioning from the diffusion fuel gas mode or the diffusion fuel mode to the all-premixed fuel gas mode or the partially premixed fuel gas mode.

When switching from the diffusion fuel gas mode using fuel gas to the all-premixed fuel gas mode or the partially premixed fuel gas mode, the fuel gas injected from the diffusion gas injection valve 32 is decreased, and the fuel gas injected from the premixed gas valve 30 is increased. That is, when switching from the diffusion fuel gas mode to the premixed fuel gas mode, the premix ratio, which is the ratio of the fuel gas injected from the premix gas valve 30, to the total fuel gas injected, gradually increases from 0% (diffusion fuel gas mode in which only the fuel gas is diffusion-combusted) to a predetermined ratio (100% in the case of the total premixed fuel gas mode in which only the premixed combustion is performed, and a predetermined ratio set in the case of the partial premixed fuel gas mode in which the premixed combustion and the diffusion combustion are used in combination). At this time, by the premix transition control by the control unit, in the combustion stroke in the first cycle immediately after the switching from the diffusion fuel gas mode to the premix fuel gas mode, the amount of fuel gas injected from the premix gas valve 30 is increased to a concentration at which the fuel gas injected from the premix gas valve 30 is completely combusted, and the premix ratio is continuously increased. Specifically, in the first cycle of the mode switching, the premixing ratio is continuously increased from 0% to 40% to 60%. Then, after the premix ratio becomes 40% or more and 60% or less in the first cycle immediately after the mode switching, the premix ratio is gradually increased toward a predetermined ratio in a plurality of subsequent cycles.

Thus, when switching from the diffusion fuel gas mode to the premixed fuel gas mode, the premixed fuel is completely combusted from the first cycle, and thereby, the discharge of unburned gas from the exhaust valve 12 can be prevented. That is, by gradually increasing the premix ratio from 0% through a plurality of cycles immediately after the mode switching, it is possible to avoid a problem that the amount of fuel gas injected from the premix gas valve 30 is small and the premix concentration is too low to completely combust the fuel gas in an initial cycle in which the premix ratio is small, and that Hydrocarbons (HC) which are unburned fuel gas are discharged from the exhaust valve 12.

The same control is also performed when switching from the diffusion fuel mode using fuel to the premixed fuel gas mode. That is, when switching from the diffusion fuel mode to the mixed fuel gas mode, the fuel injected from the fuel valve 34 is decreased, and the fuel gas injected from the premixed gas valve 30 is increased. That is, when switching from the diffusion fuel mode to the premixed fuel gas mode, the premixed ratio, which is the ratio of the amount of heat generated by the fuel gas injected from the premixed gas valve 30, in the entire fuel injected, is gradually increased from 0% (diffusion fuel mode in which only fuel is diffusion-combusted) toward a predetermined ratio (100% in the case of the premixed fuel gas mode in which only premixed combustion is performed, and a predetermined ratio set in the case of the partially premixed fuel gas mode in which premixed combustion and diffusion combustion are combined). At this time, in the combustion stroke in the first cycle immediately after the switching from the diffusion fuel mode to the premixed fuel gas mode, the premixing transition control by the control section increases the amount of the fuel gas injected from the premixed gas valve 30 to increase the premixing ratio until the concentration at which the fuel gas injected from the premixed gas valve 30 is completely combusted is reached. Specifically, in the first cycle of the mode switching, the premixing ratio is continuously increased from 0% to 40% to 60%. Then, after the premix ratio becomes 40% or more and 60% or less in the first cycle immediately after the mode switching, the premix ratio is gradually increased in a plurality of subsequent cycles.

Thus, when switching from the diffusion fuel mode to the premixed fuel gas mode, the premixed fuel is completely combusted from the first cycle, and thereby, the discharge of unburned gas from the exhaust valve 12 can be prevented. That is, if the premix ratio is gradually increased from 0% through a plurality of cycles immediately after the mode is switched, it is possible to avoid a problem that the amount of fuel gas injected from the premix gas valve 30 is small and the premix concentration is too low to completely combust the fuel gas in an initial cycle in which the premix ratio is small, and that Hydrocarbons (HC) which are unburned fuel gas are discharged from the exhaust valve 12.

[ control of control device based on Dual Fuel internal Combustion Engine ]

Here, the control of the control device 40 for a dual-fuel internal combustion engine according to the present embodiment will be described with reference to fig. 1.

As shown in FIG. 1, the control device 40 includes a determination unit (determination means) 42 and an operation mode selection unit (combustion mode selection means) 44 as functional elements, a fuel injection control unit (fuel injection control means) 46, an actual compression ratio control unit (actual compression ratio control means) 48, and a supercharging pressure control unit (supercharging pressure control means) 50, the determination unit 42 determines whether or not the internal combustion engine 1 is in an exhaust gas restriction state in which exhaust gas should be restricted, the operation mode selection unit 44 appropriately selects and sets an operation mode (combustion mode) during operation of the internal combustion engine 1, the fuel injection control unit 46 controls fuel injection to a fuel injection mode corresponding to the operation mode selected and set, the actual compression ratio control unit 48 controls the actual compression ratio to an actual compression ratio corresponding to the operation mode selected and set, and the supercharging pressure control unit 50 controls the supercharging pressure of the supercharger 16.

First, the determination by the determination unit 42 will be described. The determination unit 42 determines whether or not the sea area in which the ship equipped with the internal combustion engine 1 is sailing is an exhaust gas control sea area, and determines that the internal combustion engine 1 is in a state in which exhaust gas should be controlled if the sailing sea area is the exhaust gas control sea area, and the determination of the sailing sea area can be performed based on the position information of the ship obtained from, for example, a GPS or the like and the information of the exhaust gas control sea area stored in advance.

When the determination unit 42 determines that the marine vessel's navigation sea area is the exhaust gas restriction sea area (the internal combustion engine 1 is in the exhaust gas restriction state), the operation mode selection unit 44 selects the all-premixed fuel gas mode or the part-premixed fuel gas mode, and when the determination unit 42 determines that the marine vessel's navigation sea area is not the exhaust gas restriction sea area (the internal combustion engine 1 is not in the exhaust gas restriction state), the operation mode selection unit 44 selects the diffusion fuel oil mode or the diffusion fuel gas mode.

The fuel injection control unit 46 controls the fuel injection to a fuel injection mode corresponding to the operation mode set by the operation mode selection unit 44. That is, when the all-premixed fuel gas mode is set, as described above, the premixed gas valve 30 is used for fuel supply and the fuel valve 34 is used for pilot for fuel injection. When the partial premix fuel gas mode is set, fuel injection is performed using the premix gas valve 30 and the diffusion gas valve 32 for fuel supply and the fuel valve 34 for pilot, as described above. When the diffusion fuel gas mode is set, fuel injection is performed using the diffusion gas valve 32 for fuel supply and the fuel valve 34 for pilot, as described above. When the diffusion fuel mode is set, fuel injection is performed using the fuel valve 34 as described above.

The actual compression ratio control portion 48 controls the actual compression ratio to correspond to the operation mode set by the operation mode selection portion 44. That is, when the all-premixed fuel gas mode or the partial premixed fuel gas mode is set, the actual compression ratio is controlled to the low compression ratio, and when the diffusion fuel gas mode or the diffusion fuel mode is set, the actual compression ratio is controlled to the high compression ratio.

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

As described above, in the all-premixed fuel gas mode or the partially premixed fuel gas mode, the premixed gas valve 30 is used to inject the fuel gas toward the piston 13 (for example, from the upper side toward the lower side) after the scavenging port 10 is closed by the piston 13, whereby the fuel gas can be injected as a whole by effectively utilizing the piston reciprocating direction (for example, the vertical direction) of the combustion space after the scavenging port 10 is closed by the piston 13, and the mixing of the fuel gas and the oxidizing gas can be promoted.

Therefore, the local minimum λ (λ is an air excess ratio) at which the local fuel gas concentration becomes high can be increased, and abnormal combustion such as preignition and knocking can be avoided as much as possible, thereby improving the combustion stability. Further, since abnormal combustion such as preignition and knocking can be avoided as much as possible, the amount of decrease in the compression ratio can be reduced as compared with a conventional premixed internal combustion engine, the decrease in the thermal efficiency can be minimized, and the engine can be operated under a high load with a high Pme (in-cylinder mean effective pressure).

However, even if the amount of decrease in the compression ratio can be made smaller than in the conventional premix engine, in the diffusion fuel mode or the diffusion fuel gas mode, the compression ratio that can be used in the all-premix fuel gas mode or the partial premix fuel gas mode is not sufficient to increase the thermal efficiency of the engine 1 and obtain a large output, and a higher compression ratio must be used.

Therefore, the internal combustion engine 1 is configured to be able to change the actual compression ratio during operation of the internal combustion engine 1.

In the present embodiment, the actual compression ratio is changed by changing the closing timing of the exhaust valve 12. That is, by delaying the closing timing of the exhaust valve 12 (i.e., by a delay angle), the cylinder internal volume at the time of substantial start of compression of the internal combustion engine 1 becomes small, and the actual compression ratio can be made small. Conversely, by advancing the closing timing of the exhaust valve 12 (i.e., advancing the closing timing), the cylinder internal volume at the time of substantial start of compression of the internal combustion engine 1 becomes large, and the actual compression ratio can be increased.

Therefore, the internal combustion engine 1 includes a valve gear (variable valve gear) 12A capable of changing at least the closing timing of the exhaust valve 12. The valve operating system 12A is a so-called camless valve operating system in which the exhaust valve 12 is controlled by an actuator (not shown), and the valve operating system 12A can easily change the closing timing of the exhaust valve 12 by controlling the operation of the actuator by the control device 40. However, the variable valve gear may be a device using a mechanical variable valve mechanism of the internal combustion engine 1.

The supercharging pressure control unit 50 controls the supercharging pressure amount in accordance with the operation mode set by the operation mode selection unit 44. That is, at least in the case of a high load state in which the load of the internal combustion engine 1 is greater than a certain load, the amount of pressure increase is set to the normal state when the diffusion fuel gas mode or the diffusion fuel mode is set, and the amount of pressure increase is set to the increased state when the all-premixed fuel gas mode or the partial premixed fuel gas mode is set.

As described above, this causes the amount of air trapped in the cylinder to decrease and the maximum output of the internal combustion engine 1 to be limited when the actual compression ratio is decreased by changing the closing timing of the exhaust valve 12 when the all-premixed fuel gas mode or the partially premixed fuel gas mode is set, and therefore, in the present embodiment, the amount of air trapped in the cylinder is increased by increasing the supercharging amount of the supercharger 16, and the maximum output of the internal combustion engine 1 can be improved.

Fig. 4 is a timing chart illustrating a change in the closing timing of the exhaust valve 12, and shows the opening/closing timing of the scavenging port 10, the opening/closing timing of the exhaust valve 12, and the cylinder internal pressure corresponding thereto together with the timing of fuel injection. As shown in fig. 4, the cylinder internal pressure decreases as the piston 13 moves from the top dead center TDC to the bottom dead center BDC, and further decreases when the exhaust valve 12 opens at time t1, but thereafter, the cylinder internal pressure slightly recovers when the scavenging port 10 opens at time t2, and the piston 13 approaches the bottom dead center BDC. After the scavenging port 10 is closed at a time point t3 and thereafter the exhaust valve 12 is closed at a time point t4, the cylinder internal pressure increases as the piston 13 moves toward the top dead center TDC.

The opening/closing timing of the exhaust valve 12 is shown by the solid line in the normal state, and the actual compression ratio can be lowered when the closing timing of the exhaust valve 12 is delayed from time t4 to time t 5. At the same time, however, the degree of the cylinder internal pressure from the normal closing timing shown by the solid line (diffusion combustion) decreases as shown by the two-dot chain line (premixed combustion 2). Thus, the amount of air trapped in the cylinder is reduced. On the other hand, by increasing the supercharging amount of the supercharger 16, the amount of air trapped in the cylinder increases, and as a result, the cylinder internal pressure recovers as shown by the broken line (premixed combustion 1).

The control of the supercharging amount of the supercharger 16 by the supercharging pressure control unit 50 will be specifically described.

In the present embodiment, the supercharger 16 provided in the internal combustion engine 1 is configured such that two

superchargers

16A and 16B are connected in a linear arrangement and two-stage supercharging and one-stage supercharging are switched by switching valves.

That is, a scavenging connection passage 161a is provided between the compressor 16AC of the first supercharger 16A on the upstream side of the scavenging passage and on the downstream side of the exhaust passage and the compressor 16BC of the second supercharger 16B on the downstream side of the scavenging passage and on the upstream side of the exhaust passage, and an exhaust connection passage 162a is provided between the exhaust turbine 16AT of the first supercharger 16A and the exhaust turbine 16BT of the second supercharger 16B. Further, a scavenging connection passage 161b is provided between the compressor 16AC of the first supercharger 16A and the scavenging manifold 20 (see fig. 2), and an exhaust connection passage 162b is provided between the exhaust turbine 16AT of the first supercharger 16A and the exhaust manifold 14 (see fig. 2). Further, a scavenging connection passage 161c is provided between the compressor 16BC of the second supercharger 16B and the scavenging manifold 20, and an exhaust connection passage 162c is provided between the exhaust turbine 16BT of the second supercharger 16B and the exhaust manifold 14.

Further, an air cooler 18 is provided in each of the scavenging

connection passages

161b and 161 c. The air cooler 18 of the scavenging

connection passages

161b and 161c can also be used.

Opening/closing valves 163a to 163c are inserted into the scavenging connection passages 161a to 161c, and opening/closing valves 164a to 164c are inserted into the exhaust connection passages 163a to 163 c.

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 internal combustion engine 1 is discharged from the exhaust manifold 14 through the exhaust turbine 16BT of the second supercharger 16B and the exhaust turbine 16AT of the first supercharger 16A, and the exhaust turbines 16BT and 16AT are rotationally driven. Thereby, the compressors 16AC, 16BC are rotationally driven and pressurize the scavenging air by two-stage supercharging.

When the open/

close valves

163a, 163c, 164a, 164c are closed, the open/

close valves

163b, 164b are opened, and the exhaust gas discharged from the internal combustion engine 1 is discharged from the exhaust manifold 14 through the exhaust turbine 16AT of the first supercharger 16A, while the exhaust turbine 16AT is rotationally driven. Thereby, the compressor 16AC is rotationally driven, and the scavenging air is pressurized by single-stage supercharging.

In this way, when the all-premixed fuel gas mode or the partially premixed fuel gas mode is set, the actual compression ratio is reduced by changing the closing timing of the exhaust valve 12 to suppress abnormal combustion such as pre-ignition and knocking, and thereby the reduction in the amount of air trapped in the cylinder is compensated for by the increase in the supercharging pressure by the two-stage supercharging, and the improvement in the maximum output of the internal combustion engine 1 can be achieved.

Further, in the supercharging control portion 50, when the diffusion fuel gas mode or the diffusion fuel mode is set, the supercharging amount is set to the normal state by the single-stage supercharging when the load of the internal combustion engine 1 is in the high load state, but this is because it is difficult to increase the supercharging amount by the two-stage supercharging when the load of the internal combustion engine 1 is in the low load state equal to or less than a certain load, the supercharging amount can be expected to be increased by the two-stage supercharging, and therefore the two-stage supercharging is executed.

The control device for a dual-fuel internal combustion engine according to the first embodiment of the present invention and the ship including the control device are configured as described above, and therefore, when the ship enters the exhaust gas restriction sea area, the entire premixed fuel gas mode or the partially premixed fuel gas mode can be selected, and the ship can be operated in a state where the exhaust gas restriction is released in a state where the NOx emission amount is small. Further, when the ship is out of the exhaust gas limited sea area, the diffusion fuel gas mode or the diffusion fuel mode can be selected, and the ship can be operated in a state where a large maximum output is efficiently obtained.

In the present control device, particularly, the actual compression ratio is lowered in the all-premixed fuel gas mode or the partially premixed fuel gas mode and the actual compression ratio is raised in the diffusion fuel gas mode or the diffusion fuel oil mode, so that the operation in the stable premixed fuel gas mode and the operation in the diffusion fuel gas mode or the diffusion fuel oil mode in which the actual compression ratio is raised and a large maximum output is efficiently obtained can be performed.

Further, when the all-premixed fuel gas mode or the partially-premixed fuel gas mode is set, if the actual compression ratio is decreased by changing the closing timing of the exhaust valve 12, the amount of air trapped in the cylinder is decreased, and the maximum output of the internal combustion engine 1 is limited, but in the present embodiment, the amount of pressure increase by the supercharger 16 is increased, and the amount of air trapped in the cylinder is increased, so the maximum output of the internal combustion engine 1 in the all-premixed fuel gas mode or the partially-premixed fuel gas mode can be increased.

[ second embodiment ]

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

The present embodiment differs from the first embodiment only in the configuration of the supercharger 16 that can increase and decrease the supercharging pressure.

As shown in fig. 5, the first supercharger 16C and the second supercharger 16D of the present supercharger 16 are arranged in a side-by-side arrangement. A scavenging connection passage 165a is provided between the compressor 16CC of the first supercharger 16C and the scavenging manifold 20, and an exhaust connection passage 166a is provided between the exhaust turbine 16CT of the first supercharger 16C and the exhaust manifold 14. Further, a scavenging connection passage 165b is provided between the compressor 16DC of the second supercharger 16D and the scavenging manifold 20, and an exhaust connection passage 166b is provided between the exhaust turbine 16DT of the second supercharger 16D and the exhaust manifold 14.

Further, an air cooler 18 is provided in each of the scavenging

connection passages

165a and 165 b.

Opening/closing

valves

167, 168 are inserted into the scavenging connection passage 165b and the exhaust connection passage 166 b.

The first supercharger 16C is always operated, but the second supercharger 16D is operated when the opening and closing

valves

167 and 168 are opened, and is stopped when the opening and closing

valves

167 and 168 are closed.

Since the exhaust pressure is used intensively only by the first supercharger 16C because the exhaust pressure is low at the time of low load of the internal combustion engine 1, and the exhaust pressure is high at the time of high load of the internal combustion engine 1, the exhaust pressure can be used effectively by both the first supercharger 16C and the second supercharger 16D to increase the supercharging amount.

In the present embodiment, when the all-premixed fuel gas mode or the partially-premixed fuel gas mode is set, the first supercharger 16C and the second supercharger 16D are both used to increase the supercharging pressure at the time of high load of the internal combustion engine 1 in the all-premixed fuel gas mode or the partially-premixed fuel gas mode in order to compensate for the reduction in the amount of air trapped in the cylinder. In the diffusion fuel gas mode or the diffusion fuel mode, since the supercharging amount becomes excessive when both the first supercharger 16C and the second supercharger 16D are used, only the first supercharger 16C is used even at the time of high load of the internal combustion engine 1.

Since the control device for a dual-fuel internal combustion engine according to the second embodiment of the present invention and the ship including the control device are configured as described above, as in the first embodiment, when the ship enters the exhaust gas restriction sea area, the entire premixed fuel gas mode or the partially premixed fuel gas mode can be selected, and the ship can be operated in a state where the exhaust gas restriction is released in a state where the NOx emission amount is small, and when the ship leaves the exhaust gas restriction sea area, the diffusion fuel gas mode or the diffusion fuel oil mode can be selected, and the ship can be operated in a state where a large maximum output is efficiently obtained.

Further, since the actual compression ratio is lowered in the all-premixed fuel gas mode or the partially-premixed fuel gas mode and the actual compression ratio is raised in the diffusion fuel gas mode or the diffusion fuel oil mode, as in the first embodiment, both the stable operation in the all-premixed fuel gas mode or the partially-premixed fuel gas mode and the operation in the diffusion fuel gas mode or the diffusion fuel oil mode in which the actual compression ratio is raised and the large maximum output is efficiently obtained can be simultaneously established.

When the all-premixed fuel gas mode or the partially-premixed fuel gas mode is set, the maximum output of the internal combustion engine 1 in the premixed fuel gas mode or the partially-premixed fuel gas mode can be increased by increasing the supercharging amount of the supercharger 16 and increasing the amount of air trapped in the cylinder.

[ others ]

The embodiments of the present invention have been described above, but the present invention can be variously modified in the above embodiments within a range not departing from the gist thereof.

For example, in the case of the all-premixed fuel gas mode or the partial premixed fuel gas mode, as the supercharger 16 capable of increasing the supercharging amount, for example, an electric assist type supercharger can be applied, and the supercharging amount can be increased by using electric assist in the premixed fuel gas mode. Further, a variable displacement supercharger may be applied to increase the displacement and increase the supercharging pressure in the premixed fuel gas mode.

In the above embodiment, the control device 40 determines whether or not the navigation sea area in which the ship is navigating is the exhaust gas restriction sea area, automatically selects the operation mode (combustion mode) of the internal combustion engine 1, but it is also possible to artificially determine whether or not the navigation sea area in which the ship is navigating is the exhaust gas restriction sea area, in the case of the exhaust gas limited sea area, a command for selecting the all-premixed fuel gas mode (all-fuel gas premixed combustion mode) or the partially-premixed fuel gas mode (partial fuel gas premixed combustion mode) is manually issued to an operation mode selection unit (combustion mode selection means) of the control device 40, in the case where the exhaust gas is not limited to the sea area, the operation mode selection unit (combustion mode selection means) of the control device 40 is manually instructed to select the diffusion fuel gas mode or the diffusion fuel mode (fuel gas diffusion combustion mode).

Further, in the above-described embodiment, the present invention exemplifies a dual-fuel internal combustion engine as the internal combustion engine, but the internal combustion engine according to the present invention is not limited to the dual-fuel internal combustion engine, and may be an internal combustion engine (gas engine) that is operated only with fuel gas, as long as it is an internal combustion engine in which at least a fuel gas diffusion combustion method and a fuel gas premix combustion method can be selected during operation, or an internal combustion engine in which at least a fuel gas diffusion combustion method, a fuel gas all-premix combustion method, and a fuel gas partial premix combustion method can be selected during operation.

In addition, in the operation of the internal combustion engine, the amount of change in performance of the internal combustion engine associated with the change in the combustion system can be manipulated in the offset direction based on the control of the actual compression ratio by executing the combustion system selection step of selecting one of the combustion systems including at least the fuel gas diffusion combustion system and the fuel gas premix combustion system or one of the combustion systems including at least the fuel gas diffusion combustion system, the fuel gas all-premix combustion system, and the fuel gas partial premix combustion system, and the compression ratio control step of controlling the actual compression ratio of the internal combustion engine based on the combustion system selected in the combustion system selection step.

Description of the symbols

1 Dual-fuel internal combustion engine (internal combustion engine)

9 cylinder jacket

10 scavenging port

11 Cylinder head

12 exhaust valve

13 piston

14 exhaust manifold

16 pressure booster

30 premix gas valve (first fuel gas injection valve)

32 diffusion gas valve (second fuel gas injection valve)

34 Fuel valve (Fuel injection valve)

40 control device

42 determination unit (determination unit)

44 operation mode selector (combustion mode selector)

46 Fuel injection control part (fuel injection control means)

48 actual compression ratio control section (actual compression ratio control means)

50 boost control part (boost control unit)

Claims

1. A control device for an internal combustion engine, comprising:

a combustion mode selection means capable of selecting at least a fuel gas diffusion combustion mode and a fuel gas premix combustion mode during operation of the internal combustion engine;

a fuel injection control unit that controls fuel injection so that the fuel injection is a fuel injection method corresponding to the combustion method selected by the combustion method selection unit;

actual compression ratio control means for controlling the actual compression ratio so that the actual compression ratio becomes an actual compression ratio corresponding to the combustion method selected by the combustion method selection means;

a determination unit that determines whether or not an exhaust gas restriction state in which the exhaust gas of the internal combustion engine should be restricted,

the combustion mode selection means selects the fuel gas premixed combustion mode when it is determined that the exhaust gas is in the restricted state based on the determination means, selects the fuel gas diffusion combustion mode when it is determined that the exhaust gas is not in the restricted state based on the determination means,

the actual compression ratio control means controls the actual compression ratio to a lower compression ratio than in the case of the fuel gas diffusion combustion method if the fuel gas premixed combustion method is selected, and controls the actual compression ratio to a higher compression ratio than in the case of the fuel gas premixed combustion method if the fuel gas diffusion combustion method is selected.

2. The control apparatus of an internal combustion engine according to claim 1,

the fuel gas premixed combustion method comprises the following steps: a fuel gas premixed combustion system in which only fuel gas is premixed and combusted using fuel gas; and a fuel gas partially premixed combustion system in which a part of the fuel gas is premixed combusted and the remaining fuel gas is diffusion combusted,

the combustion mode selection means is capable of selecting at least the fuel gas diffusion combustion mode, the fuel gas all-premixed combustion mode, and the fuel gas partial-premixed combustion mode during operation of the internal combustion engine, and selects the fuel gas diffusion combustion mode, the fuel gas all-premixed combustion mode, and the fuel gas partial-premixed combustion mode during operation of the internal combustion engine

The actual compression ratio control means controls the actual compression ratio to the low compression ratio if the fuel gas fully premixed combustion mode or the fuel gas partially premixed combustion mode is selected, and controls the actual compression ratio to the high compression ratio if the fuel gas diffusion combustion mode is selected.

3. The control apparatus of an internal combustion engine according to claim 1,

the internal combustion engine is provided with a valve gear capable of changing the closing timing of an exhaust valve,

the actual compression ratio control means controls the actual compression ratio by operating the exhaust valve closing timing, controls the exhaust valve closing timing to a retard angle side at the high compression ratio when controlling the actual compression ratio to the low compression ratio, and controls the exhaust valve closing timing to an advance angle side at the low compression ratio when controlling the actual compression ratio to the high compression ratio.

4. The control device for an internal combustion engine according to any one of claims 1 to 3,

the internal combustion engine is provided with a supercharger capable of increasing and decreasing the supercharging pressure,

and a supercharging control unit that sets the supercharging amount to a normal state when the combustion mode selection unit selects the fuel gas diffusion combustion mode, and sets the supercharging amount to an increased state in which the supercharging amount is increased from the normal state when the combustion mode selection unit selects the fuel gas premix combustion mode, at least in a high-load state in which the load of the internal combustion engine is greater than a fixed load.

5. The control apparatus of an internal combustion engine according to claim 4,

the supercharger is a supercharger capable of switching between two-stage supercharging and single-stage supercharging,

the supercharging control unit sets the supercharger to a single-stage supercharging when the supercharging amount is set to the normal state, and sets the supercharger to a two-stage supercharging when the supercharging amount is set to the increase state.

6. The control apparatus of an internal combustion engine according to claim 4,

when the combustion mode selection means selects the fuel gas diffusion combustion mode, the supercharging control means sets the supercharging amount to an increased state when the load of the internal combustion engine is in a low-load state equal to or less than the predetermined load.

7. The control device for an internal combustion engine according to any one of claims 1 to 3,

the internal combustion engine is a marine internal combustion engine equipped in a ship,

the determination unit determines that the exhaust gas restriction state is present if a navigation sea area in which the ship is navigating is within an exhaust gas restriction sea area, and determines that the exhaust gas restriction state is not present if the navigation sea area is outside the exhaust gas restriction sea area.

8. A ship is characterized in that

A control device for an internal combustion engine according to any one of claims 1 to 7, and the internal combustion engine controlled by the control device.

9. An operation method of an internal combustion engine, comprising:

a determination unit step, a combustion mode selection step, and a compression ratio control step,

in the determination step, it is determined whether or not the exhaust gas restriction state is an exhaust gas restriction state in which the exhaust gas of the internal combustion engine is to be restricted;

a combustion method selection step of selecting one of combustion methods including at least a fuel gas diffusion combustion method and a fuel gas premix combustion method during operation of the internal combustion engine, selecting the fuel gas premix combustion method when it is determined that the internal combustion engine is in the exhaust gas restricted state based on the determination step, and selecting the fuel gas diffusion combustion method when it is determined that the internal combustion engine is not in the exhaust gas restricted state based on the determination step,

in the compression ratio control step, the actual compression ratio of the internal combustion engine is controlled in accordance with the combustion method selected in the combustion method selection step.

10. The method of operating an internal combustion engine according to claim 9,

in the combustion mode selecting step, one combustion mode of the combustion modes including at least the fuel gas diffusion combustion mode, the fuel gas all-premixed combustion mode, and the fuel gas partial-premixed combustion mode is selected during operation of the internal combustion engine.

11. The method of operating an internal combustion engine according to claim 9 or 10,

in the determining step, it is determined that the exhaust gas restricted state is established when a navigation sea area in which the ship is navigating is an exhaust gas restricted sea area, and it is determined that the exhaust gas restricted state is not established when the navigation sea area is outside the exhaust gas restricted sea area.