JP7788926B2 - Marine engines - Google Patents

Description

The present invention relates to a marine engine for use on ships. In particular, it relates to a marine engine that can burn alternative fuels such as ammonia together with conventional fossil fuels.

In recent years, due to the problems of global warming, greenhouse gases such as carbon dioxide (Greenhouse gases)
There is a demand for the realization of zero emissions, which means reducing CO2 emissions to zero. Therefore, alternative fuels such as ammonia, which do not emit greenhouse gases such as carbon dioxide when burned, are attracting attention. However, alternative fuels such as ammonia are harder to burn than fossil fuels, making it difficult to achieve "single-combustion" in which only ammonia is burned.

As a result, so-called "co-firing" marine engines, which burn ammonia and other fuels together with fossil fuels such as diesel fuel, are being considered.

For example, Patent Document 1 below discloses a combustion system in which a fuel injection valve is provided that injects fossil fuel and alternative fuel in layers to mix and burn the fossil fuel and alternative fuel, and the fossil fuel and alternative fuel are injected into the combustion chamber from this fuel injection valve to mix and burn the fossil fuel and alternative fuel.

In the technology of Patent Document 1, for example, when a fossil fuel is used as a pilot fuel for ignition and an alternative fuel is used as the main fuel and injected into the combustion chamber to achieve mixed combustion, increasing the amount of alternative fuel results in unburned residue of the alternative fuel. Therefore, an additional fossil fuel is interposed between the alternative fuels to improve ignition performance, thereby achieving complete mixed combustion.

On the other hand, Patent Document 2 below also proposes sending compressed heated gas to increase the temperature of the combustion chamber in an engine that exclusively burns ammonia, in order to promote the combustion of the ammonia.

Japanese Patent Application Laid-Open No. 2020-180567 Japanese Patent Application Laid-Open No. 2012-202559

Recently, however, the required reduction in greenhouse gas emissions has been increasing, and so even when alternative fuels are mixed, as in Patent Document 1, it is necessary to increase the amount of alternative fuel and increase the proportion of alternative fuel in each fuel injection, the so-called "mixed combustion ratio." However, simply increasing the mixed combustion ratio poses the problem that alternative fuels such as ammonia are difficult to burn, which could result in an increase in unburned residue of alternative fuels such as ammonia, making it impossible to exceed the mixed combustion ratio limit.

As described in Patent Document 2, even in engines that co-combust ammonia and other alternative fuels, it is conceivable to operate the engine with the temperature of the combustion chamber increased to promote the combustion of the ammonia. In this way, by increasing the temperature of the combustion chamber, it is conceivable to reduce the amount of unburned ammonia and other alternative fuels and increase the co-combustion ratio, even in marine engines that co-combust ammonia and other alternative fuels.

However, on ships, engines are not always operated at a constant load, but rather there are situations where they are operated at a low load when the ship is near land, such as when entering or leaving port. In such situations, the combustion of alternative fuels such as ammonia deteriorates, so it may be possible to stop co-firing with alternative fuels and operate the engine solely on fossil fuels such as diesel.

However, if the engine is operated by burning only fossil fuels while the temperature in the combustion chamber is kept high, nitrogen oxides (NOx) will be generated, which will result in a deterioration of exhaust gas performance.

The present invention was made in light of these points, and its purpose is to provide a marine engine that can be used in both high-load and low-load marine navigation situations, and that, when navigating in sea areas at high loads, increases the proportion of alternative fuel such as ammonia, thereby increasing the so-called "mixed-fuel ratio," while, when navigating in sea areas at low loads, suppresses the generation of nitrogen oxides (NOx) and improves exhaust gas performance.

In order to achieve this object, the present invention provides a marine engine that is used in situations where a ship is sailing in an ocean area at high load and situations where the ship is sailing in an ocean area at low load, and is characterized in that when sailing in an ocean area at high load, the engine is operated in a dual-combustion mode in which both alternative fuel and fossil fuel are burned, and a combustion chamber temperature increasing means is activated to increase the combustion chamber temperature, and when sailing in an ocean area at low load, the engine is operated in a normal combustion mode in which fossil fuel is burned, and the combustion chamber temperature increasing means is controlled not to be activated.

Specifically, in a first invention, there is provided a marine engine for use in a situation where a ship is navigating an area of sea at a high load and in a situation where the ship is navigating an area of sea at a low load, the marine engine having a combustion mode selection means which has a dual-combustion mode in which both an alternative fuel and a fossil fuel are injected into the combustion chamber and burned, and a normal combustion mode in which fossil fuel is injected into the combustion chamber and burned, and a combustion chamber temperature increasing means which increases the temperature of the combustion chamber, and in a situation where the ship is navigating an area of sea at a high load, the combustion mode selection means selects the dual-combustion mode and activates the combustion chamber temperature increasing means to control so as to increase the temperature of the combustion chamber, and in a situation where the ship is navigating an area of sea at a low load, the marine engine is characterized by having an engine control means which selects the normal combustion mode with the combustion mode selection means and stops the combustion chamber temperature increasing means to control so as not to increase the temperature of the combustion chamber.

With this configuration, when the ship is sailing in an area of sea at a high load, the combustion mode selection means selects dual-fuel mode and controls the combustion chamber temperature increase means to operate, while when the ship is sailing in an area of sea at a low load, the combustion mode selection means selects normal combustion mode and controls the combustion temperature increase means to stop. In other words, when the engine is operating in dual-fuel mode, the combustion chamber temperature increases, and when the engine is operating in normal combustion mode, the combustion chamber temperature does not increase.

As a result, in dual-fuel combustion mode, the temperature in the combustion chamber rises, so even if a larger amount of alternative fuel is injected, it is possible to prevent unburned alternative fuel, thereby reducing greenhouse gas (especially carbon dioxide) emissions. On the other hand, in normal combustion mode, the temperature in the combustion chamber does not rise, so the generation of nitrogen oxides (NOx) can be reduced.

Here, "fossil fuel" refers to fuels that can be refined from crude oil, such as diesel fuel, distillate oil, and residual oil. On the other hand, "alternative fuel" refers to fuels that can replace natural petroleum, and generally refers to fuels that can replace petroleum, such as ammonia, biofuel, methanol, and ethanol.

"Dual-fuel mode" refers to an engine combustion mode in which fossil fuel and alternative fuel are injected into the combustion chamber and burned together. Note that a single fuel injector may inject both fuels, or multiple fuel injectors may inject the fuels separately.

Furthermore, "normal combustion mode" refers to the engine's combustion mode in which only fossil fuel is injected into the combustion chamber and burned.

In a second aspect of the present invention, the combustion chamber temperature increasing means is a scavenging air temperature increasing means that increases the temperature of the scavenging air introduced into the combustion chamber.

With this configuration, the combustion chamber temperature increasing means is a scavenging air temperature increasing means that increases the temperature of the scavenging air introduced into the combustion chamber, so the temperature of the scavenging air introduced into the combustion chamber is higher than in normal combustion mode.

As a result, the temperature of the introduced scavenging air itself is high, which inevitably increases the temperature in the combustion chamber, making it easier for the alternative fuel to ignite and burn.

This makes it possible to more reliably improve the combustibility of alternative fuels in multi-fuel mode.

In a third aspect of the present invention, the scavenging air temperature increasing means is an air cooler cooling water flow rate limiting mechanism that limits the flow rate of cooling water in the air cooler that cools the scavenging air.

With this configuration, the scavenging air temperature increasing means is an air cooler cooling water flow restriction mechanism that restricts the flow rate of the cooling water in the air cooler that cools the scavenging air, so the cooling performance of the air cooler can be reduced and the temperature of the scavenging air introduced into the combustion chamber can be increased.

Therefore, by simply restricting the flow rate of the cooling water in the air cooler (structure), it is possible to increase the temperature of the scavenging air and therefore the temperature in the combustion chamber.

This allows for the construction of a scavenging air temperature increasing means using a simple method (structure), and also increases the proportion of alternative fuels used in mixed combustion.

In a fourth aspect of the present invention, the scavenging air temperature increasing means is an air cooler coolant temperature increasing mechanism that increases the temperature of the coolant in the air cooler that cools the scavenging air.

With this configuration, the scavenging air temperature increasing means is an air cooler coolant temperature increasing mechanism that increases the temperature of the coolant in the air cooler that cools the scavenging air, so the cooling performance of the air cooler can be reduced and the temperature of the scavenging air can be increased without changing the flow rate of the coolant flowing through the air cooler.

This allows the temperature of the scavenging air to be increased and the temperature of the combustion chamber to be raised without reducing the flow rate of cooling water flowing through the air cooler.

This allows the flow rate of cooling water in the air cooler to be kept constant at all times, reducing the risk of air cooler failure. It also allows for a higher ratio of alternative fuels in mixed combustion.

In a fifth aspect of the present invention, the combustion chamber temperature increasing means is an engine cylinder coolant flow rate limiting mechanism that limits the flow rate of coolant that cools the engine cylinder.

With this configuration, the combustion chamber temperature increasing means is an engine cylinder coolant flow rate limiting mechanism that limits the flow rate of the coolant that cools the engine cylinder. Therefore, the flow rate of the coolant that cools the engine cylinder is limited, causing the temperature of the engine cylinder to rise, which in turn increases the temperature of the combustion chamber provided in that engine cylinder.

This means that the temperature in the combustion chamber can be increased by the simple method (structure) of restricting the flow rate of the cooling water that cools the engine cylinder.

Therefore, by using the simple method (structure) of restricting the flow rate of cooling water in the engine cylinder, it is possible to create a means of increasing the combustion temperature and also increase the proportion of alternative fuels that can be mixed and burned.

In a sixth aspect of the present invention, the combustion chamber temperature increasing means is an exhaust valve advance mechanism that advances the closing timing of the exhaust valve.

With this configuration, the combustion chamber temperature increasing means is an exhaust valve advance mechanism that advances the closing timing of the exhaust valve, thereby accelerating the closing timing of the exhaust valve. This lengthens the period during which the air is compressed by the piston. In this way, the longer the compression period, the higher the temperature of the air, and as a result, the higher the temperature of the combustion chamber.

For this reason, by advancing the exhaust valve closing timing (structure), the period during which the air is compressed can be extended, thereby increasing the temperature in the combustion chamber.

This allows for the creation of a combustion chamber temperature raising means without affecting the engine's cooling system. It also allows for a higher mixed-fuel ratio, which is the proportion of alternative fuels used.

In the seventh invention, the combustion chamber temperature increasing means is a hot bulb communication mechanism that connects the combustion chamber to a hot bulb chamber in which a hot bulb, which serves as a heat source, is placed.

With this configuration, the combustion chamber temperature increasing means is a bulb connection mechanism that connects the combustion chamber to the bulb chamber in which the bulb, which serves as a heat source, is placed. When the bulb connection mechanism is activated, the air in the combustion chamber is heated by the bulb, which serves as a heat source.

This ensures that the temperature in the combustion chamber increases, allowing for a higher proportion of alternative fuels to be mixed.

This ensures that the combustion chamber temperature can be increased, increasing the mixed combustion rate, which is the proportion of alternative fuels.

As explained above, according to the present invention, in dual-fuel combustion mode, the temperature in the combustion chamber rises, so even if a larger amount of alternative fuel is injected, unburned alternative fuel is prevented, and greenhouse gas (particularly carbon dioxide) emissions can be reduced. On the other hand, in normal combustion mode, the temperature in the combustion chamber does not rise, so the generation of nitrogen oxides (NOx) can be reduced.

Therefore, a marine engine that is used in both high-load and low-load sea navigation can increase the ratio of alternative fuels such as ammonia during high-load sea navigation, thereby increasing the so-called "mixed-fuel ratio," while suppressing the generation of nitrogen oxides (NOx) and improving exhaust gas performance during low-load sea navigation.

1 is a schematic diagram illustrating a configuration of a marine engine according to a first embodiment of the present invention. FIG. 1 is a system schematic diagram showing a system configuration of a fuel injection device according to a first embodiment. FIG. 2 is a detailed longitudinal sectional view showing a combustion chamber of a marine engine. 1 is a schematic diagram of an intake and exhaust system and a cooling system of a marine engine according to a first embodiment. 4 is a main control flowchart according to the first embodiment. 4 is a sub-control flowchart according to the first embodiment. FIG. 10 is a schematic diagram of an intake and exhaust system and a cooling system of a marine engine according to a second embodiment. 10 is a sub-control flowchart according to a second embodiment. FIG. 10 is a schematic diagram of an intake and exhaust system and a cooling system of a marine engine according to a third embodiment. 10 is a sub-control flowchart according to a third embodiment. FIG. 10 is a schematic diagram of an intake and exhaust system and a cooling system of a marine engine according to a fourth embodiment. 10 is a sub-control flowchart according to a fourth embodiment. FIG. 10 is a schematic diagram illustrating the configuration of a marine engine according to a fifth embodiment. FIG. 10 is a system schematic diagram showing an exhaust valve device according to a fifth embodiment. 10 is a control flowchart of an exhaust valve device according to a fifth embodiment. 10 is a sub-control flowchart according to a fifth embodiment. FIG. 10 is a schematic diagram illustrating the configuration of a marine engine according to a sixth embodiment. 13 is a sub-control flowchart according to a sixth embodiment.

Embodiments of the present invention are described in detail below with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

(Embodiment 1)
Fig. 1 is a schematic diagram showing the configuration of a marine engine for a ship, Fig. 2 is a system schematic diagram showing the system configuration of a fuel injection device, Fig. 3 is a detailed longitudinal cross-sectional view showing the combustion chamber of the marine engine, and Fig. 4 is a schematic diagram of the intake and exhaust system and cooling system of the marine engine. Using these figures, we will first provide an overview of the marine engine 1. Hereinafter, the marine engine 1 for a ship will be simply referred to as "engine 1."

Engine 1 is an in-line multi-cylinder marine engine equipped with multiple cylinders 10. For convenience, only one cylinder will be shown in the present embodiment. Engine 1 is configured as a two-stroke, one-cycle engine that employs a uniflow scavenging system, and is installed on large ships such as tankers, container ships, and car carriers.

Engine 1 installed on a vessel is used as the main engine for propelling the vessel. That is, the output shaft of engine 1 is connected to the vessel's propeller (not shown) via a propeller shaft (not shown). When engine 1 is operated, its output is transmitted to the propeller, propelling the vessel.

In particular, the engine 1 according to this embodiment is configured as a so-called crosshead type internal combustion engine in order to achieve a long stroke. That is, in this engine 1, a piston rod 22 that supports the piston 21 from below and a connecting rod 24 that is connected to the crankshaft 23 are connected by a crosshead 25.

The engine 1 also includes a base plate 11 located below, a frame 12 mounted on the base plate 11, and a cylinder jacket 13 mounted on the frame 12. The base plate 11, frame 12, and cylinder jacket 13 are fastened together by a plurality of tie bolts B extending in the vertical direction and nuts. The engine 1 also includes a cylinder 10 mounted within the cylinder jacket 13, a piston 21 mounted within the cylinder 10, and an output shaft (e.g., crankshaft 23) that rotates in conjunction with the reciprocating motion of the piston 21.

The base plate 11 constitutes the so-called crankcase of the engine 1 and houses the crankshaft 23 and a bearing 26 that rotatably supports the crankshaft 23. The lower end of a connecting rod 24 is connected to the crankshaft 23 via a crank 27.

The frame 12 houses a pair of guide plates 28, 28, a connecting rod 24, and a crosshead 25. The pair of guide plates 28, 28 are made of a pair of plate-shaped members arranged along the piston axial direction and are spaced apart in the width direction of the engine 1 (left-right direction on the paper in Figure 1). The connecting rod 24 is positioned between the pair of guide plates 28, 28, with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via the crosshead 25.

Specifically, the crosshead 25 is disposed between a pair of guide plates 28, 28, and slides up and down along each of the guide plates 28, 28. That is, the pair of guide plates 28, 28 are configured to guide the sliding of the crosshead 25. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The crosshead pin 29 is connected to the piston rod 22 so that they can move up and down together, and is connected to the connecting rod 24 so that the connecting rod 24 can rotate around the upper end of the connecting rod 24 as a fulcrum.

The cylinder jacket 13 has a cylinder liner 14 positioned inside it as an inner cylinder. The aforementioned piston 21 is positioned inside the cylinder liner 14. This piston 21 reciprocates up and down along the inner wall of the cylinder liner 14. A cylinder cover 15 is fixed to the top of the cylinder liner 14. The cylinder cover 15, together with the cylinder liner 14, constitutes the cylinder 10.

The cylinder cover 15 is also provided with an exhaust valve 18 that is operated by an exhaust valve device (not shown in Figure 1). The exhaust valve 18, together with the cylinder 10, which is made up of the cylinder liner 14 and cylinder cover 15, and the top surface of the piston 21, defines the combustion chamber 17. The exhaust valve 18 opens and closes the connection between the combustion chamber 17 and an exhaust pipe 19. The exhaust pipe 19 has an exhaust port (not shown) that leads to the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

The cylinder cover 15 also defines the ceiling surface of the combustion chamber 17. A fuel injection valve 30 is provided on this ceiling surface.

As shown in Figure 3, this fuel injection valve 30 is positioned so as to face the interior of the combustion chamber 17, and has an injection port 31 that injects fossil fuel and alternative fuel, or fossil fuel only. For convenience, Figure 3 shows one fuel injection valve 30, but in this embodiment, three fuel injection valves 30 are provided for each cylinder.

Specifically, the fuel injection valve 30 is arranged with its injection port 31 facing inside the combustion chamber 17, and is configured to inject fuel in layers with the fossil fuel and alternative fuel arranged alternately.

Here, the alternative fuel functions as the main fuel that generates power for engine 1, and the fossil fuel functions as the pilot fuel for igniting the main fuel. In this embodiment, diesel fuel is used as the fossil fuel, and ammonia is used as the alternative fuel. Therefore, the alternative fuel in this embodiment has a higher ignition temperature, at which compression ignition occurs, than fossil fuel.

Although not specifically shown, this fuel injection valve 30 may also inject fuel using only fossil fuel, without using alternative fuel. In this case, as is well known, the fossil fuel is injected into the combustion chamber in a single layer.

The fuel injection device 100 that supplies fuel to this fuel injection valve 30 will be described later using Figure 2.

In this way, the fuel injection valve 30 injects the fossil fuel and alternative fuel into the combustion chamber 17, causing both to combust within the combustion chamber 17. This combustion of the fossil fuel and alternative fuel within the combustion chamber 17 is called "mixed combustion." Details of "mixed combustion" will be provided later.

This combustion causes the piston 21 shown in Figure 1 to reciprocate up and down. At this time, when the exhaust valve 18 operates and the combustion chamber 17 opens, exhaust gases generated by the combustion are pushed out into the exhaust pipe 19, and scavenging air is introduced into the combustion chamber 17 from a scavenging port (not shown) located below.

When the piston 21 reciprocates due to this combustion, the piston rod 22 reciprocates up and down along with the piston 21. This causes the crosshead 25 connected to the piston rod 22 to reciprocate up and down. This crosshead 25 allows the connecting rod 24 to rotate, causing the connecting rod 24 to rotate around the connection point with the crosshead 25 as a fulcrum. The crank 27 connected to the lower end of the connecting rod 24 then performs a crank motion, and the crankshaft 23 rotates in response to this crank motion. In this way, the crankshaft 23 converts the reciprocating motion of the piston 21 into rotational motion, and rotates the ship's propeller together with the propeller shaft. This propels the ship.

Next, using Figure 2, we will explain the fuel injection device 100 that supplies fuel to the fuel injection valve 30.

This fuel injection device 100 includes a fuel pump 41 that pumps fossil fuel to the fuel injection valve 30, and an injection pump 51 that injects alternative fuel into the path through which the fossil fuel is pumped.

The fuel pump 41 and injection pump 51 are located near the cylinder 10 as shown in Figure 1, and are connected to the fuel injection valve 30 via the first internal passage 32, fuel injection pipe 42, second internal passage 33, injection pipe 52, etc., respectively.

Of these, the fuel pump 41 is connected to the fuel injection valve 30 via a fossil fuel path L that runs from the fuel pump 41 to the injection nozzle 31, and pumps fossil fuel toward the fuel injection valve 30. This fossil fuel path L consists of a first internal path 32 and a fuel injection pipe 42 (including the branch pipe 42a, etc., described below), and is configured as a path connecting the fuel pump 41 and the injection nozzle 31.

The injection pump 51 is also connected to the fossil fuel path L via the second internal path 33 and the injection pipe 52, and injects alternative fuel into this fossil fuel path L.

This configuration allows the fuel injection valve 30 to inject the fossil fuel pumped by the fuel pump 41 and the alternative fuel injected by the injection pump 51 into the combustion chamber 17 in a stratified manner.

As mentioned above, the engine of this embodiment is provided with three fuel injection valves 30... for each cylinder. Therefore, in order to supply fossil fuel and alternative fuel to each fuel injection valve 30..., the fuel injection pipe 42 and the injection pipe 52 are branched into three branch pipes (42a, 42b, 42c, 52a, 52b, 52c) via branch sections 43, 53, respectively.

The fuel pump 41, which pumps fossil fuel into the fuel injection pipe 42 and the injection pump 51, which injects alternative fuel into the injection pipe 52, are controlled by the control unit 92. Specifically, the control signal sent from the control unit 92 controls the fuel control valve 45 and the injection control valve 55, thereby controlling the operation of the fuel pump 41 and the injection pump 51.

This control unit 92 is connected to a detection unit 91 that detects various signals such as the engine crank angle, and is configured to control the operation of the fuel pump 41 and injection pump 51 based on the various signals detected by this detection unit 91. Note that dashed lines in Figure 2 indicate electrical connections.

The fuel pump 41 is connected to a fuel tank (not shown) that stores fossil fuel via piping or the like (not shown), and is configured to receive fossil fuel from this fuel tank.

Meanwhile, an alternative fuel supply pump 71 that supplies alternative fuel is connected to the injection pump 51 via a supply pipe 72, allowing the alternative fuel to be supplied. This alternative fuel supply pump 71 is also connected via piping or the like (not shown) to an alternative fuel tank (not shown) in which alternative fuel is stored, and is configured to receive alternative fuel from this alternative fuel tank.

In addition, a pressure accumulator 81 is connected to the fuel pump 41 and the injection pump 51. This pressure accumulator 81 accumulates pressure in the hydraulic oil that operates the fuel pump 41 and the injection pump 51. The pressure accumulator 81 is connected to a high-pressure pump 82, and is configured to store and accumulate pressure in the hydraulic oil pumped from the high-pressure pump 82.

In addition, check valves 73, 54, and 34 are provided at each location in the alternative fuel path (supply pipe 72, injection pipe 52, and second internal path 33) through which the alternative fuel is injected to prevent backflow of the alternative fuel.

With the fuel injection device 100 configured in this manner, in the engine 1 of this embodiment, as described below, when the ship is sailing in sea areas under high load, the control unit 92 operates in a so-called "mixed combustion mode" in which both fossil fuel and alternative fuel are injected into the combustion chamber 17 from the fuel injection valves 30, resulting in mixed combustion within the combustion chamber 17.

On the other hand, when the ship is sailing in the sea area at low load, the control unit 92 stops the operation of the alternative fuel injection pump 51, and the fuel injection valves 30... operate in so-called "normal combustion mode," in which only fossil fuel is injected into the combustion chamber 17, and normal combustion occurs within the combustion chamber 17.

Next, the intake and exhaust systems and cooling systems of the engine 1 of this embodiment will be explained using Figure 4.

The intake and exhaust system AL of the engine 1 is composed of a turbocharger 101 that takes in outside air from the upstream side and compresses the air, an air cooler 102 that cools the compressed air, a drain separator 103 that removes condensed water from the cooled air, a scavenging chamber 104 that stores compressed air before scavenging (introducing) it into the combustion chamber 17, the combustion chamber 17 provided in the cylinder jacket 13, an exhaust pipe 105 that directs exhaust gases discharged from the combustion chamber 17 downstream, and an exhaust path 106 that guides the exhaust gases directed to the exhaust pipe 105 back to the turbocharger 101.

By configuring the intake and exhaust system AL of the engine 1 in this way, fresh outside air is first compressed in the turbocharger 101, increasing the air density before being sent to the engine 1. However, as the temperature of the air rises when it is compressed, this compressed air is cooled in the air cooler 102. However, as cooling the compressed air generates condensed water (drain), this condensed water is removed by a drain separator 103 installed downstream. The compressed air from which the condensed water has been removed is stored in the scavenging chamber 104, and this compressed air scavenges from the scavenging chamber 104 into the combustion chamber 17 of the cylinder jacket 13.

After the fuel is burned in the combustion chamber 17 using the compressed air, the exhaust gas is scavenged with compressed air from the next cycle and collected in the exhaust pipe 105. The collected exhaust gas is guided to the turbocharger 101 via the exhaust path 106, activates the turbocharger 101, and is then discharged to the outside.

Engine 1's cooling system consists of two systems: a high-temperature cooling system HCL and a low-temperature cooling system LCL.

The high-temperature cooling system HCL is a system that cools the cylinder jacket 13 of the engine 1. The high-temperature cooling system HCL is equipped with a seawater heat exchanger 107 that uses seawater to cool the fresh water cooling water, and a pump device 108 that circulates the fresh water cooling water through the high-temperature cooling system HCL. The high-temperature cooling system HCL is also equipped with a bypass path 109 that does not pass through the seawater heat exchanger 107.

In this high-temperature cooling system HCL, fresh water, which serves as cooling water flowing through the high-temperature cooling system HCL, is cooled in a seawater heat exchanger 107, and the cooled fresh water is sent into the cylinder jacket 13 of the engine 1 using a pump device 108. As the fresh water sent into the cylinder jacket 13 flows within the cylinder jacket 13, it removes heat held by the cylinder jacket 13 and cools it.

On the other hand, the low-temperature cooling system LCL is a system that cools the air cooler 102 that cools the engine intake air (compressed air), and is equipped with a seawater heat exchanger 110 on the path of the low-temperature cooling system LCL that uses seawater to cool the fresh water or seawater cooling water, and a pump device 101 that circulates the fresh water or seawater cooling water through the path of the low-temperature cooling system LCL.

The low-temperature cooling system LCL also has a bypass path 112 that bypasses the air cooler 102. A bypass valve 113 and a restriction valve 114 are provided midway along this bypass path 112 and near the inlet of the air cooler 102, respectively. The bypass valve 113 and restriction valve 114 are configured to be switched on and off in response to signals from the control unit 92.

In this low-temperature cooling system LCL, fresh water or seawater, which serves as cooling water flowing through this path, is sent to a seawater heat exchanger 110 using a pump device 111, where the fresh water or seawater is cooled, and the cooled fresh water or seawater is sent to an air cooler 102. The fresh water or seawater sent to the air cooler 102 cools the compressed air, the temperature of which has risen.

In addition, this low-temperature cooling system LCL is configured to change the cooling performance of the air cooler 102 by controlling the bypass valve 113 and the restriction valve 114 to change the flow path of the fresh water or seawater cooling water. In other words, by opening the bypass valve 113 and closing the restriction valve 114, the fresh water or seawater cooling water flows into the bypass path 112 and does not flow into the air cooler 102, thereby reducing the cooling performance of the air cooler 102 and preventing the compressed air passing through the air cooler 102 from being cooled.

In this way, in this embodiment, the cooling performance of the air cooler 102 is changed and the temperature of the compressed air is altered by controlling the bypass valve 113 and the restriction valve 114. Note that the bypass valve 113 and the restriction valve 114 may be controlled to partially open or partially close them, allowing for fine adjustment of the amount of cooling water flowing into the air cooler 102.

The control unit 92 shown in Figure 4 is configured to send control signals to the fuel pump 41 that pumps fossil fuel to each fuel injection valve 30, and to the injection pump 51 that pumps alternative fuel.

This embodiment, configured as described above, is controlled in accordance with the main control flowchart shown in Figure 5 and the sub-control flowchart shown in Figure 6.

First, as shown in Figure 5, in S1, the control unit 92 of this engine 1 reads from the detection unit 91 various information (various signals) necessary for engine control, such as the current location of the vessel from GPS signals, the vessel's operating status, and even pilot operation information.

Next, in S2, information such as the ship's current location is used to determine whether the ship is currently in an area where it will be operating under high load. Specifically, if the area is not close to land, such as when entering or leaving a port, it is determined whether the ship will be operating under high load.

If S2 determines that the area is one where high loads will be applied, it will move to S3; if S2 determines that the area is not one where high loads will be applied, it will move to S5.

If it is determined that the waters where the ship is currently located are waters where high loads are likely to occur, then in S3, the engine 1 is operated in mixed combustion mode. That is, both fossil fuel and alternative fuel are injected from the fuel injection valve 30 into the combustion chamber 17, and the fossil fuel and alternative fuel are mixed and burned in the combustion chamber 17. Specifically, the fuel pump 41 and injection pump 51 are operated, and the fossil fuel and alternative fuel are injected in layers from the fuel injection valve 30 into the combustion chamber 17, and the fossil fuel and alternative fuel are mixed and burned in the combustion chamber 17.

Then, the process proceeds to S4, where the combustion chamber temperature increasing means is activated. The control flow for the operation of this combustion chamber temperature increasing means will be explained later in Figure 6(a).

Then, it transitions to return to prepare for the next control cycle.

On the other hand, if the current location of the ship is not in an area where high-load navigation is possible, the engine 1 is operated in normal combustion mode in S5. That is, only fossil fuel is injected from the fuel injection valve 30 into the combustion chamber 17, and only fossil fuel is burned in the combustion chamber 17. Specifically, only the fuel pump 41 is operated, and only fossil fuel is injected in a single layer from the fuel injection valve 30 into the combustion chamber 17, and only fossil fuel is burned in the combustion chamber 17.

Then, the process proceeds to S6, where the combustion chamber temperature increasing means is stopped. The control flow for stopping the combustion chamber temperature increasing means will also be explained later in Figure 6(b).

Finally, it transitions to return to prepare for the next control cycle.

In this embodiment, in S2, it is determined whether the ship is currently operating in an area where it is operating under high load, based on information such as the ship's current location. However, if the pilot operates the engine in a way that puts it under high load, it may be determined that the ship is operating under high load based on that operation information, and the process may proceed to S3.

Next, the activation and deactivation of the combustion chamber temperature increasing means will be explained using the sub-control flow in Figure 6. Note that, hereafter, this will be referred to as the "combustion chamber temperature increasing means (1)" to refer to the combustion chamber temperature increasing means of embodiment 1.

As shown in Figure 6(a), the combustion chamber temperature increasing means (1) operates by opening the bypass valve 113 of the bypass path 112 of the air cooler 102 in S11. Then, in S12, the restriction valve 114, which restricts the amount of cooling water in the air cooler 102, is closed. In other words, the bypass valve 113 and restriction valve 114 are controlled to prevent fresh water or seawater from flowing into the bypass path 112 and into the air cooler 102.

Note that since both the bypass valve 113 and the restriction valve 114 are mechanisms that can restrict the flow rate of the air cooler 102, the control flow may be configured using only either S11 or S12.

On the other hand, as shown in Figure 6(b), to stop the combustion chamber temperature increasing means (1), in S13, the bypass valve 113 of the bypass path 112 of the air cooler 102 is closed. Then, in S14, the restriction valve 114 that restricts the amount of cooling water in the air cooler 102 is opened. In other words, the bypass valve 113 and restriction valve 114 are controlled so that fresh water or seawater cooling water does not flow into the bypass path 112, but fresh water or seawater cooling water flows into the air cooler 102.

In this way, by controlling the bypass valve 113 and the restriction valve 114, the compressed air scavenged into the combustion chamber 17 of engine 1 is supplied to the combustion chamber 17 at a high temperature when the engine is operating in dual-fuel mode in high-load navigation areas, resulting in an increase in the temperature of the combustion chamber 17.

However, when engine 1 is operated in normal combustion mode in general waters that are not subject to high-load navigation, the compressed air is cooled and supplied to combustion chamber 17, so the temperature of combustion chamber 17 does not rise.

In this way, by controlling the bypass valve 113 and the restriction valve 114 to function as a combustion chamber temperature increasing means (1), the temperature of the combustion chamber 17 increases when the engine 1 is operated in dual combustion mode in sea areas where the ship is sailing under high load, whereas the temperature of the combustion chamber 17 does not increase when the engine 1 is operated in normal combustion mode in general sea areas.

In this way, by changing the temperature of the combustion chamber 17, when the engine 1 is operated in the dual-fuel mode, the combustion chamber temperature increases, making the alternative fuel easier to ignite and burn, thereby reducing the risk of unburned fuel remaining and enabling the ratio of the alternative fuel to be increased, thereby increasing the so-called dual-fuel ratio.

On the other hand, when engine 1 is operated in normal combustion mode, the combustion chamber temperature does not rise, so when fossil fuel is burned, the combustion temperature does not rise and nitrogen oxides (NOx) and other substances are not generated, thereby improving exhaust gas performance.

In this way, in this embodiment, by changing the temperature of the combustion chamber 17 when the engine 1 is operated in dual-fuel mode and normal combustion mode, engine performance can be improved in each combustion mode.

As described above, in this embodiment, the engine 1 is for a ship capable of operating in both high-load and low-load sea areas. It has a dual-fuel mode in which both alternative fuel and fossil fuel are injected into the combustion chamber 17 and burned, and a normal combustion mode in which only fossil fuel is injected into the combustion chamber 17 and burned. It also has a combustion chamber temperature increasing means (1) that increases the temperature of the combustion chamber 17. When the ship is operating in high-load sea areas, the dual-fuel mode is selected and the combustion chamber temperature increasing means (1) is activated to increase the temperature of the combustion chamber 17. When the ship is operating in low-load sea areas, the engine 1 selects the normal combustion mode and stops the combustion chamber temperature increasing means (1) to prevent the temperature of the combustion chamber 17 from increasing.

The combustion chamber temperature increasing means (1) in embodiment 1 increases the temperature of the scavenging air introduced into the combustion chamber 17, and specifically includes a bypass valve 113 and a restriction valve 114 provided in the low-temperature cooling system LCL. By controlling the bypass valve 113 and the restriction valve 114 as described above, the flow path of the cooling water in the air cooler 102 is switched to the bypass path 112, the cooling performance of the air cooler 102 decreases, the temperature of the compressed air increases, and the temperature of the combustion chamber 17 increases.

As a result, when the ship is sailing in sea areas under high load, the engine 1 is operated in dual-fuel mode and the combustion chamber temperature increasing means (1) is activated and controlled to increase the temperature of the combustion chamber 17, so that when the engine 1 is operated in dual-fuel mode, the temperature of the combustion chamber 17 increases.

This reduces the risk of unburned alternative fuel remaining when burning in dual-fuel mode, and as a result, the proportion of alternative fuel, or the so-called dual-fuel ratio, can be increased. In other words, by increasing the temperature of the combustion chamber 17, the alternative fuel becomes easier to ignite and burn, allowing for an increased dual-fuel ratio.

On the other hand, when the ship is sailing in the sea area at low load, the engine 1 is operated in normal combustion mode, and the combustion chamber temperature increasing means (1) is not activated and is controlled so as not to increase the temperature of the combustion chamber 17. Therefore, when the engine is operated in normal combustion mode, the temperature of the combustion chamber 17 does not increase.

This reduces the generation of NOx that can occur when burning in normal combustion mode, improving exhaust gas performance.

Therefore, the marine engine 1 is used in situations where the vessel is sailing in sea areas at high load and situations where the vessel is sailing in sea areas at low load. When the vessel is sailing in sea areas at high load, the ratio of alternative fuel such as ammonia is increased, thereby increasing the so-called "mixed combustion ratio," while when the vessel is sailing in sea areas at low load, the generation of nitrogen oxides (NOx) is suppressed, improving exhaust gas performance.

In addition, in this embodiment, the bypass valve 113 and restriction valve 114 provided in the low-temperature cooling system are configured to switch the flow path of the cooling water in the air cooler 102, thereby increasing the temperature of the scavenging air introduced into the combustion chamber 17.

This increases the temperature of the scavenging air introduced into the combustion chamber 17 compared to normal combustion mode.

As a result, the temperature of the introduced scavenging air itself is high, which inevitably increases the temperature of the combustion chamber 17, making it easier for the alternative fuel to ignite and burn.

This ensures improved combustibility during mixed combustion.

In addition, in this embodiment, the restriction valve 114 and bypass valve 113 configure the combustion chamber temperature increasing means (1) by restricting the flow rate of the cooling water in the air cooler 102, which cools the scavenging air.

This allows the temperature of the scavenging air to be increased and the temperature of the combustion chamber 17 to be increased by the simple method (structure) of restricting the flow rate of the cooling water in the air cooler 102.

Therefore, the scavenging air temperature increasing means (1) can be constructed using a simple method (structure), which results in an increase in the temperature of the combustion chamber 17 and an increase in the mixed combustion ratio of alternative fuels.

In this embodiment, the restriction valve 114 and bypass valve 113 are controlled only by opening and closing, but they may also be controlled, for example, by partially opening and partially closing, to slightly throttle the flow of cooling water through the air cooler 102. Furthermore, the restriction valve 114 and bypass valve 113 may also be configured to function as a single two-way valve.

(Embodiment 2)
Next, a second embodiment will be described. The second embodiment will be described using a schematic diagram of an intake/exhaust system and a cooling system of a marine engine in Figure 7 and a sub-control flowchart in Figure 8. Since the other components are the same as those in the first embodiment, the same reference numerals will be used and the description will be omitted.

In this second embodiment, the temperature of the combustion chamber 17 is changed by changing the cooling performance of the air cooler 102, without switching the flow path of the cooling water in the air cooler 102 as in the first embodiment.

Specifically, as shown in Figure 7, a cooling valve 201 is provided at the seawater inlet of the seawater heat exchanger 110 provided in the low-temperature cooling system LCL, and the cooling performance of the air cooler 102 is changed by controlling the opening and closing of this cooling valve 201 using the control unit 92.

Control in this embodiment is performed according to the sub-control flowchart in Figure 8. That is, when the combustion chamber temperature increasing means is activated, corresponding to S4 in the main control flowchart in Figure 5, the control flow for operating the combustion chamber temperature increasing means (2) in Figure 8(a) is performed, and when the combustion chamber temperature increasing means is stopped, corresponding to S6 in the main control flowchart in Figure 5, the control flow for stopping the combustion chamber temperature increasing means (2) in Figure 8(b) is performed. Note that "combustion chamber temperature increasing means (2)" is also referred to as the combustion chamber temperature increasing means of embodiment 2.

When the combustion chamber temperature increasing means (2) is operating, the cooling valve 201 of the seawater heat exchanger 110 is closed in S21. On the other hand, when the combustion chamber temperature increasing means (2) is stopped, the cooling valve 201 of the seawater heat exchanger 110 is opened in S22.

In this way, by controlling the cooling valve 201, first, when the cooling valve 201 is closed, the cooling performance of the seawater heat exchanger 110 decreases and the cooling water flowing through the low-temperature cooling system LCL cannot be cooled. As a result, the temperature of the cooling water flowing through the air cooler 102 increases, the cooling performance of the air cooler 102 decreases, and the temperature of the air scavenged into the combustion chamber 17 increases. As a result, the temperature of the combustion chamber 17 increases.

On the other hand, when the cooling valve 201 is opened, the cooling performance of the seawater heat exchanger 110 improves, the cooling water flowing through the low-temperature cooling system LCL is cooled, and the temperature of the cooling water flowing through the air cooler 102 decreases. This improves the cooling performance of the air cooler 102, lowering the temperature of the air scavenged into the combustion chamber 17. As a result, the temperature of the combustion chamber 17 decreases.

In this way, the temperature of the combustion chamber 17 can be changed by controlling the opening and closing of the cooling valve 201.

As described above, in this embodiment, the combustion chamber temperature increasing means (2) increases the temperature of the scavenging air, and specifically, is a cooling valve 201 that can adjust the temperature of the cooling water in the air cooler 102 that cools the scavenging air.

This allows the cooling performance of the air cooler 102 to be reduced and the temperature of the scavenging air to be increased without changing the flow rate of the cooling water flowing through the air cooler 102.

This allows the temperature of the scavenging air to be increased without reducing the flow rate of the cooling water flowing through the air cooler 102, thereby increasing the temperature of the combustion chamber 17.

As a result, the flow rate of the cooling water in the air cooler 102 can be kept constant at all times, reducing the risk of failure of the air cooler 102. Furthermore, by increasing the temperature of the combustion chamber 17, the proportion of alternative fuels used in mixed combustion can be increased.

In this embodiment, only the control of opening or closing the cooling valve 201 has been described, but it is also possible to open it partially, slightly reducing the amount of seawater, and maintain the cooling performance of the seawater heat exchanger 110.

(Embodiment 3)
Next, a third embodiment will be described. The third embodiment will be described using a schematic diagram of an intake/exhaust system and a cooling system of a marine engine in Fig. 9 and a sub-control flowchart in Fig. 10. The third embodiment is similar to the second embodiment, and other configurations are similar to the first embodiment, so the same reference numerals will be used and the description will be omitted.

In this third embodiment, the temperature of the combustion chamber 17 is changed by making improvements to the high-temperature cooling system HCL.

Specifically, as shown in Figure 9, a cylinder cooling water channel valve 301 is provided in the path of the high-temperature cooling system HCL, and the temperature of the combustion chamber 17 is changed by controlling the opening and closing of this channel valve 301 using the control unit 92.

The control of this embodiment is performed according to the sub-control flowchart of Figure 10. That is, the operation of the combustion chamber temperature increasing means corresponding to S4 in the main control flowchart of Figure 5 is performed according to the control flow for the operation of the combustion chamber temperature increasing means (3) in Figure 10(a), and the stop of the combustion chamber temperature increasing means corresponding to S6 in the main control flowchart of Figure 5 is performed according to the control flow for the stop of the combustion chamber temperature increasing means (3) in Figure 10(b). Note that the "combustion chamber temperature increasing means (3)" is also referred to as the combustion chamber temperature increasing means of the third embodiment.

When the combustion chamber temperature increasing means (3) is operating, the cylinder cooling water channel valve 301 is closed in S31. On the other hand, when the combustion chamber temperature increasing means (3) is stopped, the cylinder cooling water channel valve 301 is opened in S32.

In this way, by controlling the cylinder cooling water channel valve 301, first, when the water channel valve 301 is closed, cooling water does not flow into the engine cylinder 13, so the engine cylinder 13 is heated, and the combustion chamber 17 provided in the engine cylinder 13 itself is also heated. As a result, the temperature of the combustion chamber 17 increases.

On the other hand, when the water passage valve 301 is opened, cooling water flows into the engine cylinder 13, cooling the engine cylinder 13 and also cooling the combustion chamber 17 of the engine cylinder 13. As a result, the temperature of the combustion chamber 17 decreases.

In this way, by controlling the opening and closing of the water channel valve 301, the temperature of the combustion chamber 17 can be changed in this embodiment as well.

As described above, in this embodiment, the combustion chamber temperature increasing means (3) increases the temperature of the combustion chamber 17 itself, and specifically, is a water channel valve 301 that limits the flow rate of the cooling water that cools the engine cylinder 13.

This reduces the flow rate of the cooling water that cools the engine cylinder 13, causing the temperature of the engine cylinder 13 to rise, which in turn increases the temperature of the combustion chamber 17 located within the engine cylinder 13.

This allows the temperature in the combustion chamber 17 to be increased, increasing the proportion of alternative fuels in the mixed combustion.

Therefore, by simply limiting the flow rate of cooling water to the engine cylinder 13, it is possible to increase the temperature of the combustion chamber 17 and increase the proportion of alternative fuels in the mixed combustion.

In this embodiment, the water passage valve 301 has only been controlled to open or close, but it may also be controlled to open only a portion of the water passage valve when closed, reducing the flow rate of the cooling water to a small amount, thereby maintaining the cooling performance of the engine cylinder 13 as much as possible.

(Embodiment 4)
Next, a fourth embodiment will be described. The fourth embodiment will be described using a schematic diagram of an intake/exhaust system and a cooling system of a marine engine in Fig. 11 and a sub-control flowchart in Fig. 12. The fourth embodiment is similar to the other embodiments, and other configurations are similar to those of the first embodiment, so the same reference numerals will be used and the description thereof will be omitted.

In this fourth embodiment, the temperature of the combustion chamber 17 is changed by improving the intake and exhaust system of the engine 1.

Specifically, as shown in Figure 11, an air exhaust valve 401 that discharges part of the air in the intake system to the outside is provided in the intake/exhaust system AL path, and a bypass valve 402 that bypasses the exhaust gas from the turbocharger 101 is provided.

The control of this embodiment is performed according to the sub-control flowchart of FIG. 12. That is, the operation of the combustion chamber temperature increasing means, which corresponds to S4 in the main control flowchart of FIG. 5, is performed according to the control flow for the operation of the combustion chamber temperature increasing means (4) in FIG. 12(a), and the stopping of the combustion chamber temperature increasing means, which corresponds to S6 in the main control flowchart of FIG. 5, is performed according to the control flow for the stopping of the combustion chamber temperature increasing means (4) in FIG. 12(b). Note that "combustion chamber temperature increasing means (4)" is also referred to as the combustion chamber temperature increasing means of embodiment 4.

When the combustion chamber temperature increasing means (4) is activated, the air exhaust valve 401, which discharges a portion of the compressed air, is opened in S41. Next, the bypass valve 402, which bypasses the exhaust gas from the turbocharger 101, is opened in S42.

By opening the air exhaust valve 401 in this way, the amount of compressed air supplied to the combustion chamber 17 is reduced. On the other hand, by opening the bypass valve 402, the rotation speed of the turbocharger 101 is reduced, and the amount of compressed air supplied to the combustion chamber 17 is reduced. In this way, in both cases, the temperature of the combustion chamber 17 can be increased by reducing the amount of compressed air supplied to the combustion chamber 17.

On the other hand, when the combustion chamber temperature increasing means (4) is stopped, the air exhaust valve 401, which discharges a portion of the compressed air, is closed in S43. Next, the bypass valve 402, which bypasses the exhaust gas from the turbocharger 101, is closed in S44.

In this way, by closing the air exhaust valve 401 and the bypass valve 402, the amount of compressed air supplied to the combustion chamber 17 does not decrease. As a result, the combustion chamber temperature does not increase.

Therefore, in this embodiment, as in the other embodiments, in dual-fuel combustion mode, the temperature of the combustion chamber 17 can be increased, thereby increasing the dual-fuel combustion ratio. In normal combustion mode, the temperature of the combustion chamber 17 is low, which suppresses the generation of nitrogen oxides (NOx) and improves exhaust gas performance.

In this embodiment, the air exhaust valve 401 and the bypass valve 402 are provided and controlled, but it is also possible to provide and control only one of them. Also, while only control to open or close has been described, it is also possible to open only part of the valve.

(Embodiment 5)
Next, a fifth embodiment will be described. The fifth embodiment will be described using the schematic diagram showing the configuration of a marine engine in Fig. 13, the system schematic diagram showing an exhaust valve device in Fig. 14, the operation flowchart of the exhaust valve device in Fig. 15, and the sub-control flowchart in Fig. 16. Since the fifth embodiment is similar to the other embodiments and other components are similar to those of the first embodiment, the same reference numerals will be used and the description thereof will be omitted.

In this fifth embodiment, the temperature of the combustion chamber 17 is changed by improving the opening and closing timing of the exhaust valve 18.

First, the exhaust valve device EX of the engine 1 will be explained using Figures 13 and 14.

As shown in FIG. 13 , the exhaust valve device EX of this embodiment includes an exhaust valve 18 that is located above the combustion chamber 17 and moves back and forth in the vertical direction, an upper valve train 501 that is provided above the exhaust valve 18 and moves the exhaust valve 18 back and forth in the vertical direction, a lower valve train 502 that is located near the fuel pump 41 and connected to the upper valve train 501 via an oil passage to provide a driving force to the upper valve train 501, and an air supply unit 503 that is connected to the upper valve train 501 and supplies air to the upper valve train 502.

As shown in FIG. 14, the lower valve train 502 is provided with a control valve 504 that controls the hydraulic pressure, and an accumulator 505 that applies operating pressure to the control valve 504 is connected to the control valve 504. An exhaust valve control unit 506 is electrically connected to the control valve 504, and a detector 507 that detects the engine crank angle, etc. is electrically connected to the exhaust valve control unit 506.

The exhaust valve device EX configured in this manner operates according to the exhaust valve device operation flowchart in Figure 15.

First, in S101, the detection unit 507 detects the engine crank angle. Next, in S102, the exhaust valve control unit 506 sends a valve open command at a predetermined timing.

Then, in S103, the control valve 504 opens and hydraulic pressure is transmitted from the accumulator 505 to the lower valve train 502. Then, in S104, the piston (not shown) of the lower valve train 502 operates and hydraulic pressure is transmitted to the upper valve train 501. Then, in S105, the upper valve train 501 is pushed by the hydraulic pressure, pressing the exhaust valve 108 downward and opening the exhaust valve 108.

Then, in S106, a valve close command is sent from the exhaust valve control unit 506 at a predetermined timing. Then, in S107, the control valve 504 closes, the hydraulic pressure from the accumulator unit 505 disappears, and the piston (not shown) of the lower valve train 502 returns.

As a result, in S108, the hydraulic pressure from the lower valve train 502 disappears, and the downward pressing force on the upper valve train 501 disappears. Then, in S109, the downward pressing force on the upper valve train 501 disappears, and air from the air supply unit 503 moves the exhaust valve 18 upward, causing it to close.

In this way, the exhaust valve device EX of this embodiment operates.

In this embodiment, the opening and closing timing of the exhaust valve 18 is improved based on this exhaust valve device EX. Specifically, this is done according to the sub-control flowchart in Figure 16.

That is, the operation of the combustion chamber temperature increasing means corresponding to S4 in the main control flowchart of FIG. 5 is performed by the control flow for the operation of the combustion chamber temperature increasing means (5) in FIG. 16(a), and the stopping of the combustion chamber temperature increasing means corresponding to S6 in the main control flowchart of FIG. 5 is performed by the control flow for the stopping of the combustion chamber temperature increasing means (5) in FIG. 16(b). Note that the "combustion chamber temperature increasing means (5)" is also referred to as the combustion chamber temperature increasing means of embodiment 5.

When the combustion chamber temperature increasing means (5) is activated, an early valve closing command is sent from the exhaust valve control unit 506 in S51, causing the exhaust valve 18 to close at the early timing. On the other hand, when the combustion chamber temperature increasing means (4) is deactivated, an early valve closing command is sent from the exhaust valve control unit 506 in S52, causing the exhaust valve 18 to close at the standard timing.

Note that here, early timing refers to timing that is earlier than standard timing, for example, timing that is advanced by 0 to 60 degrees. The reason there is such a range in the advance angle is because the timing changes depending on the engine's operating conditions.

By controlling in this way, when the engine 1 is operated in the dual combustion mode, the exhaust valve 1
This causes the exhaust valve 18 to close early, increasing the temperature of the combustion chamber 17. In other words, by closing the exhaust valve 18 early, the period during which the air supplied to the combustion chamber 17 is compressed by the piston 21 becomes longer in the next cycle, and as a result, the temperature of the combustion chamber 17 also increases.

On the other hand, when the engine 1 is operating in normal combustion mode, the exhaust valve 18 closes as usual, so the temperature in the combustion chamber 17 does not rise.

As described above, in this embodiment, the combustion chamber temperature increasing means (5) is an exhaust valve device EX that advances the closing timing of the exhaust valve 18.

This advances the closing timing of the exhaust valve 18, lengthening the period during which air is compressed by the piston 21 in the next cycle.

As a result, the period during which the air in the combustion chamber 17 is compressed becomes longer, which results in an increase in the temperature of the combustion chamber 17.

Therefore, by advancing the closing timing of the exhaust valve 18, the temperature of the combustion chamber 17 can be increased, providing a combustion chamber temperature increasing means without affecting the engine 1's cooling system, and also increasing the proportion of alternative fuels in the mixed combustion ratio.

(Embodiment 6)
Next, a sixth embodiment will be described. The sixth embodiment will be described using the schematic diagram of the marine engine in Figure 17 and the sub-control flowchart in Figure 18. The sixth embodiment is similar to the other embodiments, and other components are similar to those of the first embodiment, so the same reference numerals will be used and the description thereof will be omitted.

In this sixth embodiment, a so-called "hot bulb" is used to change the temperature of the combustion chamber 17. A "hot bulb" is a spherical shell-shaped ball made of cast iron that becomes a heat source when heated by engine combustion or external thermal power.

As shown in Figure 17, this embodiment has a hot bulb chamber 602 containing a hot bulb 601 located above the combustion chamber 17 of the engine 1. This hot bulb chamber 602 and the combustion chamber 17 are connected via a communication passage 603, and this communication passage 603 is provided with a hot bulb valve (not shown) that opens and closes the communication state. This hot bulb valve is electrically connected to a hot bulb valve control unit 604 that controls the opening and closing of the hot bulb valve.

The control of this embodiment is performed according to the sub-control flowchart of Figure 18. That is, the operation of the combustion chamber temperature increasing means, which corresponds to S4 in the main control flowchart of Figure 5, is performed according to the control flow for the operation of the combustion chamber temperature increasing means (6) in Figure 18(a), and the stopping of the combustion chamber temperature increasing means, which corresponds to S6 in the main control flowchart of Figure 5, is performed according to the control flow for the stopping of the combustion chamber temperature increasing means (6) in Figure 18(b). Note that "combustion chamber temperature increasing means (6)" is also referred to as the combustion chamber temperature increasing means of embodiment 6.

When the combustion chamber temperature increasing means (6) is activated, an open valve command is sent from the hot bulb valve control unit 604 in S61, causing the hot bulb valve (not shown) to open. In this way, when the hot bulb valve (not shown) opens, the hot bulb 601 present in the hot bulb chamber 602 functions as a heat source, which has the effect of raising the temperature of the combustion chamber 17.

On the other hand, when the combustion chamber temperature increasing means (6) is stopped, a valve close command is sent from the hot bulb valve control unit 604 in S62 to close the hot bulb valve. When the hot bulb valve is closed in this manner, the effect of the hot bulb 602 in the hot bulb chamber 602 does not reach the combustion chamber 17, so the temperature of the combustion chamber 17 does not change.

As described above, in this embodiment, the combustion chamber temperature increasing means (6) is a hot bulb valve control unit 604 that controls a hot bulb valve (not shown) provided in a communication passage 603 that connects the hot bulb chamber 602, in which the hot bulb 601, which serves as a heat source, is located, and the combustion chamber 17.

As a result, when the hot bulb valve control unit 604 opens the hot bulb valve, the hot air in the hot bulb chamber 602 heated by the hot bulb 601, which is the heat source, is transferred to the combustion chamber 17, heating the combustion chamber 17.

This reliably increases the temperature in the combustion chamber 17, allowing for a higher mixed combustion ratio of alternative fuels.

Therefore, the hot bulb 601, which serves as a heat source, can be used to reliably increase the temperature of the combustion chamber 17, thereby increasing the mixed combustion ratio, which is the proportion of alternative fuel.

(Other embodiments)
Various embodiments have been described above, but the present invention is not limited to these. Any embodiment in which the temperature of the combustion chamber in the dual-fuel combustion mode is higher than the temperature of the combustion chamber in the normal combustion mode is within the technical scope of the present invention.

Furthermore, the alternative fuel is not limited to ammonia, but can be any fuel that can be used as an alternative to petroleum, such as biofuel, methanol, or ethanol.

As described above, the present invention relates to a marine engine used on a ship. It is particularly useful in a marine engine that can burn alternative fuels such as ammonia together with conventional fossil fuels.

1... Marine engine 10... Cylinder 17... Combustion chamber 30... Fuel injection valve 92... Control unit 112... Bypass valve (Combustion chamber temperature increasing means (1))
113...Restriction valve (combustion chamber temperature increasing means (1))
201...Cooling valve (combustion chamber temperature increasing means (2))
301... Water passage valve (combustion chamber temperature increasing means (3))
401...Air exhaust valve (combustion chamber temperature increasing means (4))
402...Bypass valve (combustion chamber temperature increasing means (4))
EX... Exhaust valve device (combustion chamber temperature increasing means (5))
604...Hot bulb valve control unit (combustion chamber temperature increasing means (6))

Claims (7)

A marine engine used in a scene where a ship navigates in a sea area under high load and a scene where a ship navigates in a sea area under low load,
a combustion mode selection means for selecting a mixed combustion mode in which both the alternative fuel and the fossil fuel are injected into the combustion chamber and burned, and a normal combustion mode in which the fossil fuel is injected into the combustion chamber and burned;
a combustion chamber temperature increasing means for increasing the temperature of the combustion chamber,
In a scene where the ship is sailing in a sea area under high load, the combustion mode selection means selects the dual combustion mode, and the combustion chamber temperature increasing means is operated to increase the temperature of the combustion chamber,
a marine engine comprising an engine control means that, when the ship is navigating an area of sea at a low load, selects the normal combustion mode with the combustion mode selection means and stops the combustion chamber temperature increasing means to control so as not to increase the temperature of the combustion chamber. 2. The marine engine according to claim 1, wherein the combustion chamber temperature increasing means is a scavenging air temperature increasing means for increasing the temperature of the scavenging air introduced into the combustion chamber. 3. The marine engine according to claim 2, wherein the scavenging air temperature increasing means is an air cooler cooling water flow rate limiting mechanism that limits the flow rate of cooling water in an air cooler that cools the scavenging air. 3. The marine engine according to claim 2, wherein the scavenging air temperature increasing means is an air cooler cooling water temperature increasing mechanism that increases the temperature of cooling water in an air cooler that cools the scavenging air. 2. The marine engine according to claim 1, wherein the combustion chamber temperature increasing means is an engine cylinder cooling water flow rate limiting mechanism that limits the flow rate of cooling water that cools the engine cylinder. 2. The marine engine according to claim 1, wherein the combustion chamber temperature increasing means is an exhaust valve advance mechanism that advances the closing timing of the exhaust valve. 2. A marine engine according to claim 1, wherein the combustion chamber temperature increasing means is a hot bulb communication mechanism that communicates the combustion chamber with a hot bulb chamber in which a hot bulb serving as a heat source is disposed.