JP7013529B2 - Large 2-stroke uniflow scavenging engine with gas fuel mode - Google Patents

Description

The present specification relates to a large two-stroke internal combustion engine having a gas fuel mode, and more particularly to a crosshead large two-stroke uniflow scavenging internal combustion engine having a gas fuel mode.

background

The crosshead type large 2-stroke uniflow scavenging internal combustion engine is used, for example, as a propulsion system for a large ship or as a prime mover for a power plant. The size of this large two-stroke engine is huge. This large two-stroke engine has a structure different from other internal combustion engines, not only because of its huge size.

Turbo supercharged large stroke uniflow scavenging internal combustion engines often use gas fuels such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG) instead of traditional marine diesel fuels and heavy oils. .. The reason for replacing gas fuels is primarily to reduce emissions and seek to provide eco-friendly prime movers.

Technological development towards the use of gas fuel has led to the development of two different types of turbocharged large two-stroke internal combustion engines that use gas fuel as the main fuel.

One of them is a direct injection type engine. In this type of engine, gas fuel is injected at high pressure near top dead center (TDC) and ignited by the high temperature generated by compression. That is, it ignites according to the diesel cycle. The gas fuel ignites the moment it is injected into the combustion chamber, and there is no concern about pre-ignition (premature ignition) due to the low excess air rate or misfire due to the high excess air rate. An efficient compression ratio for this first type turbocharged large 2-stroke uniflow scavenging internal combustion engine operated on gas fuel is the conventional turbocharged large 2-stroke uniflow scavenging internal combustion engine using liquid fuel. As high as the efficient compression ratio of, and even higher. Typically, the efficient compression ratio of this type of engine is from about 15 to about 17, while the geometric compression ratio is about 30. The advantage of the first type of engine described above is the very good fuel efficiency, which comes from the high compression ratio. Another advantage of the first type of engine described above is that it has a much lower risk of pre-ignition and misfire than the second type of engine described below.

However, in order to inject gas fuel near the TDC, the pressure of the gas fuel supplied to the fuel valve that injects the gas fuel into the combustion chamber must be much higher than the compression pressure of the combustion chamber. In fact, the gas fuel injected into the combustion chamber must have a pressure of at least 250 bar, preferably 300 bar. The pump station pressurizes the liquefied gas fuel to, for example, 300 bar, and then the high pressure liquefied fuel is vaporized by the high pressure vaporization unit and delivered to the fuel injection valve of the main engine in the form of high pressure gas. This supply system is more expensive than the conventional supply system for liquid fuels.

Gas fuels such as natural gas have a much lower energy density than conventional fuels. To be a useful energy source, the density must be increased. This is done by cooling the gas fuel to a very low temperature. For example, in the case of natural gas, it is made by using liquefied natural gas (LNG).

For this reason, gas fuel supply systems for engines operated on gas fuel include an insulating tank for storing liquefied gas. The adiabatic tank keeps the liquid state for a long time. However, the surrounding heat flux raises the temperature inside the tank, leading to vaporization of the liquefied gas. The gas resulting from this process is called Boil-Off Gas (BOG). Boil-off from the tank forms an practical steady flow of gas fuel. It must be removed from the tank and some action must be taken. For an 18000000 m3 LNG tanker, the amount of BOG that needs to be dealt with can reach several tons per hour. Typically about 3000 kg / hour. On the other hand, the gas required by the main engine of this type of LNG tanker is approximately 4000 kg / hour, assuming that the energy source of the main engine is all natural gas.

However, it is technically very difficult to pressurize the boil-off gas with a compressor to an injection pressure of about 300 bar. Therefore, the BOG cannot be used as a fuel for the above-mentioned first type turbocharged large two-stroke internal combustion engine.

BOG can also be pressurized to 10-20 bar using a compressor. It can then be used in gas fuel generators operated at this pressure. Ships often include a set of such generators in addition to a turbocharged large two-stroke internal combustion engine. Such generators are often 4-stroke internal combustion engines, which are much smaller than turbo-supercharged large 2-stroke internal combustion engines, and drive generators and alternators that generate electricity and heat used in ships.

The BOG can also be reliquefied in a cryogenerator. However, reliquefaction requires expensive equipment and consumes a considerable amount of energy.

Also, in an emergency, the BOG simply burns.

WO2016058611A1 discloses a first type large two stroke uniflow scavenging turbocharged internal combustion engine.

The second type of engine is called a low pressure gas engine. In this type of engine, gas fuel is mixed with scavenging. The second type of engine compresses the mixture of gas fuel and scavenging in the combustion chamber. In the second type of engine, gas fuel is introduced from a fuel valve provided in the middle of the cylinder liner. Fuel is introduced during the compression stroke of the piston from bottom dead center (BDC) to top dead center (TDC), well before the fuel valve closes. The piston compresses the air-fuel mixture of gas fuel and scavenging air in the combustion chamber, and the compressed air-fuel mixture is ignited in the vicinity of the TDC by means for igniting at the right time (for example, by injecting pilot oil or the like). The advantage of this type of engine is that it can be operated with gas fuel supplied at a relatively low pressure (eg about 15 bar) because the pressure in the combustion chamber when the gas fuel is injected Therefore, the second type of engine can be operated by the BOG boosted by the boosting means. Therefore, the gas supply system for the second type of engine. Is cheaper than the gas supply system for the first type of engine. In the case of the first type of engine, the BOG flow from the tank must be processed, and the set of boilers and generators Only part of this BOG stream can be used. Therefore, a relatively expensive reliquefaction system must be introduced and operated in the gas supply system of the first type of engine.

However, since the second type engine compresses the air-fuel mixture in the combustion chamber, the effective compression ratio is considerably lower than that of the first type engine. Typically, the effective compression ratio of the first type engine is between about 15 and about 17. In contrast, the effective compression ratio of the second type engine is between about 7 and about 9. The geometric compression ratio of the second type engine is about 13.5. This very low, geometrically defined compression ratio significantly reduces the fuel efficiency of the second type engine relative to the first type engine, compared to the first type engine of the same size. This is the cause of the low maximum continuous rotation speed of the second type engine.

In addition, the second type of engine usually requires a prechamber or synchronous ignition system to achieve reliable ignition.

A further disadvantage of the second type of engine is that the excess air ratio and bulk temperature during the compression stroke of the piston must be controlled very accurately. This is to prevent pre-ignition due to (local) too low air excess and / or too high bulk temperature, and to prevent misfire due to too high air excess and / or too low bulk temperature. Proper mixing that results in a uniform mixture is very important for the local conditions in the combustion chamber that result in pre-ignition and misfire. Controlling these conditions in the combustion chamber is particularly difficult in transient operation.

DK201770703 discloses a second type large two-stroke uniflow scavenging turbocharged internal combustion engine.

WO2014 / 0971763 is a fuel injection valve for injecting vaporized gas fuel at high pressure in or near the TDC to all cylinders, and a fuel for introducing boil-off gas in the middle of the stroke from the TBC to the TDC by the piston. It discloses a large 2-stroke engine equipped with an injection valve. This engine combines a first type and a second type engine. The object described in WO2014 / 0971763 is to avoid diesel knock (premature combustion). The purpose of this is to obtain the desired output level by introducing an amount of boil-off gas lower than the knocking threshold, to inject the vaporized gas fuel at high pressure in or near the TDC, and to set the desired output. This is achieved by injecting additional energy to obtain the desired output. However, this engine requires a fairly complex and expensive fuel supply system.

Description

It is an object of the present invention to provide an engine and gas fuel supply system, and a method that solves or at least alleviates the above-mentioned problems.

The above-mentioned objectives and other objectives are achieved by the characteristics described in the independent claims. More specific implementations will be clarified from the dependent claims, detailed description of the invention, and drawings.

According to the first aspect, a large two-stroke turbocharged uniflow scavenging internal combustion engine is provided as follows.
The engine has a plurality of combustion chambers, the plurality of combustion chambers forming the entire group of combustion chambers. Each combustion chamber belonging to all the groups is defined by a cylinder liner, a piston and a cylinder cover. The piston reciprocates between the BDC and the TDC. The combustion chambers belonging to all the groups include a combustion chamber belonging to the first subgroup and a combustion chamber belonging to the second subgroup, and each combustion chamber belonging to the all groups is the first subgroup. Or belongs to any of the above-mentioned second subgroups. The engine operates on gas fuel as the main fuel in at least one mode of operation.
The cylinders of the combustion chamber belonging to the first subgroup are
-A fuel introduction valve for introducing pressurized gas fuel into the combustion chamber during the stroke of the piston from BDC to TDC.
A fuel injection valve for injecting high pressure gas fuel into the combustion chamber when the piston is at or near the TDC.
Equip both.
The cylinders of the combustion chamber belonging to the second subgroup are
-A fuel introduction valve for introducing pressurized gas fuel into the combustion chamber during the stroke of the piston from BDC to TDC.
A fuel injection valve for injecting high pressure gas fuel into the combustion chamber when the piston is at or near the TDC.
Equip one of them.

By equipping only the cylinders of the selected subgroup with both a fuel introduction valve and a fuel injection valve, an engine that can operate with both low pressure gas for fuel introduction and high pressure gas for fuel injection is realized. At the same time, it is possible to greatly reduce the cost of the fuel supply system.

An engine in which all cylinders are equipped with a fuel injection valve and a small number of cylinders are equipped with both a fuel injection valve and a fuel introduction valve can consume boil-off gas from a liquefied fuel gas tank by the fuel injection valve. .. Therefore, it is not necessary to separately prepare a device for consuming the boil-off gas in a useful form.

Engines equipped with a fuel introduction valve on all cylinders and both a fuel introduction valve and a fuel injection valve on only a few cylinders may consume boil-off gas from the liquefied fuel gas tank by the fuel introduction valve . can. Then, the cylinder equipped with both the fuel introduction valve and the fuel injection valve can be operated at a high output setting. This is because the total amount of gas fuel supplied to these cylinders is not limited by knocking or premature combustion thresholds.

In an example of the mounting form of the first aspect,
The engine refers to the combustion chambers belonging to the first subgroup in at least one mode of operation.
During the stroke of the piston from the BDC to the TDC, a first amount of pressurized gas fuel is introduced into the combustion chamber by the fuel introduction valve;
A second amount of high pressure gas fuel is injected into the combustion chamber by the fuel injection valve when the piston is at or near the TDC;
It is configured as follows.

In one example of the implementation of the first aspect, the engine has a fuel supply system comprising a fuel tank for liquefied fuel gas, the fuel tank producing a boil-off gas flow. The fuel supply system is configured to supply pressurized boil-off fuel gas from the fuel tank to the fuel introduction valve, and vaporizes the high-pressure liquefied gas fuel from the fuel tank to provide high-pressure vaporized fuel. It is configured to supply to the fuel injection valve.

In an example of the mounting embodiment of the first aspect, the cylinder belonging to the second subgroup is equipped with a fuel injection valve and the engine is configured to consume most or all of the boil-off gas flow.

In an example of the mounting embodiment of the first aspect, the cylinder belonging to the second subgroup is equipped with a fuel injection valve, and the fuel system vaporizes a main part of the liquefied gas fuel at a low pressure to vaporize the fuel. It is configured to supply to the introduction valve, vaporize the non-major portion of the liquefied gas fuel at high pressure, and supply it to the fuel injection valve.

In an example of the mounting embodiment of the first side surface, the fuel introduction valve is arranged in a cylinder liner, and the fuel injection valve is arranged in a cylinder cover.

In an example of the mounting embodiment of the first aspect, the engine is a scavenging port for introducing scavenging into the combustion chamber, and has a scavenging port arranged in the cylinder liner and controlled by a piston. May be good. The engine may also have an exhaust outlet located on the cylinder cover and controlled by an exhaust valve.

In one example of the implementation of the first aspect, the engine introduces the first amount of pressurized gas fuel and injects the second amount of high pressure gas fuel in a single engine cycle. It is composed of.

In an example of the mounting embodiment of the first aspect, the engine is after the introduction of the first amount of pressurized gas fuel and before or before the injection of the second amount of high pressure gas fuel. The second amount of high pressure gas fuel is injected and at the same time a third amount of ignition liquid is introduced.

In an example of the implementation of the first aspect, the first pressure P1, which is the pressure at which the vaporized fuel is delivered to the fuel injection valve, is a pressure exceeding 150 Bar.

In an example of the implementation of the first aspect, the second pressure P2, which is the pressure at which the boil-off gas is delivered to the fuel introduction valve, is a pressure between 5 Bar and 40 Bar, preferably between 10 Bar and 20 Ba. Pressure.

In an example of the mounting embodiment of the first aspect, the first amount of gas fuel accounts for 20-80% of the total amount of fuel supplied to the combustion chamber during one engine cycle, said second. The amount of gas fuel accounts for 20-80% of the total amount of fuel supplied to the combustion chamber during a single engine cycle. Preferably, the first amount of gas fuel accounts for 30-70% of the total amount of fuel supplied to the combustion chamber during one engine cycle, and the second amount of gas fuel is once. It accounts for 30-70% of the total fuel supplied to the combustion chamber during the engine cycle.

In an example of the implementation of the first aspect, the third amount of ignition liquid is greater than 5% of the calorie value of all fuels supplied to the at least one combustion chamber during a given engine cycle. Few. Preferably less than 3%.

In an example of the implementation of the first aspect, the engine comprises at least one controller. The controller is connected to the fuel introduction valve and the fuel injection valve to control the fuel introduction valve and the fuel injection valve. The controller is attached to the fuel introduction valve and the fuel injection valve.
Introducing a first amount of boil-off gas fuel into the combustion chamber belonging to the first subgroup during the stroke of the piston from the BDC to the TDC, and
Injecting a second amount of high pressure vaporized gas fuel into the combustion chamber belonging to the first subgroup when the piston is at or near the TDC;
Is configured to carry out.

In an example of the mounting embodiment of the first aspect, the engine comprises a low load operating mode. At this time, the engine introduces the first amount of gas fuel from the second source into the at least one combustion chamber during the stroke of the piston from the BDC to the TDC, but the piston is the TDC or It is configured not to inject the second amount of gas fuel from the first source into the at least one combustion chamber when it is in the vicinity.

In an example of the mounting embodiment of the first aspect, the engine comprises a high load operating mode. At this time, the engine injects the second amount of gas fuel from the first source into the at least one combustion chamber when the piston is at or near the TDC, while the piston is from the BDC to the TDC. During the stroke towards, the first amount of gas fuel is configured not to be introduced into the at least one combustion chamber from the second source.

These and other aspects will be further clarified by the examples described below.

Hereinafter, various aspects, embodiments, and implementation examples will be described in detail with reference to the exemplary embodiments shown in the drawings.
FIG. 3 is a front view of a large two-stroke engine according to an exemplary embodiment. It is a side view of the large two-stroke engine of FIG. It is a schematic representation of the large two-stroke engine of FIG. It is sectional drawing of the cylinder frame and the cylinder liner of the engine of FIG. Cylinder covers and exhaust valves are attached and pistons in TDC and BDC are also depicted. It is a graph depicting a gas exchange and a fuel injection cycle. FIG. 3 is a cross-sectional view of a cylinder frame and cylinder liner according to another embodiment. It is a schematic representation of a large two-stroke engine according to the first embodiment. It is a schematic representation of a large two-stroke engine according to the first embodiment.

Detailed explanation

In the following detailed description, the internal combustion engine will be described with reference to an example of a crosshead type large low speed 2-stroke turbocharged internal combustion engine. 1 to 3 show an example of a turbocharged large low-speed 2-stroke internal combustion engine. This engine has a crankshaft 8 and a crosshead 9. 1 is a front view and FIG. 2 is a side view. FIG. 3 is a schematic representation of the turbocharged large low-speed 2-stroke diesel engine of FIGS. 1 and 2 together with its intake system and exhaust system. In this example, the engine has four cylinders in series. A turbocharged large low speed 2-stroke internal combustion engine typically has 4 to 14 cylinders arranged in series. These cylinders are supported on the engine frame 11. Further, such an engine can be used, for example, as a main engine of a ship or a fixed engine for operating a generator in a power plant. The total output of the engine can be, for example, 1,000 kW to 110,000 kW.

The engine combines a diesel cycle and an Otto cycle in an operating mode in which the first subgroup of cylinders operates on gas fuel as the main fuel. This is because the cylinder involved in this combination is a compression ignition, but compresses a mixture of air and fuel. This fuel is a first amount of pressurized gas fuel introduced in the middle of the compression stroke of the piston. The compressed air fuel mixture is ignited when a second amount of high pressure gas fuel is injected near the TDC.

The engine can operate the cylinders of the first subgroup according to the diesel cycle in another mode of operation. In this mode, no fuel is introduced during the compression stroke. In this mode, all fuel is injected near the TDC. The main fuel in this mode can also be gas fuel. In yet another mode of operation, the engine can operate the cylinders of the first subgroup according to the Otto cycle. In this case, all gas fuels are mixed in the scavenging and the air-fuel mixture is compressed during the compression stroke. Then, in the vicinity of the TDC, a means for igniting at the right timing is provided.

The engine in this embodiment is a two-stroke uniflow scavenging engine, in which a scavenging port 18 is provided in the lower region of the cylinder liner 1, and an exhaust valve 4 is arranged in the center of the top of the cylinder liner 1. The combustion chamber is defined by a cylinder liner 1, a cylinder cover 22, and a piston 10 that reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner.

The scavenging is guided from the scavenging receiver 2 to the scavenging port 18 at the lower end of each cylinder 1 when the piston is below the scavenging port 18. The gas fuel is introduced from the gas fuel introduction valve 30 under the control of the electronic control unit 60. This is done during the ascending stroke of the piston, before the piston passes through the fuel valve (gas fuel introduction valve) 30. The cylinder 1 on which the fuel valve 30 is mounted is preferably equipped with a plurality of fuel valves 30. These fuel valves are preferably arranged so as to be evenly spaced over the circumference of the cylinder liner. Further, it is preferably arranged near the center in the longitudinal direction of the cylinder liner. The introduction of gas fuel is carried out when the compression pressure is relatively low. That is, it is performed when the compression pressure when the piston 10 reaches TDC is much lower than the compression pressure.

Within the cylinder liner 1, the piston 10 compresses a mixture of gas fuel and scavenging air. Then, high-pressure gas fuel is injected from the fuel injection valve 50 at or near the TDC. Ignition is triggered according to the principle of diesel by the high temperature caused by the high pressure in the combustion chamber at or near the TDC. Ignition may be assisted by a small amount of pilot oil (or suitable ignition liquid). In some cases, this pilot oil is injected from the fuel injection valve 50 together with the gas fuel, but in other cases, it is configured to be supplied from a dedicated pilot oil valve (not shown). .. In that case, it is preferable that the pilot oil valve 51 is arranged on the cylinder cover 22 in all the cylinders.

Note that "TDC or its vicinity" and "TDC or its vicinity" mean that gas fuel is injected. Refers to a range. This range begins at about 15 degrees before TDC at the earliest and ends at about 40 degrees after TDC at the latest.

Combustion occurs and exhaust gas is produced. In other forms of ignition systems, instead of or in addition to pilot oil, prechambers, laser ignitions, glow plugs (none of which are shown), etc. may be used to facilitate ignition.

When the exhaust valve 4 is opened, the exhaust gas flows to the exhaust receiver 3 through the exhaust duct provided in the cylinder 1, and further advances to the turbine 6 of the turbocharger 5 through the first exhaust pipe 19. From there, the exhaust gas flows to the economizer 20 through the second exhaust pipe 25, and is further discharged into the atmosphere from the outlet 21. The turbine 6 drives the compressor 7 via a shaft. Outside air is supplied to the compressor 9 through the air intake port 12. The compressor 7 sends the compressed scavenging air to the scavenging pipe 13 connected to the scavenging receiver 2. The scavenging of the pipe 13 passes through the intercooler 14 for cooling the scavenging.

The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging airflow when the compressor 7 of the turbocharger 5 is unable to supply the pressure required for the scavenging receiver 2, that is, when the engine is under low or partial load. If the engine load is high, the turbocharger compressor 7 can supply a fully compressed scavenger so that the auxiliary blower 16 is bypassed by the check valve 15.

FIG. 3 shows a controller 60 such as an electronic control unit. The controller 60 is connected to various sensors through signal lines or other communication channels, and these sensors convey information about the operating conditions of the engine to the controller 60. The controller 60 is also connected to various engine components controlled by the controller 60 through signal lines or other communication channels. One of the above sensors is a crank angle sensor, which is illustrated. This transmits the rotation angle of the crankshaft 8 to the controller 60. The controller 60 controls the fuel introduction valve 30, the fuel injection valve 50, and preferably the exhaust valve 4.

The controller 60 is connected to the fuel introduction valve 30 and the fuel injection valve 50 and controls them. The controller 60 operates the fuel introduction valve 30 for the cylinders of the first group, from the second source 40 of the pressurized gas fuel to the combustion chamber during the stroke of the piston 10 from the BDC to the TDC. It is configured to introduce a first amount of gas fuel. The controller 60 also operates the fuel injection valve 50 for the cylinders of the first group, from the first source 35 of the pressurized gas fuel to the combustion chamber when the piston 10 is at or near top dead center. It is configured to inject a second amount of gas fuel into at least one.

The cylinder 1 of the second subgroup is equipped with either a fuel introduction valve 30 or a fuel injection valve 50. The cylinder 1 of this engine belongs to either the first subgroup or the second subgroup.

FIG. 4 shows the cylinder 1 of the first subgroup. Depending on the size of the engine, the cylinder liner 1 can be made in various sizes. This is the same for the cylinders of the first subgroup and the second subgroup. Typical sizes are 250 mm to 1000 mm in diameter and the corresponding overall length is 1000 mm to 4500 mm.

FIG. 4 shows that the cylinder liner 1 is mounted on the cylinder frame 23 and the cylinder cover 22 is mounted on the cylinder liner 1. The cylinder liner 1 and the cylinder cover 22 are connected so that gas does not leak from between the cylinder liner 1 and the cylinder cover 22.

In FIG. 4, the state of the piston 10 at the bottom dead center (BDC) and the top dead center (TDC) is shown by a broken line. Of course, these two states do not occur at the same time, and these two states are separated by 180 degrees by the rotation angle of the crankshaft 8. The cylinder liner 1 is provided with a cylinder lubrication hole 25 and a cylinder lubrication line 24. These supply cylinder lubricating oil as the piston 10 passes through the lubrication line 24. Subsequently, a piston ring (not shown) spreads the cylinder lubricant over the running surface of the cylinder liner.

The fuel valve 50 is mounted on the cylinder cover 22. Usually, in each cylinder, two or three fuel injection valves 50 are distributed around the exhaust valves at the same spacing. The fuel injection valve 50 is connected to the first source 35 of the high pressure gas fuel through the first supply pipe 36, and is connected to the pilot oil source 27 through the pilot line 28.

The third amount of igniter is less than 5% of the caloric value of all fuels put into the combustion chamber during a given engine cycle. Preferably less than 3%.

The fuel valve 50 may be of the type disclosed in DK178519B1. This type of fuel valve has the ability to inject a small amount of pilot oil into the combustion chamber, along with a sufficient amount of high pressure gas fuel.

The injection timing of the high-pressure gas fuel and the pilot oil by the fuel injection valve 50 is controlled by the electronic control unit 60. The electronic control unit 60 is connected to the fuel valve 50 through the signal line shown by the broken line in FIG.

The cylinder liner 1 is equipped with a fuel introduction valve 30. The fuel introduction valve 30 has a nozzle or an introduction port located substantially on the same surface as the inner surface of the cylinder liner 1. Further, the rear end of the fuel introduction valve 30 protrudes from the outer wall of the cylinder liner 1. Typically, one or two, at most three or four fuel introduction valves 30, are provided in each cylinder liner 1. These are arranged at equal intervals in the circumferential region of the cylinder liner 1. In this embodiment, the fuel introduction valve 30 is arranged exactly at the center of the cylinder liner 1 in the longitudinal direction.

The injection timing of the pressurized gas fuel by the fuel injection valve 30 is controlled by the electronic control unit 60. In FIG. 3, the electronic control unit 60 is connected to the fuel introduction valve 30 through a conceptually shown signal line.

For the cylinders of the first subgroup, the engine introduces a first amount of pressurized gas fuel and injects a second amount of high pressure gas fuel during one engine cycle. It is composed of. First, a first amount of pressurized gas fuel is introduced, followed by a second amount of high pressure gas fuel, which is injected at the opportunity for the piston to approach the TDC (this may be referred to as the first opportunity).

FIG. 4 is a conceptual and simplified drawing of the engine's gas fuel supply system. A first source 35 of high-pressure gas fuel is connected to each fuel injection valve 50 of the cylinder cover 22 through a first supply pipe 36. Further, a second source 40 of the medium pressure gas fuel is connected to the inlet of the gas fuel valve 30 through the boil-off gas supply pipe 41.

In this embodiment, the pressure P1 of the first source 35 of the high pressure gas fuel is approximately 15 to 45 MPa (150 to 450 bar). This high pressure makes it possible to inject gas fuel against peak pressures near the TDC.

In this embodiment, the pressure P2 of the second source 40 of the medium pressure gas fuel is approximately 1 to 3 MPa (10 to 30 bar). The pressure is medium compared to P1. However, with this pressure, gas fuel can be introduced during the compression stroke.

The cylinder 1 of the second subgroup is basically the same as the cylinder of the first subgroup, except that it is equipped with only one of the fuel injection valve 50 and the fuel introduction valve 30.

FIG. 5 shows the scavenging port 18, the exhaust valve 4, the fuel introduction valve (GA fuel valve) 30, and the fuel injection valve (Gi) as a function of the crank angle (angle of the crankshaft 8) for the cylinders of the first subgroup. The valve opening (opening) period and the valve closing (closing) period of each of the fuel valves) are illustrated. Looking at this graph, we can see that the window for introducing gas fuel is relatively short. Therefore, the time for mixing the gas fuel with scavenging in the combustion chamber is extremely short. Gas fuel is introduced during a very short window. High pressure gas fuel is injected between the windows near the TDC.

For the cylinders of the first subgroup, the total amount of gas fuel introduced and injected during one revolution is affected by the engine load. The total amount of gas fuel charged into the combustion chamber is the total amount of the first amount of gas fuel introduced into the cylinder at pressure P2 and the high-pressure gas fuel injected into the cylinder at pressure P2. In one embodiment, approximately 70% or 80% of the gas fuel charged into the cylinders of the first subgroup is gas introduced at pressure P2 from the second source 40 of the pressurized gas fuel. It is a fuel. In one embodiment, approximately 70% or 80% of the gas fuel charged into the cylinders of the first subgroup is injected at pressure P1 from the first source 35 of the high pressure gas fuel. Is.

In this way, the ratio of the first amount to the second amount can be adjusted and adapted to the amount of fuel available from each source. For example, if the high pressure fuel available from the first source 35 of the high pressure gas fuel is relatively low, the engine will have a medium pressure introduced into the cylinder during the compression stroke from the second source 40 of the pressurized gas fuel. It can be operated by using a large amount of gas fuel and using a relatively small amount of high-pressure gas fuel injected at or near the TDC. On the other hand, when the medium pressure gas fuel available from the second source 40 of the pressurized gas fuel is relatively small, the engine uses a large amount of the high pressure gas fuel injected at or near the TDC, and the pressurized gas fuel is the first. It can be operated with less fuel introduced into the cylinder during the compression stroke from the source 40 of 2.

FIG. 6 shows another embodiment of the cylinder 1 of the first subgroup. In the embodiment of FIG. 6, the same or corresponding configurations and features as those already described or illustrated are designated by the same reference numerals as those previously used. The main difference of this embodiment as compared with the embodiment of FIG. 4 is that the gas fuel introduction valve 30 is mounted on the cylinder cover 22. In this embodiment, all of the fuel valves 30 and 50 are arranged on the cylinder cover 22.

A plurality of cylinders 1 are mounted on the engine in this embodiment, and all of them form an entire group. Both the fuel injection valve 50 and the fuel introduction valve 30 are provided for only one cylinder 1 included in the entire group or for a plurality of selected cylinders. These cylinders 1 form a first subgroup. The remaining cylinders form a second subgroup. In the first variation of this embodiment, the cylinders included in the second subgroup are equipped with only the fuel introduction valve 30. In the second variation of this embodiment, the cylinders included in the second subgroup are equipped with only the fuel injection valve 50.

FIG. 7 is a schematic representation of the engine according to the second variation. In the embodiment of FIG. 7, the same or corresponding configurations and features as those already described or illustrated are designated by the same reference numerals as those previously used. The engine of the embodiment of FIG. 7 is a large two-stroke turbocharged uniflow scavenging internal combustion engine as in the above embodiment. FIG. 7 is an illustration focusing mainly on the cylinder 1 and the fuel supply system. This engine can be a dual engine. That is, although not shown, it may have a fuel supply system for using traditional fuels such as fuel oil, whereby the engine is operated with the traditional fuel instead of gas fuel. It may be possible. In some embodiments, the engine and fuel system may be mounted as the main engine of a ship.

At least a part of the fuel tank 26 is filled with liquefied gas fuel. The boil-off gas from the fuel tank 26 is sent to the compressor unit 46 through the boil-off gas supply pipe 42, and the pressure thereof is raised to a pressure suitable for introduction into the cylinder 1. The cylinders of the first subgroup are equipped with a fuel introduction valve 30. From the compressor unit 46, the pressurized boil-off gas is delivered to the fuel introduction valve 30 through the boil-off gas supply pipe 41. This boil-off gas is introduced by the fuel introduction valve 30 into the cylinder 1 (of the first subgroup) in the middle of the stroke of the piston from the BDC to the TDC.

In the illustrated embodiment, the engine is equipped with six cylinders 1. However, depending on the embodiment, the engine may be equipped with 4 to 16 cylinders. In the illustrated embodiment, only two of the six cylinders are equipped with a fuel introduction valve 30 for introducing boil-off gas. That is, the fuel introduction valve 30 is equipped only in a part of the total number of cylinders, for example, only a small part of the whole number. This small number of cylinders constitutes the first subgroup. In some embodiments, one to about half of the cylinders are equipped with a fuel introduction valve 30. That is, one to about half of the cylinders make up the first subgroup.

All the cylinders 1 of this implementation are equipped with a fuel introduction valve 50. The fuel injection valve 50 is supplied with high-pressure vaporized gas fuel made from the fuel that was liquid in the fuel tank 26. The liquefied gas fuel is sent from the fuel tank 26 to the fuel pump 37 through the feed pipe 31, is pressurized in the form of a liquid, and is subsequently vaporized by the high pressure vaporizer 38. The vaporized high-pressure gas fuel is supplied from the high-pressure vaporizer 38 to the fuel injection valve 50 through the first supply pipe 36. This high-pressure vaporized gas fuel is injected from the fuel injection valve 50 into the cylinder 1 when the piston 10 is at or near the TDC.

In this embodiment, the cylinder 1 equipped with only the fuel injection valve 50 forms the second subgroup. In FIG. 7, the engine is drawn to have two cylinders 1 belonging to the first subgroup and four cylinders belonging to the second subgroup. However, depending on the embodiment, the number of cylinders in the first subgroup and the number of cylinders in the second subgroup can be arbitrarily selected. Preferably, the cylinder 1 of the first subgroup is a small number of the whole. That is, the number of cylinders 1 in the first subgroup is smaller than the number of cylinders 1 in the second subgroup.

The number of cylinders in the first subgroup can be selected so that all boil-off gas from the fuel tank 26 is consumed by introduction into the cylinders.

FIG. 8 is a schematic representation of an engine according to the first variation previously described. In the embodiment of FIG. 8, the same or corresponding configurations and features as those already described or illustrated are designated by the same reference numerals as those previously used. The engine of the embodiment of FIG. 8 is a large two-stroke turbocharged uniflow scavenging internal combustion engine as in the above embodiment. FIG. 8 is an illustration focusing mainly on the cylinder 1 and the fuel supply system. This engine can be a dual engine. That is, although not shown, it may have a fuel supply system for using traditional fuels such as fuel oil, whereby the engine is operated with the traditional fuel instead of gas fuel. It may be possible. In some embodiments, the engine and fuel system may be mounted as the main engine of a ship.

At least a part of the fuel tank 26 is filled with liquefied gas fuel. The boil-off gas from the fuel tank 26 is sent to the compressor unit 46 through the boil-off gas supply pipe 42, and the pressure thereof is raised to a pressure suitable for introduction into the cylinder 1. From the compressor unit 46, the pressurized boil-off gas is delivered to the fuel introduction valve 30 through the boil-off gas supply pipe 41. Since the fuel introduction valve 30 is installed in both the cylinders of the first subgroup and the cylinders of the second subgroup, the pressurized boil-off gas is introduced into all the cylinders 1. The boil-off gas is introduced into the cylinder 1 in the middle of the stroke from the BDC to the TDC of the piston.

In the illustrated embodiment, the engine is equipped with six cylinders 1. However, depending on the embodiment, the engine may be equipped with 4 to 16 cylinders. In the illustrated embodiment, only two of the six cylinders are equipped with a fuel injection valve 50 that injects vaporized gas fuel into the cylinders. That is, the fuel injection valve 50 is equipped only in a part of the total number of cylinders, for example, only a small part of the whole number. This small number of cylinders constitutes the first subgroup. In some embodiments, one to about half of the cylinders are equipped with a fuel injection valve 50. That is, one to about half of the cylinders make up the first subgroup.

In this implementation, all cylinders 1 are equipped with fuel introduction valves 30 to receive pressurized boil-off gas as described above. The cylinders of the first subgroup are equipped with a fuel introduction valve 30 and a fuel injection valve 50.

The fuel injection valve 50 of the first subgroup is supplied with high pressure vaporized gas fuel made from the fuel that was liquid in the fuel tank 26. The liquefied gas fuel is sent from the fuel tank 26 to the fuel pump 37 through the feed pipe 31, is pressurized in the form of a liquid, and is subsequently vaporized by the high pressure vaporizer 38. The vaporized high-pressure gas fuel is supplied from the high-pressure vaporizer 38 to the fuel injection valve 50 through the first supply pipe 36. This high pressure vaporized gas fuel is injected from the fuel injection valve 50 into the cylinder 1 (in the first subgroup) when the piston 10 is at or near the TDC.

In this embodiment, the cylinder 1 equipped only with the fuel introduction valve 30 forms the second subgroup.

In FIG. 8, the engine is drawn to have two cylinders 1 belonging to the first subgroup and four cylinders belonging to the second subgroup. However, depending on the embodiment, the number of cylinders in the first subgroup and the number of cylinders in the second subgroup can be arbitrarily selected. Preferably, the cylinder 1 of the first subgroup is a small number of the whole. That is, the number of cylinders 1 in the first subgroup is smaller than the number of cylinders 1 in the second subgroup. An engine in which all cylinders 1 are equipped with a fuel introduction valve 30 and only a few cylinders 1 are equipped with both a fuel introduction valve 30 and a fuel injection valve 50 is a boil-off gas from a liquefied fuel gas tank through the fuel introduction valve 30. Can be consumed altogether. Then, the cylinder of the first subgroup equipped with both the fuel introduction valve 30 and the fuel injection valve 50 can be operated at a high output setting. This is because the total amount of gas fuel supplied to the cylinders of the first subgroup is not so limited by knocking or premature combustion.

Many aspects and implementations have been described with some examples. However, considering the specification, drawings, and claims of the present application, those skilled in the art have many variations in carrying out the inventions described in the claims in addition to the described examples. You will be able to understand and embody that. The terms "prepared", "have", and "include" described in the claims do not exclude the existence of elements or steps that are not described. Even if it is not explicitly stated that the number of elements described in the claims is multiple, it does not exclude the existence of multiple elements. The functions of some of the elements described in the claims may be performed by a single processor, controller, or other unit. Even if some matters are described in separate dependent claims, it is not excluded to carry out these in combination, and it is possible to make a profit by carrying out them in combination.

The reference numerals used in the claims shall not be construed as limiting the scope of the invention.

Claims (9)

A large 2-stroke turbocharged uniflow scavenging internal combustion engine
The engine has a plurality of combustion chambers, the plurality of combustion chambers form an entire group of combustion chambers, each combustion chamber belonging to the all groups is defined by a cylinder liner, a piston, a cylinder cover, and the piston Connected to the crankshaft by a crosshead, the piston reciprocates between the BDC and TDC.
The engine is a scavenging port for introducing scavenging into the combustion chamber, a scavenging port arranged in a cylinder liner and controlled by a piston, and a central exhaust discharge port arranged in a cylinder cover and controlled by an exhaust valve. And have
The combustion chambers belonging to all the groups include a combustion chamber belonging to the first subgroup and a combustion chamber belonging to the second subgroup, and each combustion chamber belonging to the all groups is the first subgroup. Or belongs to one of the second subgroups mentioned above,
The engine operates on gas fuel as the main fuel in at least one mode of operation.
The cylinders of the combustion chamber belonging to the first subgroup are
Two, three, or four fuel introduction valves arranged in the cylinder liner of the cylinder for introducing pressurized gas fuel into the combustion chamber during the stroke of the piston from the BDC to the TDC. Introductory valve and
Two or three fuel injection valves mounted on the cylinder cover of the cylinder and distributed around the central exhaust outlet of the cylinder, high pressure gas fuel when the piston is at or near the TDC. With a fuel injection valve for injecting fuel into the combustion chamber,
Equipped with both,
The cylinders of the combustion chamber belonging to the second subgroup are
Two, three, or four fuel introduction valves arranged in the cylinder liner of the cylinder for introducing pressurized gas fuel into the combustion chamber during the stroke of the piston from the BDC to the TDC. Introductory valve and
Two or three fuel injection valves mounted on the cylinder cover of the cylinder and distributed around the central exhaust outlet of the cylinder, high pressure gas fuel when the piston is at or near the TDC. With a fuel injection valve for injecting fuel into the combustion chamber,
An institution equipped with either. For combustion chambers belonging to the first subgroup in at least one mode of operation.
During the stroke of the piston from the BDC to the TDC, a first amount of pressurized gas fuel is introduced into the combustion chamber by the fuel introduction valve;
When the piston is at or near the TDC (50), a second amount of high pressure gas fuel is injected into the combustion chamber by the fuel injection valve;
The institution according to claim 1. Equipped with a fuel supply system with a fuel tank to store liquefied fuel gas,
The fuel tank is configured to generate a boil-off gas flow.
The fuel supply system is configured to supply pressurized boil-off fuel gas from the fuel tank to the fuel introduction valve, vaporize the high-pressure liquefied gas fuel from the fuel tank, and supply the high-pressure vaporized fuel. Configured to supply fuel injection valves,
The institution according to claim 1 or 2. The institution according to claim 3.
Cylinders belonging to the second subgroup are equipped with fuel injection valves.
The engine is configured to consume most or all of the boil-off gas flow by the fuel introduction valve of a cylinder belonging to the first subgroup.
institution. Cylinders belonging to the second subgroup are equipped with fuel introduction valves.
The fuel supply system vaporizes the main part of the liquefied gas fuel at low pressure and supplies it to the fuel introduction valve, and vaporizes the non-main part of the liquefied gas fuel at high pressure and supplies it to the fuel injection valve. Consists of,
The institution according to claim 3. The engine according to any one of claims 1 to 5, wherein the fuel introduction valve is arranged in a cylinder liner, and the fuel injection valve is arranged in a cylinder cover. The engine according to claim 1 , wherein in a single engine cycle, the first amount of pressurized gas fuel is introduced and the second amount of high pressure gas fuel is injected. The first amount of pressurized gas fuel accounts for 20-80% of the total fuel supplied to the combustion chamber during one engine cycle, and the second amount of high pressure gas fuel is once. It accounts for 20-80% of the total fuel supplied to the combustion chamber during the engine cycle of
Preferably, the first amount of pressurized gas fuel accounts for 30-70% of the total amount of fuel supplied to the combustion chamber during one engine cycle, and the second amount of high pressure gas fuel is , 30-70% of the total fuel supplied to the combustion chamber during a single engine cycle,
The institution according to claim 7 . The fuel introduction valve and the fuel injection valve are connected to and controlled by at least one controller, and the at least one controller is attached to the fuel introduction valve and the fuel injection valve.
Introducing a first amount of boil-off gas fuel into the combustion chamber belonging to the first subgroup during the stroke of the piston from the BDC to the TDC;
Injecting a second amount of high pressure vaporized gas fuel into the combustion chamber belonging to the first subgroup when the piston is at or near the TDC;
The institution according to any one of claims 1 to 8 , which is configured to carry out.

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