KR20220013430A - Internal combustion engine - Google Patents

Abstract

Disclosed is a two-stroke uniflow scavenging type crosshead internal combustion engine. The engine comprises at least one cylinder, a cylinder cover, a piston, a fuel gas supply system, and a scavenging air system. The cylinder has a cylinder wall. The cylinder cover is disposed on top of the cylinder and has an exhaust valve. The fuel gas supply system includes a fuel gas valve configured to inject fuel gas into the cylinder during a compression stroke so as to enable the fuel gas to be mixed with scavenging air. The engine further includes a pre-chamber and a pilot fuel supply system. The pilot fuel supply system includes a pilot fuel valve configured to inject a pilot fuel gas into the pre-chamber during a compression stroke so as to enable the pilot fuel gas to be compressed before being ignited, and an ignition element is configured to ignite the pilot fuel gas in the pre-chamber. According to the present invention, the safety of the internal combustion engine can be enhanced.

Description

internal combustion engine {INTERNAL COMBUSTION ENGINE}

The present invention relates to a two-stroke uniflow scavenging crosshead internal combustion engine and a pre-chamber.

Two-stroke internal combustion engines are used as propulsion engines in ships such as container ships, bulk carriers, and oil tankers. It is becoming increasingly important to reduce unwanted exhaust gases from internal combustion engines.

One effective way to reduce the amount of unwanted exhaust gases is the conversion of fuel oils such as heavy fuel oil (HFO) to fuel gas. The fuel gas may be injected into the cylinder at the end of the compression stroke, where it may be ignited immediately by the high temperature the gas in the cylinder reaches during compression or by ignition of the pilot fuel. However, injecting fuel gas into the cylinder at the end of the compression stroke requires a high-pressure gas compressor to compress the fuel gas prior to injection to overcome the high pressure in the cylinder.

However, high pressure gas compressors are expensive and complex to manufacture and maintain. One way to avoid the use of a high pressure compressor is to configure the engine to inject fuel gas at the beginning of the compression stroke where the pressure in the cylinder is significantly lower.

Patent document WO 2013/007863 discloses such an engine. A pilot ignition pre-chamber is provided in the cylinder cover to ensure proper ignition of the fuel gas. A predetermined amount of pilot fuel oil is injected into the pilot ignition pre-chamber, and then self-ignitions due to the temperature and pressure in the pilot ignition pre-chamber. This causes a spark that ignites the fuel gas in the main chamber of the cylinder.

However, igniting a certain amount of pilot fuel oil increases the amount of unwanted exhaust gases and requires a dedicated fuel oil supply system which further complicates the engine. Furthermore, in the case of a dual fuel engine having both a fuel gas supply system and a fuel oil supply system, the additional reliability of having two fuel systems is partially lost if the engine cannot function without the fuel oil supply system.

Accordingly, there remains a problem in providing an improved two-stroke internal combustion engine.

According to a first aspect, the present invention relates to a uniflow scavenging two-stroke crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system, and a scavenging air system, wherein the cylinder comprises a cylinder a wall, the cylinder cover arranged at the top of the cylinder and having an exhaust valve, the piston being movably arranged in the cylinder between bottom dead center and top dead center along a central axis, and a scavenging air system arranged at the bottom of the cylinder. having an air inlet, wherein the fuel gas supply system is arranged at least partially in the cylinder wall and configured to inject fuel gas into the cylinder during a compression stroke such that the fuel gas is mixed with the scavenge air and prior to ignition the mixture of the scavenge air and the fuel gas and a fuel gas valve allowing the gas to be compressed, wherein the engine further comprises a pre-chamber and a pilot fuel supply system, the pre-chamber opening into the cylinder through the first opening and including an ignition element, the pilot fuel supply The system is configured to inject pilot fuel gas into the pre-chamber during a compression stroke such that the pilot fuel gas is mixed with air and compressed prior to ignition to form a combustible mixture inside the pre-chamber, the ignition element being configured to ignite the pilot fuel gas within the chamber.

Therefore, by using the fuel gas as the pilot fuel, any unwanted exhaust gas resulting from the combustion of the fuel oil can be avoided. Furthermore, the engine can be designed with less fuel supply system, or if the engine is a dual fuel engine, a more reliable engine is provided that can run on fuel gas only.

Preferably the internal combustion engine is a uniflow scavenging, large, low-speed turbocharged, two-stroke crosshead internal combustion engine for propulsion of marine vessels with a power of at least 400 kW per cylinder. An internal combustion engine includes a turbocharger that is driven by exhaust gases generated by the internal combustion engine and is configured to compress scavenging air. The internal combustion engine may be a dual-fuel engine having an auto cycle mode driven by fuel gas and a diesel cycle mode driven by an alternative fuel such as heavy oil or marine diesel oil. Such dual-fuel engines have a dedicated fuel supply system for injecting alternative fuels. During compression, the air from the cylinder or the mixture of air and fuel gas formed in the cylinder will flow into the pre-chamber and mix with the pilot fuel gas.

The ignition element may be a spark plug, corona/plasma igniter, microwave igniter, glow plug, laser igniter, or jet torch.

Preferably the internal combustion engine comprises a plurality of cylinders, for example between 4 and 14. The internal combustion engine further includes a cylinder cover, an exhaust valve, a piston, a fuel gas valve, and a scavenging air inlet for each of the plurality of cylinders.

Preferably, the fuel gas supply system is configured to inject fuel gas via one or more fuel gas valves under sonic conditions, ie a speed equal to the speed of sound, ie a constant velocity. The sonic condition can be achieved when the pressure drop ratio in the nozzle throat (minimum cross-sectional area) is greater than approximately two.

Accordingly, the pilot fuel supply system may be configured to inject pilot fuel gas via the pilot fuel valve into the pre-chamber under sonic conditions.

The one or more fuel gas valves are arranged at least partially in the cylinder wall between top dead center and bottom dead center, preferably at a position above the scavenging air inlet. The one or more fuel gas valves may include a nozzle arranged in the cylinder wall for injecting fuel gas into the cylinder. In some embodiments the ignition element is configured to produce an almost instantaneous maximum energy release upon actuation.

This allows for better control of the ignition timing. Examples of ignition elements capable of producing a near-instantaneous release of energy in operation are spark plugs, corona/plasma igniters, microwave igniters, laser igniters, or jet torches.

In some embodiments, the one or more fuel gas valves direct fuel gas into the cylinder during a compression stroke between 0 degrees and 160 degrees from bottom dead center, or between 0 degrees and 130 degrees from bottom dead center, or between 0 degrees and 90 degrees from bottom dead center. is configured to spray.

Examples of fuel gas include liquefied natural gas (LNG), methane, ethane, and liquefied petroleum gas (LPG).

In some embodiments, the fuel gas supply system and the pilot fuel supply system provide the same fuel gas.

In some embodiments, the engine further comprises a second pre-chamber, the second pre-chamber opening through the second opening into the cylinder and including an ignition element, and wherein the pilot fuel supply system is configured to perform a second pre-chamber during the compression stroke. - configured to inject the pilot fuel gas into the chamber such that the pilot fuel gas can be compressed prior to ignition, and the ignition element is configured to ignite the pilot fuel gas in the pre-chamber.

The two pre-chambers may be identical. The two pre-chambers can be arranged opposite to each other.

The engine may have more pre-chambers, such as at least three or four pre-chambers per cylinder.

In some embodiments, the pilot fuel valve moves pilot fuel into the pre-chamber during the compression stroke at 0 degrees to 160 degrees from bottom dead center, or 0 degrees to 130 degrees from bottom dead center, or 0 degrees to 90 degrees from bottom dead center. configured to inject gas.

In some embodiments, the pilot fuel valve is configured to inject pilot fuel gas during the pilot fuel injection period, wherein the ignition element is configured to ignite the pilot fuel gas in the pre-chamber after the end of the pilot fuel injection period.

Accordingly, proper mixing with the charge air can be achieved by allowing the pilot fuel gas to remain in the pre-chamber prior to ignition. Charge air and fuel gas from the main chamber of the cylinder may enter the pre-chamber before the ignition element is ignited. This makes it possible to reduce the amount of pilot fuel gas to be injected, while still allowing a combustible mixture to be reached.

In some embodiments, the pre-chamber is configured such that the air-fuel equivalence ratio (λ) of the mixture of scavenge air and pilot fuel gas in the pre-chamber upon ignition is λ=1.6, λ=1.5, λ=1.4, or λ=1.3 is below.

This can be done by controlling the amount of pilot fuel gas injected and by designing the shape of the pre-chamber and the first opening so that a desired amount of fuel gas stays in the pre-chamber.

In some embodiments, the ratio between the cross-sectional area of the opening of the pre-chamber into the cylinder measured in m ² and the volume of the pre-chamber measured in m ³ is between 0.5 and 1.2 m ⁻¹ .

Accordingly, it can be ensured that too much pilot fuel gas does not exit the pre-chamber before being ignited.

As an example, if the pre-chamber includes only the first opening and the area of the first opening is 60 mm 2 , and the volume of the pre-chamber is 0.1 liters, the ratio becomes 0.6 m ⁻¹ .

In some embodiments, the engine is configured to ensure that λ of the mixture of scavenge air and fuel gas in the cylinder is λ=2.0 or greater.

In some embodiments, the pre-chamber further comprises a second ignition element.

By providing a pre-chamber with a second ignition element, a more reliable engine is provided as the engine can operate even if one of the ignition elements fails.

In some embodiments, the pre-chamber is arranged at least partially in the cylinder wall and the first opening is formed in the cylinder wall.

In some embodiments, the engine further comprises a pre-chamber cooling system for cooling the pre-chamber, the pre-chamber cooling system comprising a cooling channel proximate the pre-chamber for extracting heat from the pre-chamber and the pre-chamber cooling system is configured to circulate a cooling fluid through the cooling channel.

Arranging the pre-chamber within the cylinder wall provides more space for the pre-chamber cooling system. This makes it possible to more accurately control the temperature of the pre-chamber while being less influenced by other engine parameters such as exhaust valve closing timing, engine speed, engine load, and the like. Precise control of the temperature of the pre-chamber can reduce the risk of misfire, so use pilot fuels that are more difficult to ignite, such as fuel gases such as liquefied natural gas (LNG), methane, ethane and liquefied petroleum gas (LPG). make it more suitable for

In some embodiments, the pre-chamber cooling system further comprises a control unit configured to control the flow of the cooling fluid and/or the inlet temperature of the cooling fluid.

In some embodiments, the control unit is configured to control the flow of the cooling fluid and/or the inlet temperature of the cooling fluid according to the engine load, the engine speed and/or the air-fuel equivalence ratio (λ) of the mixture of scavenged air and fuel gas. is composed

In some embodiments, the cylinder has a base member and a pre-chamber member, wherein the pre-chamber member is arranged on top of the base member and the cylinder cover is arranged on top of the pre-chamber member, wherein the pre-chamber is a pre-chamber member arranged at least partially within a cylinder wall of the chamber member, the pre-chamber opening into the cylinder through an opening formed in the cylinder wall of the pre-chamber member.

This allows the pre-chamber member to be specifically designed to handle the high temperatures and high pressures in the pre-chamber, for example by selecting the appropriate material. This also makes it easier to perform maintenance on the pre-chamber.

The pre-chamber member may be bolted together with the base member of the cylinder. Alternatively, the pre-chamber member may be welded together with the base member of the cylinder.

In some embodiments, the pre-chamber member of the cylinder is made of a different material than the base member of the cylinder.

In some embodiments, the pre-chamber is arranged at least partially in the cylinder cover and the first opening is formed in the cylinder cover.

In some embodiments, the engine is a dual-fuel engine having an auto cycle mode powered by fuel gas and a diesel cycle mode driven by an alternative fuel, the engine further comprising a dedicated alternative fuel supply system for injecting the alternative fuel wherein the alternative fuel supply system comprises one or more fuel injectors arranged on the cylinder cover, wherein the engine, when in diesel cycle mode, injects the alternative fuel at the end of the compression stroke under high pressure using the one or more fuel injectors. and wherein the engine is configured to repeatedly perform a cleaning operation for cleaning the pre-chamber when in a diesel cycle mode.

Thus, the pre-chamber can be protected from combustion by-products resulting from the combustion of the alternative fuel. This allows the engine to reliably switch back to auto cycle mode after a long period of time in diesel cycle mode.

The alternative fuel may be heavy oil or marine diesel oil. The engine may be configured to perform a cleaning operation at each engine cycle. Alternatively, the cleaning operation may be performed at a lower frequency, such as every second engine cycle, every fifth engine cycle, or once daily. The frequency of cleaning operations may be determined based on engine load and/or engine parameter settings such as sensor data recorded by one or more sensors. The cleaning operation may occur at any time during the engine cycle.

In some embodiments, the cleaning operation is configured to remove combustion by-products deposited within the pre-chamber and/or to prevent combustion by-products from depositing within the pre-chamber.

In some embodiments, the cleaning operation includes injecting the first fluid using a pilot fuel valve.

In some embodiments, the first fluid is a fuel gas, atmospheric air, and/or an inert gas.

In some embodiments, the first fluid is atmospheric air or an inert gas wherein the first fluid is used to flush the pre-chamber.

Accordingly, a simple method of cleaning the pre-chamber by flushing the pre-chamber is provided.

Flushing can be performed when the pressure inside the cylinder is low, for example at the beginning of the compression stroke. Injection may occur before the exhaust valve is closed or after the exhaust valve is closed.

In some embodiments, the first fluid is a fuel gas wherein the ignition element is configured to ignite the fuel gas as part of a cleaning operation.

Accordingly, unwanted by-products resulting from the combustion of alternative fuels in the pre-chamber may be incinerated.

In some embodiments, the engine, when in the diesel cycle mode, repeatedly performs a first type of cleaning operation having a first frequency and a second type of cleaning operation having a second frequency to clean the pre-chamber and wherein the second frequency is lower than the first frequency.

In some embodiments, the first type of cleaning action comprises injecting a first fluid using a pilot fuel valve, wherein the first fluid is atmospheric air or an inert gas, wherein the first fluid is configured to flush the pre-chamber. wherein the second type of cleaning operation comprises injecting fuel gas using a pilot fuel valve, wherein the ignition element is configured to ignite the fuel gas as part of the second type of cleaning operation.

Accordingly, the pre-chamber can be effectively kept clean. By only injecting fuel gas as part of a low frequency cleaning operation, the pilot fuel supply system can purge the fuel gas most of the time when the engine is in diesel cycle mode, improving safety. The second frequency may be less than once an hour, once every 6 hours, once every 12 hours, once a day, once every two days, or once a week.

According to a second aspect, the present invention relates to a pre-chamber for use with a uniflow scavenge two-stroke crosshead internal combustion engine as described in relation to the first aspect, wherein the pre-chamber has a first opening wherein the pre-chamber is configured to open into the cylinder through make it possible

Different aspects of the present invention may be implemented in different ways, including a uniflow scavenging two-stroke crosshead internal combustion engine and a pre-chamber as described above and below, each comprising at least one of the aspects described above It yields one or more advantages and advantages described in connection with, each having one or more preferred embodiments corresponding to preferred embodiments described in connection with at least one of the aspects described above and/or disclosed in the dependent claims. Furthermore, it will be understood that an embodiment described in connection with one of the aspects described herein may be equally applicable to another aspect.

According to the present invention, by using fuel gas as pilot fuel, any unwanted exhaust gases resulting from combustion of fuel oil can be avoided. Furthermore, the engine can be designed with less fuel supply system, or if the engine is a dual fuel engine, a more reliable engine is provided that can run on fuel gas only.

According to the present invention, proper mixing with the charge air can be achieved by allowing the pilot fuel gas to remain in the pre-chamber prior to ignition. Charge air and fuel gas from the main chamber of the cylinder may enter the pre-chamber before the ignition element is ignited. This makes it possible to reduce the amount of pilot fuel gas to be injected, while still allowing a combustible mixture to be reached.

According to the present invention, it can be ensured that too much pilot fuel gas does not exit the pre-chamber before being ignited.

According to the present invention, the pre-chamber can be protected from combustion by-products resulting from the combustion of alternative fuels. This allows the engine to reliably switch back to auto cycle mode after a long period of time in diesel cycle mode.

According to the present invention, a simple method for cleaning a pre-chamber by flushing the pre-chamber is provided.

According to the present invention, unwanted by-products resulting from the combustion of alternative fuels in the pre-chamber can be incinerated.

According to the present invention, the pre-chamber can be effectively kept clean. By only injecting fuel gas as part of a low frequency cleaning operation, the pilot fuel supply system can purge the fuel gas most of the time when the engine is in diesel cycle mode, improving safety. The second frequency may be less than once an hour, once every 6 hours, once every 12 hours, once a day, once every two days, or once a week.

The above and/or additional objects, features and advantages of the present invention will be further elucidated by the following illustrative and non-limiting detailed description of embodiments of the present invention, with reference to the accompanying drawings.
1 is a schematic cross-sectional view of a two-stroke internal combustion engine according to an embodiment of the present invention;
2 is a partial schematic cross-sectional view of a uniflow scavenging two-stroke crosshead internal combustion engine according to an embodiment of the present invention.
3 is a partial schematic cross-sectional view of a uniflow scavenging two-stroke crosshead internal combustion engine according to an embodiment of the present invention.
4 is a schematic diagram illustrating a pre-chamber according to an embodiment of the present invention;
5 is a partial schematic cross-sectional view of a uniflow scavenging two-stroke crosshead internal combustion engine according to an embodiment of the present invention.
6 is a schematic diagram illustrating a pre-chamber according to an embodiment of the present invention;

DETAILED DESCRIPTION In the following description, reference is made to the accompanying drawings, which show by way of example how the present invention may be practiced.

1 schematically shows a cross-sectional view of a uniflow scavenging large, low-speed turbocharged two-stroke crosshead internal combustion engine 100 for propulsion of a marine vessel, in accordance with an embodiment of the present invention. The engine 100 includes a scavenging air system 111 , an exhaust gas receiver 108 , a fuel gas supply system, and a turbocharger 109 . The engine has a plurality of cylinders 101 (only a single cylinder is shown in the cross-sectional view). Each cylinder 101 has a cylinder wall 115 and includes a scavenging air inlet 102 arranged at the bottom of the cylinder 101 . The engine further includes a cylinder cover 112 and a piston 103 for each cylinder. A cylinder cover 112 is arranged on top of the cylinder 101 and has an exhaust valve 104 . The piston 103 is arranged movably in the cylinder along a central axis 113 between bottom dead center and top dead center. The fuel gas supply system is configured to inject fuel gas into the cylinder 101 during a compression stroke such that the fuel gas is mixed with the scavenge air and the mixture of the scavenge air and the fuel gas is compressed prior to ignition. a gas valve 105 . The engine further includes a pre-chamber 114 and a pilot fuel supply system, the pre-chamber 114 opening into the cylinder 101 through a first opening and including an ignition element (not shown). The pilot fuel supply system includes a pilot fuel valve (not shown) configured to inject the pilot fuel gas into the pre-chamber during a compression stroke so that the pilot fuel gas can be compressed prior to ignition, and the ignition element injects the pilot fuel gas into the pre-chamber during a compression stroke. configured to ignite within the chamber. However, in this embodiment the pre-chamber 114 is arranged in the cylinder wall 115 , and in another embodiment the pre-chamber 114 may be arranged in the cylinder cover 112 . The scavenging air inlet 102 is fluidly connected to the scavenging air system. The piston 103 is shown in its lowest position (bottom dead center). The piston 103 has a piston rod connected to a crankshaft (not shown). The fuel gas valve 105 is configured to inject fuel gas into the cylinder during the compression stroke, allowing the fuel gas to mix with the scavenge air and allow the mixture of scavenge air and fuel gas to be compressed prior to ignition. The fuel gas valve 105 is arranged at least partially in the cylinder wall between the cylinder cover 112 and the scavenging air inlet 102 , such that for example a fuel gas nozzle of the fuel gas valve 105 can be arranged in the cylinder wall and the fuel The remaining part of the gas valve may be arranged outside the cylinder. The fuel gas valve is configured to inject fuel gas into the cylinder 101 at the beginning of a compression stroke of 0 degrees to 130 degrees from bottom dead center, ie when the crankshaft is rotated 0 degrees to 130 degrees from orientation at bottom dead center. . Preferably, the fuel gas valve 105 is configured such that the crankshaft shaft moves several times from bottom dead center so that the piston moves past the scavenge air inlet 102 to prevent fuel gas from escaping through the scavenge air inlet 102 . It is also configured to start injection of fuel gas after rotation. The scavenge air system 111 includes a scavenge air receiver 110 and an air cooler 106 .

The engine 100 is preferably a dual-fuel engine having an auto cycle mode driven by fuel gas and a diesel cycle mode driven by an alternative fuel such as heavy oil or marine diesel oil. These dual-fuel engines have a dedicated alternative fuel supply system for injecting alternative fuels. Accordingly, optionally the engine 100 further comprises one or more fuel injectors 116 arranged within the cylinder cover 112 forming part of the alternative fuel supply system. When the engine 100 is driven on an alternative fuel, the fuel injector 116 is configured to inject an alternative fuel, eg, heavy oil, at the end of a high-pressure compression stroke.

2 shows a partial schematic cross-sectional view of a uniflow scavenging two-stroke crosshead internal combustion engine according to an embodiment of the present invention. A cylinder 101 , a cylinder cover 112 , a piston 103 , and an exhaust valve 104 are shown. The piston 103 is located at top dead center. The cylinder 101 has a cylinder wall 115 having a first pre-chamber 114 and a second pre-chamber 116 . The first and second pre-chambers 114 and 116 are opened into the cylinder 101 through an opening formed in the cylinder wall 115, and the pre-chambers 114 and 116 are formed of scavenge air and fuel gas in the cylinder. configured to ignite the mixture. The engine further comprises a pilot fuel supply system comprising a first pilot fuel valve arranged in the first pre-chamber 114 and a second pilot fuel valve arranged in the second pre-chamber 116 , the first and The second pilot fuel valve is configured to inject pilot fuel gas into the pre-chamber. The first and second pre-chambers 114 , 116 further include an ignition element configured to ignite the pilot fuel gas.

3 shows a partial schematic cross-sectional view of a uniflow scavenging two-stroke crosshead internal combustion engine according to an embodiment of the present invention. This part corresponds to the part shown in FIG. 2 , but the cylinder 101 has a base member 117 and a pre-chamber member 118 , and the pre-chamber member 118 is disposed on the upper portion of the base member 117 . arranged and the cylinder cover 112 is arranged on top of the pre-chamber member 118 . The first and second pre-chambers 114 , 116 are arranged in the cylinder wall of the pre-chamber member 118 . This allows the pre-chamber member to be specially designed to handle high temperatures and pressures, for example by selecting appropriate materials.

4 shows a schematic diagram of a pre-chamber 114 according to an embodiment of the present invention. The pre-chamber 114 is configured to open into the cylinder through the first opening 123 and the second opening 124 . The pre-chamber includes an ignition element 119 and a pilot fuel valve 120 which injects the pilot fuel gas into the pre-chamber during a compression stroke so that the pilot fuel gas 121 can be compressed before being ignited. is configured to The ignition element 119 is configured to ignite the pilot fuel gas in the pre-chamber to create a flame 122 for igniting the fuel gas in the cylinder.

5 shows a partial schematic cross-sectional view of a uniflow scavenging two-stroke crosshead internal combustion engine according to an embodiment of the present invention. A cylinder 101 , a cylinder cover 112 , and an exhaust valve 104 are shown. The cylinder cover 112 has a first pre-chamber 114 and a second pre-chamber 116 . The first and second pre-chambers 114 and 116 are opened into the cylinder 101 through an opening formed in the cylinder cover 112, and the pre-chambers 114 and 116 are formed of scavenge air and fuel gas in the cylinder. configured to ignite the mixture. The engine further comprises a pilot fuel supply system comprising a first pilot fuel valve arranged in the first pre-chamber 114 and a second pilot fuel valve arranged in the second pre-chamber 116 , the first and The second pilot fuel valve is configured to inject pilot fuel gas into the pre-chamber. The first and second pre-chambers 114 , 116 further include an ignition element configured to ignite the pilot fuel gas.

6 shows a schematic diagram of a pre-chamber 114 according to an embodiment of the present invention. The pre-chamber 114 is configured to open into the cylinder through the first opening 123 and the second opening 124 . The pre-chamber includes an ignition element 119 and a pilot fuel valve 120 which injects the pilot fuel gas into the pre-chamber during a compression stroke so that the pilot fuel gas 121 can be compressed before being ignited. is configured to The ignition element 119 is configured to ignite the pilot fuel gas in the pre-chamber to create a flame 122 for igniting the fuel gas in the cylinder. The engine in the present embodiment is configured to repeatedly perform a cleaning operation for cleaning the pre-chamber 114 when in the diesel cycle mode (thus not using the pre-chamber 114 ). In this embodiment, the pilot fuel valve 120 is fluidly connected to both the gas tank 140 and the N2 tank 130 . The pilot fuel valve 120 is fluidly connected to the gas tank 140 via a compressor 141 configured to compress the gas and a shutoff valve 142 . Correspondingly, the pilot fuel valve 120 is fluidly connected to the N2 tank 130 via a compressor 131 configured to compress the N2 and a shutoff valve 132 . The N2 supply system 130 , 131 , 132 also provides a gas supply system when the gas supply system is not in use, eg using one or more blowout tubes (not shown), eg when the engine is in diesel cycle mode. It may also be used to purge (140, 141, 142). The cleaning operation may be configured to remove combustion by-products deposited within the pre-chamber and/or to prevent combustion by-products from depositing within the pre-chamber. The cleaning operation includes injection of the first fluid using the pilot fuel valve 120 . The first fluid may be N2 supplied from the N2 tank 130 where the first fluid is used to flush the pre-chamber 114 . Alternatively/additionally, the first fluid may be fuel gas supplied from the gas tank 140 wherein the ignition element 119 is configured to ignite the fuel gas as part of a cleaning operation, and thus undesired Combustion by-products may be combusted.

While some embodiments have been described and shown in detail, the invention is not limited thereto, but may be embodied in other ways within the scope of the subject matter defined in the claims that follow. In particular, it is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention.

In the device claim enumerating several means, some of these means may be embodied by one and the same item of hardware. The fact that certain measures are recited in different dependent claims or are described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

As used herein, the term "comprises/comprising" is used to specify the presence of a recited feature, integer, step or element, but one or more other features, integers, steps, configurations. It should be emphasized that this does not exclude the presence or addition of elements or groups thereof.

100: (2-stroke uniflow scavenge crosshead internal combustion) engine, 101 cylinder, 102 scavenging air inlet, 103 piston, 104 exhaust valve, 105 fuel gas valve, 111 scavenging air system, 112 cylinder Cover, 113: central axis, 114: pre-chamber, 115: cylinder wall, 119: ignition element, 120: pilot fuel valve, 121: pilot fuel gas, 123: first opening.

Claims (19)

A uniflow scavenging two-stroke crosshead internal combustion engine (100) comprising at least one cylinder (101), a cylinder cover (112), a piston (103), a fuel gas supply system, and a scavenging air system (111);
The cylinder has a cylinder wall (115),
the cylinder cover is arranged on top of the cylinder and has an exhaust valve (104);
the piston is arranged movably within the cylinder along a central axis 113 between bottom dead center and top dead center;
The scavenging air system 111 has a scavenging air inlet 102 arranged at the bottom of the cylinder,
The fuel gas supply system is arranged at least partially on the cylinder wall and configured to inject fuel gas into the cylinder during a compression stroke such that the fuel gas is mixed with the scavenge air and the mixture of scavenge air and fuel gas is compressed prior to ignition. and a fuel gas valve (105) allowing it to be
The engine further comprises a pre-chamber (114) and a pilot fuel supply system,
the pre-chamber (114) opens into the cylinder through an opening (123) and includes an ignition element (119);
the pilot fuel supply system is configured to inject pilot fuel gas (121) into the pre-chamber during a compression stroke so that the pilot fuel gas can be compressed prior to ignition;
A two-stroke crosshead internal combustion engine, characterized in that the ignition element (119) is configured to ignite the pilot fuel gas (121) in the pre-chamber (114). The method according to claim 1,
wherein the fuel gas supply system and the pilot fuel supply system provide the same fuel gas. The method according to claim 1 or 2,
The pilot fuel valve 120 enters the pre-chamber 114 during a compression stroke at 0 degrees to 160 degrees from bottom dead center, or 0 degrees to 130 degrees from bottom dead center, or 0 degrees to 90 degrees from bottom dead center. A two-stroke crosshead internal combustion engine configured to inject pilot fuel gas (121). 4. The method according to claim 3,
The pilot fuel valve 120 is configured to inject pilot fuel gas 121 during a pilot fuel injection period, and the ignition element 119 is configured to inject pilot fuel gas 121 into the pre-chamber 114 after the end of the pilot fuel injection period. A two-stroke crosshead internal combustion engine configured to ignite fuel gas (121). 5. The method according to claim 4,
the pre-chamber 114 is configured to ensure that the air-fuel equivalence ratio λ of the mixture of scavenge air and pilot fuel gas 121 in the pre-chamber 114 is λ=1.6 or less upon ignition -Stroke crosshead internal combustion engine. 6. The method of claim 5,
The ratio between the cross-sectional area of the openings 123 , 124 of the pre-chamber 114 into the cylinder 101 measured in m ² and the volume of the pre-chamber measured in m ³ is 0.5 to 1.2 m ^- Between ¹ , 2-stroke crosshead internal combustion engines. 7. The method of claim 6,
wherein the engine is configured to ensure that λ of the mixture of scavenge air and fuel gas in the cylinder is λ=2.0 or greater. 8. The method according to any one of claims 1 to 7,
wherein the pre-chamber (114) is arranged at least partially in the cylinder wall (115) and the opening (123) is formed in the cylinder wall. 9. The method of any one of claims 1 to 8,
wherein the pre-chamber (114) is arranged at least partially in the cylinder cover (112) and the opening (123) is formed in the cylinder cover (112). 10. The method according to any one of claims 1 to 9,
wherein the ignition element (119) is configured to produce an instantaneous maximum energy release in operation. 10. The method according to any one of claims 1 to 9,
The engine is a dual-fuel engine having an auto cycle mode driven by fuel gas and a diesel cycle mode driven by an alternative fuel, the engine further comprising an alternative fuel supply system dedicated to injecting the alternative fuel, the replacement fuel The fuel supply system comprises one or more fuel injectors arranged in the cylinder cover,
the engine is configured to inject an alternative fuel at the end of a compression stroke under high pressure using one or more fuel injectors when in a diesel cycle mode;
and the engine is configured to repeatedly perform a cleaning operation to clean the pre-chamber when in a diesel cycle mode. 12. The method of claim 11,
wherein the cleaning operation is configured to remove combustion by-products deposited in the pre-chamber and/or to prevent combustion by-products from depositing in the pre-chamber. 13. The method of claim 11 or 12,
and wherein the cleaning operation comprises injecting a first fluid using the pilot fuel valve. 13. The method of claim 12,
wherein the first fluid is fuel gas, atmospheric air and/or an inert gas. 15. The method of claim 14,
wherein the first fluid is atmospheric air or an inert gas and the first fluid is used to flush the pre-chamber. 14. The method of claim 13,
wherein the first fluid is fuel gas and the ignition element is configured to ignite the fuel gas as part of a cleaning operation. 17. The method according to any one of claims 11 to 16,
the engine, when in a diesel cycle mode, repeatedly performs a first type of cleaning operation having a first frequency and a second type of cleaning operation having a second frequency to clean the pre-chamber; and wherein the second frequency is lower than the first frequency. 18. The method of claim 17,
The first type of cleaning operation includes injecting a first fluid using the pilot fuel valve, wherein the first fluid is atmospheric air or an inert gas and the first fluid is used to flush the pre-chamber wherein the second type of cleaning operation comprises injecting fuel gas using the pilot fuel valve and the ignition element is configured to ignite the fuel gas as part of the second type of cleaning operation; Stroke crosshead internal combustion engine. 11. A pre-chamber for use with a two-stroke crosshead internal combustion engine according to any one of the preceding claims, comprising:
the pre-chamber (114) is configured to open into the cylinder (101) through an opening (123) and comprises an ignition element (119);
The pre-chamber further comprises a pilot fuel valve (120) configured to inject pilot fuel gas (121) into the pre-chamber (114) during a compression stroke so that the pilot fuel gas (121) can be compressed prior to ignition. and
and the ignition element (119) is configured to ignite pilot fuel gas (121) in the pre-chamber (114).

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