Internal combustion engine

Abstract

A two-stroke uniflow scavenging crosshead type internal combustion engine including at least one cylinder is disclosed. The engine includes a main fuel supply system configured to provide an ammonia-based fuel into the main combustion chamber, where the engine further includes a pilot fuel system including at least one pilot fuel injector configured to inject a pilot fuel to ignite the ammonia-based fuel, wherein the pilot fuel comprises a compound that is ammonia or is derivable from ammonia. The engine also includes a standby fuel supply system including at least one standby fuel injector configured to inject a self-ignitable fuel, where the engine is configured to be operable in a first mode in which the engine is configured to be operated in a second mode in which the engine is configured to be operated in a second mode in which the engine is configured to be operated in a second mode. The main fuel supply system and the pilot fuel supply system are enabled and the standby fuel supply system is disabled, and a second mode in which the standby fuel supply system is enabled.

Description

Technical Field

[0001] The present invention relates to a two-stroke single-flow scavenging crosshead type internal combustion engine. Background Art

[0002] Two-stroke internal combustion engines are used as propulsion engines in ships such as container ships, bulk carriers, and tankers. Reducing carbon emissions from internal combustion engines has become increasingly important.

[0003] An effective way to reduce carbon emissions is to switch from fuels such as heavy fuel oil (HFO) to non-carbon-based fuels. Ammonia has shown great potential as a non-carbon-based fuel. However, ammonia has poor auto-ignition properties, so a certain amount of diesel fuel is often used as a pilot fuel to ignite the ammonia.

[0004] However, the combustion of diesel pilot fuel produces carbon emissions.

[0005] When internal combustion engines are used as propulsion engines in ships, engine reliability becomes critical, as loss of engine power can lead to catastrophic events.

[0006] Keeping such propulsion engines low-cost is another key priority in enabling a rapid transition from carbon-based to non-carbon-based fuels.

[0007] Therefore, providing an improved internal combustion engine capable of combusting ammonia remains a challenge. Summary of the Invention

[0008] According to a first aspect, the present invention relates to a two-stroke single-flow scavenged crosshead type internal combustion engine, the two-stroke single-flow scavenged crosshead type internal combustion engine comprising at least one cylinder, a cylinder head, a piston, a main fuel supply system, and a scavenging system, the cylinder having a cylinder wall, the cylinder head being arranged at the top of the cylinder and having an exhaust valve, the piston being movably arranged in the cylinder between a bottom dead center and a top dead center along a central axis, the scavenging system having a scavenging inlet arranged at the bottom of the cylinder, the main fuel supply system being configured to provide an ammonia-based fuel into a main combustion chamber defined between the piston and the cylinder head, wherein the engine further comprises a pilot fuel supply system, the pilot fuel supply system The system includes at least one pilot fuel injector, which is configured to inject a pilot fuel to ignite an ammonia-based fuel, wherein the pilot fuel contains ammonia or a compound derivable from ammonia, wherein the engine further includes a backup fuel supply system, which includes at least one backup fuel injector, which is configured to inject a self-igniting fuel, wherein the engine is configured to operate in a first mode and a second mode, in which the main fuel supply system and the pilot fuel supply system are enabled and the backup fuel supply system is disabled, and in the second mode, the backup fuel supply system is enabled.

[0009] Thus, by providing the engine with a third fuel supply system, the engine may remain operable even when one of the other two fuel supply systems becomes inoperable, for example due to a failure or maintenance.

[0010] The internal combustion engine is preferably a large, low-speed, turbocharged, two-stroke, uniflow, scavenged, crosshead-type internal combustion engine for propulsion of ships or stationary power plants, with a power output of at least 400 kW per cylinder. The internal combustion engine may include a turbocharger driven by exhaust gases generated by the internal combustion engine and configured to compress the scavenged gases.

[0011] The internal combustion engine preferably comprises a plurality of cylinders, for example 4 to 14 cylinders.

[0012] The main fuel supply system may comprise one or more fuel injectors arranged in the cylinder head, the one or more fuel injectors being configured to inject the ammonia based fuel at a high pressure, for example between 250 and 800 bar, at the end of the compression stroke.

[0013] Alternatively, the primary fuel supply system may include a fuel admission valve configured to admit ammonia-based fuel to the cylinder during the compression stroke, for example, within 0 to 160 degrees from bottom dead center, within 0 to 130 degrees from bottom dead center, or within 0 to 90 degrees from bottom dead center. This allows the ammonia-based fuel to mix with the scavenging gas and compress the scavenging gas-fuel mixture prior to ignition. The fuel admission valve may be configured to admit the ammonia-based fuel at a low pressure, for example, between 5 and 50 bar.

[0014] An ammonia-based fuel may contain ammonia mixed with one or more elements. As an example, an ammonia-based fuel may contain ammonia and one or more of the following elements: a carbon-based fuel, hydrogen, and water.

[0015] The carbon-based fuel may include one or more of the following carbon-based fuels: liquefied natural gas (LNG), methane, ethane, and liquefied petroleum gas (LPG), marine gas oil (MGO), marine diesel (MDO), intermediate fuel oil (IFO), marine fuel oil (MFO), heavy fuel oil (HFO), and marine diesel.

[0016] In some embodiments, the mass percentage of ammonia in the ammonia-based fuel is at least 50%, at least 80%, at least 90%, or at least 95%.

[0017] The mass percentage of ammonia in an ammonia-based fuel is given by the following equation:

[0018]

[0019] Among them, m% a_abf is the mass percentage of ammonia in the ammonia-based fuel, m a_abf is the mass of ammonia in the ammonia-based fuel, m t_abf is the total mass of the ammonia-based fuel.

[0020] The pilot fuel may be generated on board the vessel from ammonia for the ammonia-based fuel by using a pilot fuel comprising a compound that is ammonia or derivable from ammonia. Hydrogen (H2) is an example of a compound derivable from ammonia.

[0021] The pilot fuel may comprise one or more compounds that are ammonia or derivable from ammonia, wherein the mass percentage of the one or more compounds that are ammonia or derivable from ammonia in the pilot fuel is at least 50%, at least 80%, at least 90%, or at least 95%.

[0022] The mass percentage of one or more compounds that are ammonia or are derivable from ammonia is given by the following equation:

[0023]

[0024] Among them, m% ad_pf is the mass percentage of one or more compounds that are ammonia or can be derived from ammonia in the pilot fuel, m ad_pf is the mass of one or more compounds that are ammonia or can be derived from ammonia in the pilot fuel, m t_pf is the total mass of the pilot fuel.

[0025] The pilot fuel may self-ignite at the temperature and pressure at the end of the compression stroke. Alternatively, the pilot fuel may be ignited by an ignition element.

[0026] The autoignitable fuel injected by the backup fuel injector may be a carbon-based fuel. The carbon-based fuel may include one or more of the following carbon-based fuels: liquefied natural gas (LNG), methane, ethane, and liquefied petroleum gas (LPG), marine gas oil (MGO), marine diesel (MDO), intermediate fuel oil (IFO), marine fuel oil (MFO), and heavy fuel oil (HFO).

[0027] In some embodiments, the pilot fuel comprises a compound derivable from ammonia that is hydrogen, and wherein the pilot fuel supply system is connectable to a hydrogen production unit configured to produce hydrogen from ammonia.

[0028] The hydrogen production unit can be configured to catalytically decompose ammonia into hydrogen and nitrogen at high temperature. The catalyst can be a ruthenium-based catalyst or a nickel-based catalyst. The hydrogen production unit can be configured to catalytically decompose ammonia into hydrogen using a photocatalytically driven reformer.

[0029] In some embodiments, the engine is configured such that in the second mode, the main fuel supply system is enabled and the pilot fuel supply system is disabled, and wherein the engine is configured to ignite the ammonia-based fuel using autoignitable fuel injected by a fuel injector of the backup fuel supply system.

[0030] Thus, when the hydrogen production unit is unavailable to produce hydrogen for the pilot fuel supply system, the backup fuel supply system may serve as a backup pilot fuel supply system.

[0031] This may allow the hydrogen production unit to rely on excess heat from the engine to reach the temperature required to effectively catalytically decompose ammonia into hydrogen because the backup fuel supply system may be used as a backup pilot fuel supply system during engine startup until the engine has reached the temperature necessary to enable the hydrogen production unit to function.

[0032] This may further allow the engine to be designed without a redundant hydrogen production unit, since the backup fuel supply system may ensure the functionality of the engine even when the hydrogen production unit is unavailable, for example due to routine maintenance or a malfunction.

[0033] The backup fuel injector may be configured to inject the autoignitable fuel at the end of the compression stroke, whereby the autoignitable fuel ignites immediately after being injected.

[0034] In some embodiments, the engine is configured to operate in a third mode in which both the main fuel supply system and the pilot fuel supply system are disabled and the backup fuel supply system is enabled, and wherein the backup fuel supply system is configured to provide all fuel required to maintain operation of the engine.

[0035] The backup fuel supply system may be sized to operate the engine at at least 60%, 80%, 90% or 100% of the rated power of the engine in the third mode.

[0036] In some embodiments, the hydrogen production unit relies on excess heat from the engine to reach the temperature required to effectively catalytically decompose ammonia into hydrogen.

[0037] As an example, the hydrogen production unit may be configured to extract heat from the exhaust gas, with the exhaust gas from which the heat is extracted optionally forming part of an exhaust gas recirculation (EGR) system and configured to reduce the temperature of the exhaust gas before it is delivered back to the cylinders.

[0038] In some embodiments, the engine further comprises a compression ignition pre-chamber unit in which a pilot fuel valve is arranged, and wherein the pilot fuel is an autoignitable pilot fuel.

[0039] The engine can thus safely ignite the ammonia-based main fuel in a simple and reliable manner.

[0040] The compression ignition pre-chamber unit can be designed to provide the temperature and pressure required to autoignite the pilot fuel. The compression ignition pre-chamber unit can be a traditional single-chamber pre-chamber or a multi-chamber pre-chamber including two or more chambers. The compression ignition pre-chamber unit can be arranged in the cylinder head.

[0041] The pilot fuel may comprise a mixture of one or more compounds that are ammonia or derivable from ammonia and one or more carbon-based fuels such as liquefied natural gas (LNG), methane, ethane, and liquefied petroleum gas (LPG), marine gas oil (MGO), marine diesel (MDO), intermediate fuel oil (IFO), marine fuel oil (MFO), heavy fuel oil (HFO), and seal oil.

[0042] In some embodiments, the engine further includes a sealing oil system configured to provide autoignitable sealing oil to the pilot fuel system at a pressure that ensures a certain amount of sealing oil leaks into the pilot fuel, wherein the certain amount of sealing oil leaked into the pilot fuel makes the pilot fuel autoignitable.

[0043] Thus, a simple way of making the pilot fuel self-ignitable is provided.

[0044] In some embodiments, the main fuel system includes at least one main fuel injector arranged in the cylinder head, the main fuel injector being configured to inject an ammonia-based fuel into the combustion chamber at the end of the compression stroke, and wherein the engine further includes a jet pre-combustion chamber unit, in which a pilot fuel injector is arranged, the pilot fuel injector being configured to inject a pilot fuel into the pre-combustion chamber unit, wherein the jet pre-combustion chamber unit further includes an ignition element configured to ignite the pilot fuel.

[0045] Therefore, a high-pressure ammonia engine can be ignited without a large amount of carbon-based fuel used as a pilot fuel.

[0046] The use of a jet pre-chamber allows the ignition energy from the pilot fuel to be directed to the area of ​​the combustion chamber where the ammonia-based fuel is to be injected, thereby producing a more efficient and stable ignition.

[0047] The ignition element can be a spark plug, corona / plasma igniter, microwave ignition system, glow plug, laser igniter or ion system.

[0048] In some embodiments, the jet pre-combustion chamber unit is provided with an opening to the main combustion chamber to guide the jet flame of the burning pilot fuel into the main combustion chamber along a first central axis, and at least one main fuel injector is configured to inject the ammonia-based fuel in the form of a jet along a second central axis, wherein the first central axis and the second central axis are arranged so that the jet flame of the burning pilot fuel contacts the jet of the ammonia-based fuel.

[0049] In some embodiments, the first central axis and the second central axis intersect.

[0050] In some embodiments, the angle between the first central axis and the second central axis is less than 25 degrees, 18 degrees, or 10 degrees.

[0051] In some embodiments, the jet pre-burner unit is provided with a single opening to the main combustion chamber to direct a single jet flame of burning pilot fuel into the main combustion chamber.

[0052] Thus, all the energy from the jet preburner unit can be directed to the injected ammonia based main fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and / or additional objects, features and advantages of the present invention will be further described by the following illustrative and non-limiting detailed description of embodiments of the present invention with reference to the accompanying drawings, in which:

[0054] Figure 1 A cross section of a two-stroke internal combustion engine according to an embodiment of the present disclosure is schematically shown.

[0055] Figure 2a A compression ignition pre-chamber unit 200 is schematically shown according to an embodiment of the present disclosure.

[0056] Figure 2b A jet pre-combustor unit 200 according to an embodiment of the present disclosure is schematically shown.

[0057] Figure 3 A portion of an engine 200 is schematically shown according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0058] In the following description, reference is made to the accompanying drawings that show, by way of illustration, how the invention may be practiced.

[0059] Figure 1 A cross-section of a large, low-speed, turbocharged, two-stroke, single-flow, scavenged, crosshead-type internal combustion engine 100 for propulsion of a ship according to an embodiment of the present invention is schematically shown. The engine 100 includes a scavenging system 111, an exhaust gas receiver 108, a main fuel supply system, a pilot fuel supply system, a backup fuel supply system, and a turbocharger 109. The engine has a plurality of cylinders 101 (only a single cylinder is shown in the cross-section). 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 head 112 and a piston 103 for each cylinder. The cylinder head 112 is arranged on top of the cylinder 101 and has an exhaust valve 104. The piston 103 is movably arranged within the cylinder along a central axis 113 between bottom dead center and top dead center. The main fuel supply system is configured to provide an ammonia-based fuel to a main combustion chamber defined between the piston 103 and the cylinder head 112. The main fuel supply system may include one or more fuel injectors 116 arranged in the cylinder head, which are configured to inject the ammonia based fuel at a high pressure, for example between 250 bar and 800 bar, at the end of the compression stroke.

[0060] Alternatively, the main fuel supply system can be a fuel supply system that includes one or more fuel admission valves 105 configured to admit ammonia-based fuel to the cylinder during the compression stroke, for example, within 0 to 160 degrees from bottom dead center, within 0 to 130 degrees from bottom dead center, or within 0 to 90 degrees from bottom dead center. This allows the ammonia-based fuel to mix with the scavenging gas and allows the scavenging gas-fuel mixture to be compressed before ignition. The fuel admission valves 105 can be configured to admit the ammonia-based fuel at a low pressure, for example, between 5 and 50 bar. The one or more fuel admission valves 105 can be at least partially disposed in the cylinder liner wall. The ammonia can be received from an ammonia storage tank 190.

[0061] The pilot fuel supply system includes at least one pilot fuel injector 114 configured to inject a pilot fuel to ignite an ammonia-based fuel, wherein the pilot fuel comprises ammonia or a compound derivable from ammonia. The compound may be hydrogen. The pilot fuel supply system may be connectable to a hydrogen production unit 191 configured to produce hydrogen from ammonia in the vessel. The hydrogen production unit 191 may be operatively connected to an ammonia tank 190 and configured to receive ammonia from the ammonia tank 190.

[0062] The backup fuel supply system includes at least one backup fuel injector 180 configured to inject autoignitable fuel. The backup fuel injector 180 may be disposed in the cylinder head 112. The autoignitable fuel injected by the backup fuel injector 180 may be a carbon-based fuel stored in a fuel tank 181.

[0063] The engine may be configured to operate in a first mode in which the main and pilot fuel supply systems are enabled and the backup fuel supply system is disabled, and a second mode in which the backup fuel supply system is enabled.

[0064] The engine may be configured such that in a second mode, the main fuel supply system is enabled and the pilot fuel supply system is disabled, and wherein the engine is configured to ignite the ammonia-based fuel using autoignitable fuel injected by a fuel injector of the backup fuel supply system.

[0065] Thus, when the hydrogen production unit is unavailable to produce hydrogen for the pilot fuel supply system, the backup fuel supply system may serve as a backup pilot fuel supply system.

[0066] Figure 2aA compression-ignition pre-chamber unit 200 is shown, according to an embodiment of the present disclosure. Compression-ignition pre-chamber unit 200 is a conventional single-chamber pre-chamber. A pilot fuel valve 203 is disposed within compression-ignition pre-chamber unit 200 and is configured to inject an autoignitable pilot fuel comprising ammonia or a compound derivable from ammonia. For example, the compound may be hydrogen.

[0067] Thus, ammonia can be used as the main component of both the main fuel and the main component for preparing the pilot fuel. This can allow the design of a simple propulsion system, the operation of which can produce no or very low carbon emissions.

[0068] Figure 2b A jet precombustor unit 200 according to an embodiment of the present disclosure is shown. The jet precombustor unit 200 is a conventional single-chamber precombustor. The jet precombustor unit 200 includes a pilot fuel injector 213 configured to inject a pilot fuel comprising ammonia or a compound derivable from ammonia. For example, the compound may be hydrogen. The precombustor unit further includes an ignition element 214 configured to ignite the pilot fuel. The ignition element 214 is preferably a spark plug.

[0069] The compression ignition pre-chamber and / or the jet ignition pre-chamber can be used with a high-pressure main fuel supply system including one or more fuel injectors 116 arranged in the cylinder head, the one or more fuel injectors being configured to inject the ammonia-based fuel at the end of the compression stroke. Alternatively, the compression ignition pre-chamber unit and / or the jet ignition pre-chamber unit can be used with a low-pressure main fuel supply system including one or more fuel admission valves 105 configured to admit the ammonia-based fuel to the cylinder during the compression stroke.

[0070] Figure 3 1 shows a portion of an engine 200 according to an embodiment of the present disclosure. The engine 200 may be substantially similar to the engine 200 of FIG. Figure 1 The disclosed engine corresponds, however, only the upper left corner of the cylinder is shown. The engine comprises a cylinder having a cylinder wall 215, a cylinder head 212, a main fuel injector 216 arranged in the cylinder head 212, and a pre-combustion chamber unit 214. The pre-combustion chamber unit 214 may be as described with respect to Figure 2a The disclosed compression ignition pre-chamber unit or as described in relation to Figure 2bA jet-ignited pre-combustion chamber unit is disclosed. A main fuel injector 216 is configured to inject an ammonia-based fuel under high pressure into the combustion chamber at the end of the compression stroke. The pre-combustion chamber unit 214 is provided with an opening to the main combustion chamber to direct the flame of the burning pilot fuel into the main combustion chamber along a first central axis 251. The main fuel injector 216 is configured to inject the ammonia-based fuel in the form of a jet along a second central axis 250, wherein the first and second central axes are arranged such that the jet flame of the burning pilot fuel contacts the jet of ammonia-based fuel. Preferably, the pre-combustion chamber unit has a single opening to concentrate the ignition energy from the pilot fuel along the first central axis 251.

[0071] In this embodiment, the first central axis 251 and the second central axis intersect, and an angle 252 is provided between the first central axis 251 and the second central axis 250. Preferably, the angle 252 should be kept relatively narrow to ensure that the energy provided by the jet from the pre-combustion chamber unit 214 is concentrated on the main fuel jet. As an example, the angle 252 can be less than 25 degrees, 18 degrees, or 10 degrees.

[0072] Thus, by using a pre-chamber having a specific alignment relative to the main fuel injector, a large bore engine provided with a high pressure fuel supply system can be operated with no or very little carbon based pilot fuel, thereby allowing the operation of the engine without producing any substantial carbon emissions.

[0073] Although some embodiments have been described and shown in detail, the present invention is not limited thereto, but may also be implemented in other ways within the scope of the subject matter defined in the appended claims. In particular, it should be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the scope of the present invention.

[0074] In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

[0075] It should be emphasized that when used in this specification, the term "comprises / comprising" is used to indicate the presence of stated features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Claims

1. A two-stroke, single-flow, scavenged crosshead internal combustion engine, comprising at least one cylinder, a cylinder head, a piston, a main fuel supply system, and a scavenging system, wherein the cylinder has a cylinder wall, the cylinder head is arranged at the top of the cylinder and has an exhaust valve, the piston is movably arranged in the cylinder along a central axis between a bottom dead center and a top dead center, the scavenging system has a scavenging inlet arranged at the bottom of the cylinder, the main fuel supply system is configured to provide an ammonia-based fuel into a main combustion chamber defined between the piston and the cylinder head, wherein: The engine further includes a pilot fuel system comprising at least one pilot fuel injector configured to inject a pilot fuel to ignite the ammonia-based fuel, wherein the pilot fuel comprises ammonia or a compound capable of being derived from ammonia, characterized in that the engine further includes a backup fuel supply system comprising at least one backup fuel injector configured to inject a self-igniting fuel, wherein the engine is configured to be capable of operating in a first mode and a second mode, wherein in the first mode the main fuel supply system and the pilot fuel supply system are enabled and the backup fuel supply system is disabled, and in the second mode the backup fuel supply system is enabled.

2. The two-stroke single-flow scavenging crosshead internal combustion engine according to claim 1, wherein: The pilot fuel comprises a compound derivable from ammonia, the compound being hydrogen, and wherein the pilot fuel supply system is connectable to a hydrogen production unit configured to produce hydrogen from ammonia.

3. The two-stroke single-flow scavenging crosshead internal combustion engine according to claim 2, wherein: In the second mode, the main fuel supply system is enabled and the pilot fuel supply system is disabled, and wherein the engine is configured to ignite the ammonia-based fuel using the autoignitable fuel injected by the fuel injector of the backup fuel supply system.

4. The two-stroke single-flow scavenging crosshead internal combustion engine according to any one of claims 1 to 3, wherein: The engine further comprises a compression-ignition pre-chamber unit in which a pilot fuel valve is arranged, and wherein the pilot fuel is an autoignitable pilot fuel.

5. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 4, wherein: The engine further includes a sealing oil system configured to provide autoignitable sealing oil to the pilot fuel system at a pressure that ensures a certain amount of sealing oil leaks into the pilot fuel, wherein the certain amount of sealing oil leaking into the pilot fuel enables the pilot fuel to autoignite.

6. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 3, wherein: The main fuel system includes at least one main fuel injector arranged in the cylinder head, the main fuel injector being configured to inject the ammonia-based fuel into the combustion chamber at the end of the compression stroke, and wherein the engine further includes a jet pre-combustion chamber unit, in which a pilot fuel injector is arranged, the pilot fuel injector being configured to inject the pilot fuel into the pre-combustion chamber, wherein the jet pre-combustion chamber unit further includes an ignition element configured to ignite the pilot fuel.

7. The two-stroke single-flow scavenging crosshead internal combustion engine according to claim 6, wherein: The jet pre-combustion chamber unit is provided with an opening to the main combustion chamber to guide the jet flame of the burning pilot fuel into the main combustion chamber along a first central axis, and the at least one main fuel injector is configured to inject the ammonia-based fuel in the form of a jet along a second central axis, wherein the first central axis and the second central axis are arranged so that the jet flame of the burning pilot fuel contacts the jet of the ammonia-based fuel.

8. The two-stroke single-flow scavenging crosshead internal combustion engine according to claim 7, wherein: The first central axis and the second central axis intersect.

9. The two-stroke single-flow scavenging crosshead internal combustion engine according to claim 8, wherein: The angle between the first central axis and the second central axis is less than 25 degrees, 18 degrees or 10 degrees.

10. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 6 to 9, wherein: The jet pre-combustor unit is provided with a single opening to the main combustion chamber for directing a single jet flame of burning pilot fuel into the main combustion chamber.

Images