Internal combustion engine

Abstract

A method for allowing fuel gas to enter a two-stroke, single-flow, scavenging crosshead internal combustion engine is disclosed. Compared to the distribution of fuel gas in the cylinder when the axis of the first nozzle is at an angle A along the scavenging vortex direction, the distribution of fuel gas in the cylinder at the end of the compression stroke is less uniform when fuel gas is allowed to enter the cylinder via a first fuel gas valve along the axis of the first nozzle, which is at an angle A relative to the radial direction in the direction opposite to the scavenging vortex direction. This increases the risk of premature ignition. In this method, an exhaust gas recirculation (EGR) system is used to supply a certain amount of exhaust gas to the cylinder to address the increased risk of premature ignition.

Description

Technical Field

[0001] This invention relates to a method for allowing fuel gas to enter a two-stroke single-flow scavenging crosshead internal combustion engine, and to a two-stroke single-flow scavenging crosshead internal combustion engine. Background Technology

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

[0003] An effective way to reduce unwanted exhaust emissions is to replace fuels such as heavy fuel oil (HFO) with fuel gas. Fuel gas can be injected into the cylinder at the end of the compression stroke, where it can be immediately ignited by the high temperatures reached during compression or by igniting the ignition source. 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 before injection to overcome the higher pressure in the cylinder.

[0004] However, the manufacture and maintenance of high-pressure gas compressors are expensive and complex. One way to avoid the need for a high-pressure compressor is to have a fuel gas valve configured to inject fuel gas during the compression stroke when the pressure in the cylinder is significantly lower.

[0005] However, the presence of fuel gas in the cylinder during the compression stroke can lead to the risk of pre-ignition. This is problematic because pre-ignition causes increased wear on engine parts, while measures to avoid pre-ignition result in reduced efficiency.

[0006] As is well known, the uniformity of fuel gas distribution in the cylinder is a key parameter to avoid premature ignition.

[0007] Therefore, much attention in this technical field has been devoted to designing fuel gas supply systems that allow fuel gas to enter the cylinder in a manner that improves the uniformity of fuel gas distribution.

[0008] US201501675538 discloses a system in which fuel gas is injected along the direction of a scavenging vortex, thereby achieving high uniformity.

[0009] Another example is disclosed in WO 2021110229, in which fuel gas is injected in a pulsed manner to improve uniformity.

[0010] Another example is disclosed in JP 2020016171, in which the fuel injection device includes a plurality of fuel injection nozzles for injecting fuel toward the combustion chamber of a two-stroke engine.

[0011] Although modern fuel gas supply systems have reached a point where they can effectively handle pre-ignition, further improvements in fuel consumption and reductions in unwanted emissions remain challenges. Summary of the Invention

[0012] According to a first aspect, the present invention relates to a method for allowing fuel gas to enter a two-stroke single-flow scavenging crosshead internal combustion engine, the two-stroke single-flow scavenging crosshead internal combustion engine including at least one cylinder, a cylinder head, a piston, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system. The cylinder has cylinder walls, the cylinder head is disposed on the top of the cylinder and has an exhaust valve, the piston is movably disposed within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system has a scavenging inlet disposed at the bottom of the cylinder, the scavenging inlet being configured to allow scavenging gas to enter the cylinder, thereby forming a scavenging vortex rotating about the central axis, and the fuel gas supply system including a first fuel gas valve for the cylinder, the first fuel gas valve being configured to allow fuel gas to enter the cylinder. During the compression stroke, fuel gas enters the cylinder via a first fuel gas nozzle at least partially disposed in the cylinder wall, allowing the fuel gas to mix with scavenging gas from the scavenging inlet and permitting the mixture of scavenging gas and fuel gas to be compressed before ignition. However, compared to the distribution of fuel gas within the cylinder when the axis of the first nozzle is at an angle A relative to the radial direction, the distribution of fuel gas within the cylinder at the end of the compression stroke is less uniform due to the fuel gas being permitted to enter the cylinder via a first fuel gas valve along the axis of the first nozzle, which is at an angle A relative to the radial direction in the direction opposite to the scavenging vortex. This results in an increased risk of premature ignition. Furthermore, an exhaust gas recirculation (EGR) system is used to supply a certain amount of exhaust gas to the cylinder to address the increased risk of premature ignition.

[0013] Surprisingly, it was found that by injecting fuel gas in a manner that resulted in a less uniform distribution of fuel gas and simultaneously using an EGR system to address the increased risk of premature ignition, fuel consumption was improved, heat load on components was reduced, and emissions were lowered.

[0014] The normal injection of fuel gas along the vortex direction causes the fuel jet to impact the opposing liner, thereby facilitating rapid vertical diffusion of the gas within the cylinder. This results in a very uniform distribution of fuel gas, especially for fuel gas supply systems with few fuel gas valves (e.g., no more than two), particularly when the fuel gas valves are arranged at substantially the same height within the cylinder.

[0015] Injecting fuel gas in the opposite direction to the vortex also causes the fuel jet to impact the opposing liner wall, but with less aggression, thus weakening vertical diffusion. This results in a less uniform distribution of fuel gas, particularly for fuel gas supply systems with few fuel gas valves (e.g., no more than two), especially when the fuel gas valves are arranged at substantially the same height within the cylinder. It has been found that, since the gas appears to burn further away from the wall, reverse vortex gas injection can be used to reduce higher wall temperatures, thereby improving fuel efficiency.

[0016] The axis of the first nozzle extends along a first direction vector. The first direction vector includes radial and tangential components arranged in a plane perpendicular to the central axis. The first direction vector may optionally further include a vertical component. Angle A is measured between the radial direction and the two-dimensional vector formed by the radial and tangential components of the first direction vector.

[0017] The uniformity of fuel gas distribution is typically estimated using computational fluid dynamics simulations. By modeling the cylinder and gas supply system, the concentration of fuel gas in any volume of the combustion chamber at any point during the compression stroke can be estimated. The uniformity of fuel gas distribution at the end of the compression stroke can be determined by dividing the combustion chamber at the end of the compression stroke into N equal-sized volumes. For each of the N volumes, the concentration of fuel gas can be determined, thus forming the distribution. The uniformity of fuel gas distribution can then be determined using any suitable statistical measure (e.g., the standard deviation of the distribution). The distribution can be determined more precisely by increasing the value of N (thus decreasing the size of each volume). A suitable value of N can be found iteratively by increasing the value of N until the statistical measure (e.g., the standard deviation) reaches a substantially steady state.

[0018] The internal combustion engine is preferably a large, low-speed, turbocharged, two-stroke, single-flow scavenging crosshead internal combustion engine for propelling ships, with a power output of at least 400 kW per cylinder. The internal combustion engine may include a turbocharger driven by the exhaust gases produced by the internal combustion engine and configured to compress the scavenging gases. The internal combustion engine may be a dual-fuel engine having an Otto cycle mode when using fuel gas and a Diesel cycle mode when using alternative fuels (e.g., heavy fuel oil or marine diesel). This dual-fuel engine has its own dedicated fuel supply system for injecting alternative fuels, and this fuel supply system can also be used to inject pilot fuel in Otto cycle mode to ignite the mixture of fuel gas and scavenging gases.

[0019] Internal combustion engines may include dedicated ignition systems, such as ignition fuel systems, that inject a small amount of ignition fuel (e.g., heavy fuel oil or marine diesel). This ignition fuel is precisely measured so that only the amount needed to ignite the fuel gas and scavenging air mixture is used, ensuring that only the necessary amount of ignition fuel is employed. Compared to dedicated fuel supply systems for alternative fuels, such ignition fuel systems are much smaller in size and better suited for precisely injecting the amount of ignition fuel, which is unsuitable for this purpose due to the large size of their components.

[0020] Ignition fuel can be injected into a pre-combustion chamber, which is fluidly connected to the combustion chamber of the internal combustion engine. Alternatively, ignition fuel can be injected into a pre-combustion chamber group comprising multiple pre-combustion chambers (e.g., an inner pre-combustion chamber and an outer pre-combustion chamber). Alternatively, the mixture of fuel gas and scavenging air can be ignited by a device comprising a spark plug or a laser igniter. Each cylinder may have one or more scavenging air inlets at the bottom of the cylinder and an exhaust outlet at the top of the cylinder.

[0021] An EGR system may include an EGR receiver configured to draw in a certain amount of exhaust gas. As an example, the EGR receiver may draw in 10% to 60% or 30% to 50% of the exhaust gas. The EGR system may further include a pre-spray device configured to initially reduce the temperature of the exhaust gas. The EGR system may also include a cooling spray device configured to reduce the temperature of the exhaust gas. The cooling spray device may be arranged downstream of the pre-spray device. The EGR system may also include a water mist collector. The water mist collector may be arranged downstream of the cooling spray device. The EGR system may also include a blower configured to increase the pressure of the exhaust gas. The blower may be arranged downstream of the water mist collector. The blower may be configured to increase the pressure of the exhaust gas back to or slightly above the scavenging pressure. The EGR system may be configured to supply exhaust gas to the scavenging system.

[0022] In some embodiments, the first fuel gas valve is configured to inject fuel gas into the cylinder during the compression stroke at 0 to 160 degrees from the bottom dead center, at 0 to 130 degrees from the bottom dead center, or at 0 to 90 degrees from the bottom dead center.

[0023] Examples of fuel gases include natural gas, methane, ethane, liquefied petroleum gas, and ammonia.

[0024] In some embodiments, angle A is 5 to 35 degrees.

[0025] In some embodiments, the first fuel gas nozzle includes a first nozzle opening and a second nozzle opening, wherein fuel gas is permitted to enter the cylinder via the first nozzle opening along a first nozzle axis and via the second nozzle opening along a third nozzle axis, the third nozzle axis being angled relative to the radial direction in a direction opposite to the scavenging vortex direction.

[0026] In some embodiments, the fuel gas supply system further includes a second fuel gas valve for the cylinder, the second fuel gas valve being configured to allow fuel gas to enter the cylinder during the compression stroke via a second fuel gas nozzle at least partially disposed in the cylinder wall, such that the fuel gas can be mixed with scavenging gas from the scavenging inlet and the mixture of scavenging gas and fuel gas can be compressed before ignition, wherein, compared to the distribution of fuel gas in the cylinder caused by the second nozzle axis being at an angle B along the scavenging vortex direction, the distribution of fuel gas in the cylinder at the end of the compression stroke is less uniform due to the fuel gas being allowed to enter the cylinder via the second fuel gas valve along the second nozzle axis being at an angle B relative to the radial direction in a direction opposite to the scavenging vortex direction, thereby increasing the risk of premature ignition.

[0027] The axis of the second nozzle extends along a second direction vector. The second direction vector includes radial and tangential components arranged in a plane perpendicular to the central axis. Optionally, the second direction vector may further include a vertical component. Angle B is measured between the radial direction and the two-dimensional vector formed by the radial and tangential components of the second direction vector.

[0028] In some embodiments, the difference between angle A and angle B is less than 10 degrees or less than 5 degrees.

[0029] In some embodiments, the first fuel gas valve and the second fuel gas valve are arranged at approximately the same height in the cylinder.

[0030] If the height distance between the first fuel gas valve and the second fuel gas valve is less than 20% of the distance between the top dead center and the bottom dead center, less than 10% of the distance between the top dead center and the bottom dead center, or less than 5% of the distance between the top dead center and the bottom dead center, then the first fuel gas valve and the second fuel gas valve can be arranged at approximately the same height.

[0031] In some embodiments, the fuel gas supply system includes no more than two fuel gas valves.

[0032] In some embodiments, the first fuel gas valve is arranged substantially opposite to the second fuel gas valve.

[0033] According to a second aspect, the present invention relates to a two-stroke, single-flow scavenging crosshead internal combustion engine, comprising: at least one cylinder, a cylinder head, a piston, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system. The cylinder has cylinder walls, the cylinder head is disposed on the top of the cylinder and has an exhaust valve, the piston is movably disposed within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system has a scavenging inlet disposed at the bottom of the cylinder, the scavenging inlet being configured to permit scavenging, thereby forming a scavenging vortex rotating about the central axis, and the fuel gas supply system including a first scavenging inlet for the cylinder. A fuel gas valve, the first fuel gas valve being configured to allow fuel gas to enter the cylinder during the compression stroke via a first fuel gas nozzle arranged at least partially in the cylinder wall along a first nozzle axis, such that the fuel gas can be mixed with scavenging gas from the scavenging inlet and that the mixture of scavenging gas and fuel gas can be compressed prior to ignition, wherein the first nozzle axis is at an angle A relative to the radial direction in a direction opposite to the scavenging gas vortex direction, and wherein the engine further includes an exhaust gas recirculation (EGR) system configured to supply a certain amount of exhaust gas to the cylinder to address the risk of premature ignition.

[0034] In some embodiments, the fuel gas supply system and cylinder are designed such that if the axis of the first nozzle is arranged at an angle A along the direction of the scavenging vortex, the distribution of fuel gas in the cylinder is more uniform at the end of the compression stroke.

[0035] In some embodiments, the first fuel gas valve is configured to inject fuel gas into the cylinder during the compression stroke at 0 to 160 degrees from the bottom dead center, at 0 to 130 degrees from the bottom dead center, or at 0 to 90 degrees from the bottom dead center.

[0036] Examples of fuel gases include natural gas, methane, ethane, liquefied petroleum gas, and ammonia.

[0037] In some embodiments, the first fuel gas nozzle includes a first nozzle opening and a second nozzle opening, wherein fuel gas is permitted to enter the cylinder via the first nozzle opening along a first nozzle axis and via the second nozzle opening along a third nozzle axis, the third nozzle axis being angled relative to the radial direction in a direction opposite to the scavenging vortex direction.

[0038] In some embodiments, angle A is 5 to 35 degrees.

[0039] In some embodiments, the fuel gas supply system further includes a second fuel gas valve for the cylinder, the second fuel gas valve being configured to allow fuel gas to enter the cylinder during the compression stroke via a second fuel gas nozzle at least partially disposed in the cylinder wall, such that the fuel gas can be mixed with scavenging gas from the scavenging inlet and the mixture of scavenging gas and fuel gas can be compressed prior to ignition, wherein the fuel gas is allowed to enter the cylinder via the second fuel gas valve along the axis of a second nozzle, the axis of the second nozzle being at an angle B relative to the radial direction in a direction opposite to the direction of the scavenging gas vortex.

[0040] In some embodiments, the difference between angle A and angle B is less than 10 degrees or less than 5 degrees.

[0041] In some embodiments, the fuel gas supply system and cylinder are designed such that if the second nozzle axis is arranged at an angle B along the direction of the scavenging vortex, the distribution of fuel gas in the cylinder is more uniform at the end of the compression stroke.

[0042] In some embodiments, the first fuel gas valve and the second fuel gas valve are arranged at approximately the same height in the cylinder.

[0043] If the height distance between the first fuel gas valve and the second fuel gas valve is less than 20% of the distance between the top dead center and the bottom dead center, less than 10% of the distance between the top dead center and the bottom dead center, or less than 5% of the distance between the top dead center and the bottom dead center, then the first fuel gas valve and the second fuel gas valve can be arranged at approximately the same height.

[0044] In some embodiments, the first fuel gas valve is arranged substantially opposite to the second fuel gas valve.

[0045] In some embodiments, the fuel gas supply system includes no more than two fuel gas valves.

[0046] Different aspects of the invention can be implemented in various ways, including a method for allowing fuel gas to enter a two-stroke single-flow scavenging crosshead internal combustion engine as described in the context, and a two-stroke single-flow scavenging crosshead internal combustion engine, each producing one or more of the benefits and advantages described in connection with at least one aspect described above, and each having one or more preferred embodiments corresponding to the preferred embodiments described in connection with at least one aspect described above and / or disclosed in the dependent claims. Furthermore, it will be understood that embodiments described in connection with one of the aspects described herein can be equally applied to the other aspects. Attached Figure Description

[0047] The above and / or additional objects, features, and advantages of the invention will be further illustrated by the following illustrative and non-limiting detailed description of embodiments of the invention with reference to the accompanying drawings, in which:

[0048] Figure 1 A cross section of a two-stroke, single-flow scavenging crosshead internal combustion engine according to an embodiment of the present invention is shown schematically.

[0049] Figure 2 The cross-section of a cylinder of a two-stroke, single-flow scavenging crosshead internal combustion engine according to an embodiment of the present invention is shown schematically.

[0050] Figures 3a to 3b It shows Figure 2 A close-up of a part.

[0051] Figures 4a to 4b The cross-section of a cylinder of a two-stroke, single-flow scavenging crosshead internal combustion engine according to an embodiment of the present invention is shown schematically. Detailed Implementation

[0052] In the following description, reference is made to the accompanying drawings, which illustrate by way of showing how the invention can be practiced.

[0053] Figure 1A cross-section of a two-stroke, single-flow scavenging crosshead internal combustion engine 100 for propelling a ship, according to an embodiment of the present invention, is shown schematically. The two-stroke internal combustion engine 100 includes a scavenging system 111, an exhaust gas receiver 108, and a turbocharger 109. The two-stroke internal combustion engine has a plurality of cylinders 101 (only a single cylinder is shown in the cross-section). Each cylinder 101 includes a scavenging inlet 102 disposed at the bottom of the cylinder and configured to permit scavenging, thereby forming a scavenging vortex 120 rotating about a central axis 114. Each cylinder further includes: a piston 103; a cylinder head 113 disposed on top of the cylinder; an exhaust valve 104 disposed in the cylinder head 113; and a first fuel gas valve 105 (illustrated schematically only). 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). Piston 103 is movably arranged within the cylinder between bottom dead center and top dead center along central axis 114. A first fuel gas valve 105 is configured to allow fuel gas to enter cylinder 101 during the compression stroke via a first fuel gas nozzle along a first nozzle axis (not shown), such that the fuel gas can be mixed with scavenging gas from scavenging inlet 102 and that the mixture of scavenging gas and fuel gas is compressed prior to ignition. The first fuel gas nozzle is at least partially arranged in the cylinder wall between cylinder head 113 and scavenging inlet 102. The first nozzle axis forms an angle A relative to the radial direction in a direction opposite to the scavenging swirl direction 120. The engine further includes an exhaust gas recirculation (EGR) system 130. The engine further includes a dedicated ignition system 115, such as an ignition fuel system capable of injecting a small amount of ignition fuel (e.g., heavy fuel oil or marine diesel). Ignition fuel can be injected into a pre-combustion chamber fluidly connected to the combustion chamber of the internal combustion engine. Alternatively, ignition fuel can be injected into a pre-combustion chamber group comprising multiple pre-combustion chambers (e.g., an inner pre-combustion chamber and an outer pre-combustion chamber). Alternatively, a dedicated ignition system 115 can ignite the fuel gas and scavenging gas mixture using a device including a spark plug or laser igniter optionally arranged in the pre-combustion chamber group. Each cylinder may have one or more scavenging gas inlets at the bottom of the cylinder and an exhaust outlet at the top of the cylinder.

[0054] The fuel gas supply system and cylinder 101 can be designed such that if the first nozzle axis is arranged at angle A along the direction of the scavenging swirl 120, the distribution of fuel gas within cylinder 101 is more uniform at the end of the compression stroke. Therefore, by arranging the nozzle axis in the direction opposite to the scavenging swirl direction 120, the risk of premature ignition increases. However, the increased risk of premature ignition can be effectively addressed using an EGR system 130. As an example, the amount of exhaust gas recirculation using the EGR system 130 can be slightly increased compared to the amount of exhaust gas recirculation when the first nozzle axis is arranged at angle A along the direction of the scavenging swirl.

[0055] It has been found that by injecting fuel gas in a manner that makes the distribution of fuel gas less uniform and simultaneously using EGR to address the increased risk of premature ignition, fuel consumption has been improved, heat load on components has been reduced, and emissions have been lowered.

[0056] Figure 2 A cross-section of cylinder 201 of a two-stroke, single-flow scavenging crosshead internal combustion engine according to an embodiment of the present invention is shown schematically. Figure 3a It shows Figure 2 A close-up of the upper part. Figure 3b It shows Figure 2 A close-up of the lower portion. The engine includes a fuel gas supply system comprising a first fuel gas valve 204 and a second fuel gas valve 206, at least partially disposed within the cylinder wall. The first fuel gas valve 204 is configured to allow fuel gas to enter the cylinder 201 via a first fuel gas nozzle 208 during the compression stroke, and the second fuel gas valve 206 is configured to allow fuel gas to enter the cylinder via a second fuel gas nozzle 209 during the compression stroke, thereby enabling the fuel gas to mix with scavenging air from the scavenging inlet and allowing the mixture of scavenging air and fuel gas to be compressed before ignition. Fuel gas is allowed to enter the cylinder via the first fuel gas valve 204 along a first nozzle axis 205, which is at an angle A relative to the radial direction in a direction opposite to the scavenging swirl direction 202. The first nozzle axis 205 extends along a first direction vector. The first direction vector includes a plane disposed perpendicular to the central axis of the cylinder 201. Figure 2 and Figures 3a to 3bThe first direction vector (in the plane) contains radial components 211 and tangential components 210. Optionally, the first direction vector may further include a vertical component. Angle A is measured between the radial direction and a two-dimensional vector 212 formed by the radial and tangential components 211 and 210 of the first direction vector. Fuel gas is permitted to enter the cylinder via a second fuel gas valve 206 along a second nozzle axis 207, which is at an angle B relative to the radial direction 211 in a direction opposite to the scavenging swirl direction 202. Compared to the fuel gas distribution within the cylinder caused by the first nozzle axis 205 and the second nozzle axis 207 being at an angle A / B along the scavenging swirl direction 202, making the first nozzle axis 205 and the second nozzle axis 207 at an angle A / B in a direction opposite to the scavenging swirl direction 202 results in a less uniform fuel gas distribution within the cylinder at the end of the compression stroke.

[0057] The second nozzle axis 205 extends along a second direction vector. The second direction vector includes a radial component 214 and a tangential component 213 arranged in a plane perpendicular to the central axis of the cylinder 201. The second direction vector may optionally further include a vertical component. Angle B is measured between the radial direction and a two-dimensional vector 215 formed by the radial component 214 and the tangential component 213 of the second direction vector.

[0058] Figure 4a A cross-section of a cylinder of a two-stroke, single-flow scavenging crosshead internal combustion engine according to an embodiment of the present invention is schematically shown. A first fuel gas nozzle 409 for allowing fuel gas to enter the cylinder during the compression stroke is shown. The first fuel gas nozzle 409 includes a main nozzle passage 494 and an auxiliary nozzle passage 493. The main nozzle passage 494 has a first nozzle opening 490, and the auxiliary nozzle passage 493 has a second nozzle opening 492. Fuel gas is allowed to enter the cylinder via the first nozzle opening 490 along a first nozzle axis 405 and via the second nozzle opening 492 along a third nozzle axis 491. Both the first nozzle axis 405 and the second nozzle axis 491 are angled relative to the radial direction in a direction opposite to the scavenging swirl direction 402.

[0059] Figure 4bA cross-section of a cylinder of a two-stroke, single-flow scavenging crosshead internal combustion engine according to an embodiment of the present invention is schematically shown. A first fuel gas nozzle 409 for allowing fuel gas to enter the cylinder during the compression stroke is shown. The first fuel gas nozzle 409 includes a main nozzle passage 494 and an auxiliary nozzle passage 493. The main nozzle passage 494 has a first nozzle opening 490, and the auxiliary nozzle passage 493 has a second nozzle opening 492. Fuel gas is allowed to enter the cylinder via the first nozzle opening 490 along a first nozzle axis 405 and via the second nozzle opening 492 along a third nozzle axis 491. The first nozzle axis 405 is angled relative to the radial direction in a direction opposite to the scavenging swirl direction 402, and the third nozzle axis 491 is angled in a direction along the scavenging swirl direction 402.

[0060] By equipping the fuel gas nozzle with an auxiliary nozzle channel (in addition to the main nozzle channel), there are more possibilities for providing the desired mixture of fuel gas and scavenging air, thereby further optimizing fuel economy and emission characteristics.

[0061] While some embodiments have been described in detail and illustrated, the invention is not limited thereto, but can be practiced in other ways within the scope of the subject matter defined in the appended claims. Specifically, it should be understood that other embodiments can be utilized and structural and functional changes can be made without departing from the scope of the invention.

[0062] In an apparatus claim that enumerates several means, some of these means may be implemented by one and the same hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that combinations of these measures cannot be advantageously used.

[0063] It should be emphasized that, when used in this specification, the term "comprises" is used to indicate the presence of a stated feature, integral, step, or component, but does not exclude the presence or addition of one or more other features, integrals, steps, components, or groups thereof.

Claims

1. A method for allowing fuel gas to enter a two-stroke single-flow scavenging crosshead internal combustion engine (100), the two-stroke single-flow scavenging crosshead internal combustion engine comprising at least one cylinder (101), a cylinder head (113), a piston (103), a fuel gas supply system connectable to a fuel gas tank, and a scavenging system (111), the cylinder (101) having cylinder walls, the cylinder head (113) disposed on top of the cylinder (101) and having an exhaust valve (104), the piston (103) being movably disposed within the cylinder (101) along a central axis (114) between bottom dead center and top dead center, the scavenging system (111) having a scavenging system disposed within the cylinder. (101) has scavenging inlets (102) at the bottom, which are configured to allow scavenging gas to enter the cylinder (101), thereby forming a scavenging vortex (120) rotating about the central axis (114). The fuel gas supply system includes a first fuel gas valve (105, 204) for the cylinder (101), which is configured to allow fuel gas to enter the cylinder (101) during the compression stroke via a first fuel gas nozzle (208) arranged at least partially in the cylinder wall, such that the fuel gas can be mixed with the scavenging gas from the scavenging inlets (102) and the mixture of scavenging gas and fuel gas can be compressed before ignition. Fuel gas is permitted to enter the cylinder (101) via the first fuel gas valve (105, 204) along the first nozzle axis (205), the first nozzle axis being at an angle A relative to the radial direction (211) in a direction opposite to the scavenging vortex direction (202), wherein an exhaust gas recirculation (EGR) system (130) is used to supply a certain amount of exhaust gas to the cylinder (101) to address the increased risk of premature ignition.

2. The method according to claim 1, wherein, The fuel gas supply system further includes a second fuel gas valve (206) for the cylinder (101), the second fuel gas valve being configured to allow fuel gas to enter the cylinder (101) during the compression stroke via a second fuel gas nozzle (209) arranged at least partially in the cylinder wall, such that the fuel gas can be mixed with scavenging gas from the scavenging inlet (102) and the mixture of scavenging gas and fuel gas can be compressed before ignition, wherein the fuel gas is allowed to enter the cylinder (101) via the second fuel gas valve (206) along the axis (207) of the second nozzle, the axis of the second nozzle being at an angle B relative to the radial direction (211) in a direction opposite to the scavenging vortex direction (202).

3. The method according to claim 2, wherein, The first fuel gas valve (105, 204) and the second fuel gas valve (206) are arranged at approximately the same height in the cylinder (101).

4. The method according to claim 3, wherein, The first fuel gas valve (105, 204) is arranged substantially opposite the second fuel gas valve (206).

5. The method according to claim 1 or 2, wherein, The first fuel gas nozzle (208) includes a first nozzle opening (490) and a second nozzle opening (492), through which fuel gas is permitted to enter the cylinder (101) along the first nozzle axis (205) via the first nozzle opening (490) and along the third nozzle axis (491) via the second nozzle opening (492), the third nozzle axis being angled relative to the radial direction (211) in a direction opposite to the scavenging vortex direction (202).

6. A two-stroke, single-flow scavenging crosshead internal combustion engine (100), comprising at least one cylinder (101), a cylinder head (113), a piston (103), a fuel gas supply system connectable to a fuel gas tank, and a scavenging system (111), the cylinder (101) having cylinder walls, the cylinder head (113) disposed on top of the cylinder (101) and having an exhaust valve (104), the piston (103) being movably disposed within the cylinder (101) along a central axis (114) between bottom dead center and top dead center, and the scavenging system (111) having a scavenging inlet (104) disposed at the bottom of the cylinder (101). 02), these scavenging inlets are configured to allow scavenging, thereby forming a scavenging vortex (120) rotating about the central axis (114), the fuel gas supply system including a first fuel gas valve (105, 204) for the cylinder (101), the first fuel gas valve being configured to allow fuel gas to enter the cylinder (101) during the compression stroke via a first fuel gas nozzle (208) arranged at least partially in the cylinder wall along the first nozzle axis (205), such that the fuel gas can be mixed with the scavenging gas from the scavenging inlet (102) and allow the mixture of scavenging gas and fuel gas to be compressed before ignition, characterized in that, The first nozzle axis (205) is at an angle A relative to the radial direction (211) in a direction opposite to the scavenging vortex direction (202), and wherein the engine (100) further includes an exhaust gas recirculation (EGR) system (130) configured to supply a certain amount of exhaust gas to the cylinder (101) to address the risk of premature ignition.

7. The two-stroke, single-flow scavenging crosshead internal combustion engine (100) according to claim 6, wherein, The fuel gas supply system further includes a second fuel gas valve (206) for the cylinder (101), the second fuel gas valve being configured to allow fuel gas to enter the cylinder (101) during the compression stroke via a second fuel gas nozzle (209) arranged at least partially in the cylinder wall, such that the fuel gas can be mixed with scavenging gas from the scavenging inlet (102) and the mixture of scavenging gas and fuel gas can be compressed before ignition, wherein the fuel gas is allowed to enter the cylinder (101) via the second fuel gas valve (206) along the axis (207) of the second nozzle, the axis of the second nozzle being at an angle B relative to the radial direction (211) in a direction opposite to the scavenging vortex direction (202).

8. The two-stroke, single-flow scavenging crosshead internal combustion engine (100) according to claim 7, wherein, The first fuel gas valve (105, 204) and the second fuel gas valve (206) are arranged at approximately the same height in the cylinder (101).

9. The two-stroke, single-flow scavenging crosshead internal combustion engine (100) according to claim 8, wherein, The first fuel gas valve (105, 204) is arranged substantially opposite the second fuel gas valve (206).

10. The two-stroke, single-flow scavenging crosshead internal combustion engine (100) according to any one of claims 6 to 9, wherein, The first fuel gas nozzle (208) includes a first nozzle opening (490) and a second nozzle opening (492), through which fuel gas is permitted to enter the cylinder along the first nozzle axis (205) via the first nozzle opening (490) and along the third nozzle axis (491) via the second nozzle opening (492), the third nozzle axis being angled relative to the radial direction (211) in a direction opposite to the scavenging vortex direction (202).

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