Internal combustion engine

Abstract

To provide a two-stroke uniflow scavenging cross head internal combustion engine including at least one cylinder, a cylinder cover, a piston, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system.SOLUTION: A fuel gas supply system includes a first fuel gas valve constituted to allow a fuel gas to enter a main combustion chamber defined between a piston and a cylinder cover during a compression stroke to the cylinder via a fuel gas nozzle. The first fuel gas valve is at least partially disposed in the cylinder cover, a nozzle of the first fuel gas valve has a first nozzle opening constituted to inject the fuel gas along a first nozzle shaft, and the first nozzle shaft forms an angle with respect to an axial direction.SELECTED DRAWING: Figure 3a

Description

Technical Field

[0001] The present invention relates to a two-stroke internal combustion engine.

Background Art

[0002] Two-stroke internal combustion engines are used as propulsion devices in ships such as container ships, bulk carriers and tankers. Reduction of unnecessary exhaust gas from internal combustion engines is becoming increasingly important.

[0003] An effective method for reducing the amount of unnecessary exhaust gas is to switch from fuel oil, for example heavy fuel oil (HFO), to fuel gas. The fuel gas may be injected into the cylinder at the end of the compression stroke, and can be ignited immediately by the high temperature achieved by the gas in the cylinder when compressed, or by ignition of a pilot fuel. However, injecting fuel gas into the cylinder at the end of the compression stroke requires a high-pressure gas compressor for compressing the fuel gas before injection, to overcome the high pressure in the cylinder.

[0004] However, high-pressure gas compressors are expensive and complex to manufacture and maintain. One method for avoiding the need for a high-pressure compressor is to provide a fuel gas valve configured to inject fuel gas at the beginning of the compression stroke, when the pressure in the cylinder is significantly lower.

[0005] DK176118B discloses such an engine, in which gas is injected into the scavenge inlet or directly into the cylinder through the cylinder wall.

[0006] WO2013007863 discloses another example of such an engine, in which gas is injected directly into the cylinder through the cylinder wall.

[0007] It may be difficult to ensure fast and efficient mixing between scavenge gas and fuel gas in the cylinder.

[0008] An imhospitalized mixture of fuel gas and scavenging gas may result in incomplete combustion of the fuel gas, or even knocking due to premature ignition.

[0009] Therefore, improving the mixture of fuel gas and scavenging gas in the cylinder remains a problem. [Overview of the Initiative]

[0010] In a first aspect, the present invention relates to a two-stroke uniflow scavenging crosshead internal combustion engine, the two-stroke uniflow scavenging crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system, wherein the cylinder has a cylinder wall, the cylinder cover is located at the upper end of the cylinder and has an exhaust valve, the piston is positioned to move within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system has a scavenging inlet located at the bottom of the cylinder, and the fuel gas supply system comprises a first fuel gas valve configured to allow fuel gas to enter a main combustion chamber defined between the piston and the cylinder cover during a compression stroke via a fuel gas nozzle that enables mixing fuel gas with scavenging from the scavenging inlet and compressing the mixture of scavenging and fuel gas before ignition, the first fuel gas valve is at least partially located in the cylinder cover, and the nozzle of the first fuel gas valve has a first nozzle opening configured to inject fuel gas along a first nozzle axis, the first nozzle axis being at an angle to the axial direction.

[0011] As a result, by positioning the fuel gas valve inside the cylinder cover and angling the fuel gas nozzle to the axial direction, the resulting fuel gas jet collides with a large portion of the cylinder wall, resulting in a homogeneous mixture of fuel gas and scavenging gas.

[0012] The internal combustion engine is preferably a large, low-speed, turbocharged, two-stroke crosshead internal combustion engine with uniflow scavenging for propelling a vessel having at least 400 kW of power per cylinder. The internal combustion engine may also include a turbocharger that is driven by the exhaust gases produced by the internal combustion engine and configured to compress the scavenging. The internal combustion engine may also be a dual-fuel engine having an Otto cycle mode when fueled by fuel gas and a diesel cycle mode when fueled by an alternative fuel, such as heavy oil or marine diesel oil. Such a dual-fuel engine has its own dedicated fuel supply system for injecting the alternative fuel, which may also be used for injecting pilot fuel when operating in Otto cycle mode for igniting the mixture of fuel gas and scavenging.

[0013] An internal combustion engine may be equipped with a dedicated ignition system, such as a pilot fuel system, capable of injecting a precisely measured small amount of pilot fuel, for example, heavy fuel oil or marine diesel oil, so that it can ignite just the right amount of the fuel gas-scavenging mixture to use only the required amount of pilot fuel. Such a pilot fuel system is smaller in size and better suited to injecting precise amounts of pilot fuel compared to a dedicated fuel supply system for alternative fuels, because the larger size of the components is not suitable for this purpose.

[0014] The pilot fuel may be injected in a preheating chamber that is fluidly connected to the combustion chamber of the internal combustion engine. Alternatively, the mixture of fuel gas and scavenging may be ignited by means of a spark plug or laser igniter. Each cylinder may have one or more scavenging inlets at the bottom of the cylinder and an exhaust port at the top of the cylinder.

[0015] The fuel gas supply system is preferably configured to inject fuel gas through one or more fuel gas valves under sonic conditions, i.e., at a constant speed equal to the speed of sound. Sonic conditions may be achieved when the pressure drop ratio across the nozzle throat (minimum cross-sectional area) is approximately greater than 2.

[0016] The central axis extends axially. The entire first fuel gas valve may be located within the cylinder cover. Alternatively, only a portion of the first fuel gas valve may be located within the cylinder cover; for example, the nozzle may be located within the cylinder cover, while the remaining portion of the fuel gas valve is located outside the cylinder cover. However, a portion of the fuel gas nozzle may also be located outside the cylinder cover; for example, the distal end of the fuel gas nozzle may protrude into the main combustion chamber, as will be further described below. The nozzle of the first fuel gas valve may have a distal portion extending along the first nozzle axis; for example, the distal portion may have a tubular shape with the first nozzle axis centered.

[0017] In some embodiments, the angle between the first nozzle axis and the axial direction is between 5 and 50 degrees, between 10 and 40 degrees, or between 15 and 30 degrees.

[0018] Examples of fuel gases include natural gas, methane, ethane, liquefied petroleum gas, and ammonia.

[0019] In some embodiments, the cylinder has a first and a second portion separated by a reference plane extending along a central axis, at least a portion of the nozzle of a first fuel gas valve is located in a cylinder cover above the first portion of the cylinder, and the first nozzle shaft has an upper portion extending into the first portion of the cylinder and a lower portion extending into the second portion of the cylinder.

[0020] As a result, by having a first fuel gas valve positioned above a first portion of the cylinder and configured to inject fuel gas toward a second portion of the cylinder, the resulting fuel gas jet strikes the cylinder wall in a high radial motion, which can help distribute the fuel gas through the main combustion chamber.

[0021] The first and second parts of the cylinder may be of equal size. The first nozzle shaft has a radial component and an axial component, and the reference plane is positioned perpendicular to the radial component of the first nozzle shaft. The first nozzle shaft may optionally also have a connecting component.

[0022] In some embodiments, the piston at bottom dead center is positioned below both the upper and lower parts of the first nozzle shaft, the piston at top dead center is positioned above the entire lower part of the first nozzle shaft, and the first fuel gas valve is configured to initiate fuel gas injection during the previous compression stroke when the piston is above the entire lower part of the first nozzle shaft.

[0023] Therefore, the resulting jet of fuel gas can strike the cylinder wall before the piston moves, during the compression stroke, which prevents access to that portion of the cylinder wall.

[0024] The first fuel gas valve may be configured to initiate fuel gas injection during the compression stroke before the piston reaches the bottom of the first nozzle shaft. The first fuel gas valve may inject fuel gas for an injection period, which ends before the piston is above the entire bottom of the first nozzle shaft.

[0025] In some embodiments, the fuel gas supply system comprises a second fuel gas valve having a fuel gas nozzle relative to a cylinder, the second fuel gas valve being at least partially located within the cylinder cover, and the nozzle of the second fuel gas valve having a first nozzle opening configured to inject fuel gas along a second nozzle axis, the second nozzle axis being at an angle with respect to the axial direction.

[0026] The second fuel gas valve may correspond to the first fuel gas valve.

[0027] In some embodiments, at least a portion of the nozzle of the second fuel gas valve is disposed in the cylinder cover above the second portion of the cylinder, and the second nozzle axis has an upper portion extending into the second portion of the cylinder and a lower portion extending into the first portion of the cylinder.

[0028] As a result, providing a first fuel gas valve arranged on the first portion of the cylinder for directing fuel gas towards the second portion of the cylinder and a second fuel gas valve arranged on the second portion of the cylinder for directing fuel gas towards the first portion of the cylinder enables particularly effective mixing of fuel gas and scavenging gas.

[0029] In some embodiments, the piston at bottom dead center is arranged below both the upper portion and the lower portion of the second nozzle axis, the piston at top dead center is arranged above the entire lower portion of the second nozzle axis, and the second fuel gas valve is configured to start injecting fuel gas during the compression stroke before the piston moves above the entire lower portion of the second nozzle axis.

[0030] The second fuel gas valve may be configured to start injecting fuel gas during the compression stroke before the piston reaches the lower portion of the second nozzle axis. The second fuel gas valve may inject fuel gas during an injection period, and the injection period ends before the piston moves above the entire lower portion of the second nozzle axis.

[0031] In some embodiments, the first nozzle axis intersects the second nozzle axis.

[0032] As a result, the jet stream generated from the first fuel gas valve collides with the jet stream generated from the second fuel gas valve, thereby achieving improved mixing of fuel gas and scavenging gas.

[0033] In some embodiments, the first fuel gas valve is configured to begin injecting fuel gas before closing the exhaust valve.

[0034] The applicant has found that if the fuel gas exiting the fuel gas nozzle has sufficiently high kinetic energy, it is possible to initiate fuel gas injection long before the exhaust valve closes, without causing significant direct leakage of fuel gas through the exhaust valve. High kinetic energy of the fuel gas may be achieved by ensuring that the fuel gas is injected under sonic conditions and by using a nozzle with a large throat.

[0035] In some embodiments, the engine has a stroke of X mm, and the first nozzle opening of the nozzle of the first fuel gas valve has a diameter of Y, where Y is between 1% and 4% of X.

[0036] As a result, by using nozzles with a diameter of 1% to 4% of the hole size (which is a large diameter), it is ensured that the fuel gas is injected at high velocity.

[0037] In some embodiments, the first fuel gas valve is configured to begin injecting fuel gas 95 degrees, 90 degrees, or 85 degrees before bottom dead center.

[0038] As a result, initiating injection earlier provides more opportunities for the fuel gas to mix with the scavenging gas.

[0039] In some embodiments, the first fuel gas valve is configured to begin injecting fuel gas 40 degrees, 50 degrees, or 60 degrees after bottom dead center.

[0040] As a result, it can be ensured that fuel gas does not leak directly from the open exhaust valve, or that only a small amount of fuel gas is allowed.

[0041] In some embodiments, the nozzle of the first fuel gas valve protrudes into the main combustion chamber, and the first fuel gas valve is configured to begin injecting fuel gas before the exhaust valve is closed.

[0042] As a result, fuel gas injection may be initiated earlier without causing increased direct gas leakage through the exhaust valve.

[0043] In some embodiments, the exhaust valve has a valve plate which is movable along a central axis between a closed position and an open position, and the exhaust valve plate is positioned at a first height in the closed position and a second height in the open position, the first height being higher than the second height, and the distal end of the nozzle is positioned below the second height, i.e., below the height of the exhaust valve when the exhaust valve is open.

[0044] In some embodiments, the exhaust valve has a valve plate which is movable along the exhaust valve axis between a closed position and an open position, the center of the first nozzle opening is located at a first distance from the central axis, and the center of the valve plate of the exhaust valve is located at a second distance from the central axis, the second distance being longer than the first distance.

[0045] As a result, by positioning the exhaust valves with different centers, the first fuel gas valve can accommodate more central positions within the cylinder cover. This allows the ignition system to be positioned more centrally, for example, in the preheating chamber, or a preheating chamber set with central exhaust can be positioned.

[0046] The exhaust valve shaft may be parallel to the central axis, so that the distance from the center of the valve plate to the central axis corresponds to the distance between the central axis and the exhaust valve shaft. The cylinder cover may have multiple exhaust valves with different centers, for example, at least two, at least three, or at least four exhaust valves with different centers. The first distance may be less than 25% of the cylinder's inner diameter.

[0047] In some embodiments, the fuel gas valve is configured to inject fuel gas for an injection period, which is shorter than the time it takes to rotate the crank angle by 30 degrees.

[0048] In some embodiments, the first fuel gas valve has a second nozzle opening configured to inject fuel gas along a third nozzle axis, the third nozzle axis being at an angle to the axial direction, and the angle between the third nozzle axis and the axial direction is greater than the angle between the first nozzle axis and the axial direction.

[0049] As a result, the second nozzle opening ensures that the fuel gas is supplied to the upper part of the main combustion chamber, thereby achieving better distribution of the fuel gas.

[0050] Different aspects of the present invention can be realized in different ways, including two-stroke uniflow scavenging crosshead internal combustion engines as described above and as follows, each resulting in one or more of the benefits and advantages described in relation to at least one of the above aspects, and each having one or more preferred embodiments corresponding to the preferred embodiments described in relation to at least one of the above aspects and / or disclosed in the dependent claims. Furthermore, it will be understood that embodiments described in relation to one of the aspects described herein can be equally applied to the other aspects.

[0051] The above and / or additional objects, features and advantages of the present invention will be further elucidated by the following exemplary and non-limiting detailed description of embodiments of the present invention with reference to the accompanying drawings. [Brief explanation of the drawing]

[0052] [Figure 1] Figure 1 schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. [Figure 2] Figure 2 schematically shows a cross-section of a fuel gas valve for a two-stroke internal combustion engine according to an embodiment of the present invention. [Figure 3a] Figure 3a schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. [Figure 3b] Figure 3b schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. [Figure 3c] Figure 3c schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. [Figure 4] Figure 4 schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. [Figure 5] Figure 5 schematically shows the upper end of a cylinder equipped with a cylinder cover according to an embodiment of the present invention. [Figure 6] Figure 6 schematically illustrates a fuel gas valve according to an embodiment of the present invention. [Modes for carrying out the invention]

[0053] The following description will refer to the accompanying drawings which illustrate how the present invention can be implemented.

[0054] Figure 1 schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine 100 for propelling a ship, according to an embodiment of the present invention. The two-stroke internal combustion engine 100 comprises 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 one cylinder is shown in the cross-section). Each cylinder 101 comprises a scavenging inlet 102 located in the lower section of the cylinder to provide scavenging, a piston 103, a cylinder cover 112 located at the upper end of the cylinder, an exhaust valve 104 located on the cylinder cover, and one or more fuel gas valves 105 (illustrated schematically only). The scavenging inlet 102 is fluidly connected to the scavenging 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 piston 103 is movably positioned within the cylinder along a central axis 113 between bottom dead center and top dead center. The central shaft 113 extends axially. The fuel gas valve 105 is configured to introduce fuel gas into a main combustion chamber defined between the piston 103 and the cylinder cover 112 during the compression stroke, via a fuel gas nozzle (not shown) that allows the fuel gas to be mixed with the scavenging gas. The fuel gas valve 105 is at least partially located in the cylinder cover 112, and the nozzle of the fuel gas valve has a first nozzle opening (not shown) configured to inject fuel gas along a first nozzle axis 150. The first nozzle axis 150 is at an angle with respect to the axial direction. As a result of positioning the fuel gas valve 105 in the cylinder cover 120 and the fuel gas nozzle being at an angle with respect to the axial direction, the resulting fuel gas jets collide with a large portion of the cylinder wall, resulting in a homogeneous mixture of fuel gas and scavenging gas.

[0055] The internal combustion engine 100 is equipped with a dedicated ignition system 116 for igniting the fuel gas-scavenging mixture at the end of the compression stroke. For example, the dedicated ignition system may be a pilot fuel system capable of injecting a precisely measured small amount of pilot fuel, such as heavy oil or marine diesel oil, so that just the right amount of the fuel gas-scavenging mixture is ignited so that only the required amount of pilot fuel is used. Such a pilot fuel system is smaller in size and better suited to injecting the appropriate amount of pilot fuel compared to a dedicated fuel supply system for alternative fuels, because the larger size of the components is not suitable for this purpose. The pilot fuel may be injected in a preheating chamber that is fluidly connected to the combustion chamber of the internal combustion engine. Alternatively, the pilot fuel may be injected in a set of preheating chambers that are fluidly connected to the combustion chamber of the internal combustion engine. The fuel gas valve 105 may be configured to begin injecting fuel gas 95 degrees, 90 degrees, or 85 degrees before bottom dead center. The first fuel gas valve may be configured to start injecting fuel gas 40 degrees, 50 degrees, or 60 degrees after bottom dead center.

[0056] The scavenging system 111 comprises a scavenging receiver 110 and an air cooler 106. The exhaust valve is located in the center of the cylinder cover, and the timing of the exhaust valve can be made variable so that, for example, the closing and opening of the exhaust valve can be optimized to control the compression ratio and / or temperature in the cylinder.

[0057] Figure 2 schematically shows a cross-section of a fuel gas valve 200 for a two-stroke internal combustion engine according to an embodiment of the present invention. The fuel gas valve 200 in the figure is shown in a horizontal position, but may be positioned at any angle with respect to the axial direction. The fuel gas valve 200 comprises a valve shaft 201, a valve plate 202, a valve seat 203, and a fuel gas nozzle 204 having a first nozzle opening 206. The fuel gas valve 200 shown has a single nozzle opening, but may have multiple nozzle openings. The valve shaft 201 and valve plate 202 are movable between a closed position, which prevents fuel gas from flowing through the fuel gas valve 200, and an open position, which allows fuel gas to flow through the fuel gas valve 200. The valve shaft 201 and valve plate 202 are shown in the closed position in Figure 2. The valve shaft 201 and valve plate 202 are movable between the closed and open positions by an actuator (not shown) controlled by a control unit (not shown). The first nozzle opening 206 is configured to inject fuel gas along the first nozzle axis 205.

[0058] Figures 3a-3c schematically show cross-sections of a two-stroke uniflow scavenging crosshead internal combustion engine according to embodiments of the present invention, where Figure 3a shows the engine with the piston at bottom dead center, Figure 3b shows the engine with the piston in the middle of the compression stroke, and Figure 3c shows the engine with the piston at top dead center. The two-stroke uniflow scavenging crosshead internal combustion engine comprises at least one cylinder 115, a cylinder cover 112, a piston 103, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system (not shown). The cylinder has a cylinder wall, the cylinder cover 112 is located at the upper end of the cylinder 115 and has an exhaust valve 104, and the piston 103 is movably positioned within the cylinder 115 along a central axis 113 between bottom dead center and top dead center. The central axis 113 extends axially. A scavenging system having a scavenging inlet 102 is located at the bottom of the cylinder 115, and the fuel gas supply system includes a first fuel gas valve 105 configured to allow fuel gas to enter a main combustion chamber defined between the piston 103 and the cylinder cover 112 during the compression stroke, via a fuel gas nozzle that allows fuel gas to be mixed with scavenging from the scavenging inlet 102 and to compress the mixture of scavenging and fuel gas before ignition. The first fuel gas valve 105 is at least partially located in the cylinder cover 112. The nozzle of the first fuel gas valve 105 has a first nozzle opening configured to inject fuel gas along a first nozzle axis 150. The first nozzle axis 150 is at an angle 157 with respect to the axial and central axes. In this embodiment, the angle is approximately 22 degrees. However, in other embodiments, the angle between the first nozzle axis and the axial axis is between 5 and 50 degrees, between 10 and 40 degrees, or between 15 and 30 degrees. The first nozzle shaft 150 has a radial component 155 and an axial component 156. The cylinder 115 has a first part 160 and a second part 161, which are separated by a reference plane 151 extending along the central axis 113. The reference plane 151 is positioned perpendicular to the radial component 155 of the first nozzle shaft 150, i.e., the reference plane 151 is also perpendicular to the plane of the drawing.The nozzle of the first fuel gas valve 150 is located in the cylinder cover 112 above the first portion of the cylinder 160, and the first nozzle shaft 150 has an upper part 170 extending into the first portion of the cylinder (inside the cylinder) and a lower part 171 extending into the second portion of the cylinder (inside the cylinder). At bottom dead center, the piston 103 is located below both the upper part 170 and the lower part 171 of the first nozzle shaft 150 (see Figure 3a), and at top dead center, the piston 103 is located above the entire lower part 171 of the first nozzle shaft 150 (see Figure 3c). The first fuel gas valve 105 is configured to initiate fuel gas injection during the compression stroke before the piston 103 reaches the lower part 171 of the first nozzle shaft, i.e., before the piston 103 reaches the piston shown in Figure 3b. As a result, having a first fuel gas positioned above the first part of the cylinder and configured to inject the fuel gas toward the second part of the cylinder, the resulting fuel gas jet can impact the cylinder wall with a high radial motion that helps in the distribution of the fuel gas through the main combustion chamber.

[0059] Figure 4 schematically shows a cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. The embodiment corresponds to the embodiment disclosed in relation to Figures 3a-3c, with the difference that the fuel gas supply system further comprises a second fuel gas valve 190 having a fuel gas nozzle relative to the cylinder. The second fuel gas valve 190 is at least partially located in the cylinder cover 112, and the nozzle of the second fuel gas valve has a first nozzle opening configured to inject fuel gas along a second nozzle axis 152. The second nozzle axis 152 is angled with respect to the axial direction. At least a portion of the nozzle of the second fuel gas valve 190 is located in the cylinder cover 112 above a second portion 161 of the cylinder, and the second nozzle axis has an upper part 173 extending into the second portion of the cylinder 161 and a lower part 174 extending into the first portion of the cylinder 160. At bottom dead center, piston 103 is positioned below both the upper 173 and lower 174 of the second nozzle shaft 152. At top dead center, piston 103 is positioned above the entire lower 174 of the second nozzle shaft 152. The second fuel gas valve 190 is configured to initiate fuel gas injection during the compression stroke before piston 103 reaches the lower 174 of the second nozzle shaft 152. As a result, a particularly effective mixture of fuel gas and scavenging is achieved by having a first fuel gas valve 105 positioned above the first portion 160 of the cylinder that directs fuel gas toward the second portion of the cylinder 161, and a second fuel gas valve 190 positioned above the second portion of the cylinder 160 that directs fuel gas toward the first portion of the cylinder 160. In this embodiment, the first nozzle shaft 150 intersects with the second nozzle shaft 152. As a result, the jet from the first fuel gas valve 105 collides with the jet from the second fuel gas valve 190, leading to improved distribution of fuel gas in the cylinder, thereby resulting in improved mixing of fuel gas and scavenging.

[0060] Figure 5 schematically shows the upper end of a cylinder 115 provided with a cylinder cover 112 according to an embodiment of the present invention. A first fuel gas valve 105 is at least partially located within the cylinder cover 112. The first fuel gas valve 105 has a nozzle 195. The nozzle 195 of the first fuel gas valve has a first nozzle opening configured to inject fuel gas along a first nozzle axis 150 that is angled with respect to the axial direction. The cylinder cover 112 has an exhaust valve 104. The nozzle 195 of the first fuel gas valve 105 protrudes into the main combustion chamber, and the first fuel gas valve 105 is configured to begin injecting fuel gas before the exhaust valve 104 closes. The exhaust valve, having a valve plate, is movable along a central axis between a closed position and an open position, and the exhaust valve plate is positioned at a first height in the closed position and a second height in the open position. The exhaust valve 104 is shown in Figure 5 with the valve plate in the open position. The first height is higher than the second height, and the distal end of the nozzle 195 is positioned below the second height, i.e., below the height of the exhaust valve plate when the exhaust valve is open. As a result, fuel gas injection may be initiated earlier without resulting in increased direct gas leakage through the exhaust valve.

[0061] Figure 6 schematically illustrates a fuel gas valve 105 according to an exemplary embodiment of the present invention. The fuel gas valve 105 is at least partially located within the cylinder cover and has a nozzle. The nozzle of the fuel gas valve 105 has a first nozzle opening 195 configured to inject fuel gas along a first nozzle axis 150 which is angled with respect to the axial direction 156. The nozzle of the fuel gas valve 105 further has a second nozzle opening 196 configured to inject fuel gas along a third nozzle axis 199. The third nozzle axis 199 is angled with respect to the axial direction 156. The angle between the third nozzle axis 199 and the axial direction 156 is greater than the angle between the first nozzle axis 150 and the axial direction 156. As a result, the second nozzle opening 196 can be reliably configured to supply fuel gas to the upper part of the combustion chamber, thereby achieving better axial distribution of fuel gas. Since the first nozzle opening 195 can distribute fuel gas to a larger portion of the main combustion chamber than the second nozzle opening 196, the first nozzle opening 195 may be larger than the second nozzle opening 196.

[0062] While several embodiments have been described and demonstrated in detail, the present invention is not limited thereto and may be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it should 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.

[0063] In a device claim that lists several means, some of these means may be embodied by the same item of hardware. The mere fact that certain means are described in different dependent claims or in different embodiments does not imply that combinations of these means cannot be used advantageously.

[0064] When used herein, the term “equipped with / possessed by” is interpreted to specify the presence of the described feature, integer, step, or component, but it should be emphasized that this does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. The invention described in the original claims of this application is listed below. [1] A two-stroke uniflow scavenging crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system, The cylinder has a cylinder wall, the cylinder cover is located at the upper end of the cylinder and has an exhaust valve, the piston is movably positioned within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system has a scavenging inlet located at the bottom of the cylinder, and the fuel gas supply system comprises a first fuel gas valve configured to allow fuel gas to enter a main combustion chamber defined between the piston and the cylinder cover during a compression stroke, via a fuel gas nozzle that enables mixing fuel gas with scavenging from the scavenging inlet and compressing the mixture of scavenging and fuel gas before ignition. A two-stroke uniflow scavenging crosshead internal combustion engine, characterized in that the first fuel gas valve is at least partially located within the cylinder cover, and the nozzle of the first fuel gas valve has a first nozzle opening configured to inject fuel gas along a first nozzle axis, the first nozzle axis being at an angle to the axial direction. [2] The two-stroke uniflow scavenging crosshead internal combustion engine according to [1], wherein the cylinder has a first portion and a second portion separated by a reference plane extending along the central axis, at least a portion of the nozzle of the first fuel gas valve is located in the cylinder cover above the first portion of the cylinder, and the first nozzle shaft has an upper portion extending into the first portion of the cylinder and a lower portion extending into the second portion of the cylinder. [3] The two-stroke uniflow scavenging crosshead internal combustion engine according to [2], wherein the piston at bottom dead center is located below both the upper and lower parts of the first nozzle shaft, the piston at top dead center is located above the entire lower part of the first nozzle shaft, and the first fuel gas valve is configured to initiate fuel gas injection during the preceding compression stroke when the piston is above the entire lower part of the first nozzle shaft. [4] The fuel gas supply system comprises a second fuel gas valve having a fuel gas nozzle relative to the cylinder, the second fuel gas valve being at least partially located in the cylinder cover, the nozzle of the second fuel gas valve having a first nozzle opening configured to inject fuel gas along a second nozzle axis, the second nozzle axis being at an angle with respect to the axial direction, the two-stroke uniflow scavenging crosshead internal combustion engine according to [2] or [3]. [5] The two-stroke uniflow scavenging crosshead internal combustion engine according to [4], wherein at least a portion of the nozzle of the second fuel gas valve is located in a cylinder cover above the second portion of the cylinder, and the second nozzle shaft has an upper portion extending into the second portion of the cylinder and a lower portion extending into the first portion of the cylinder. [6] The two-stroke uniflow scavenging crosshead internal combustion engine according to [5], wherein the piston at bottom dead center is positioned below both the upper and lower parts of the second nozzle shaft, the piston at top dead center is positioned above the entire lower part of the second nozzle shaft, and the second fuel gas valve is configured to initiate fuel gas injection during the preceding compression stroke when the piston is above the entire lower part of the second nozzle shaft. [7] The two-stroke uniflow scavenging crosshead internal combustion engine according to [6], wherein the first nozzle shaft intersects with the second nozzle shaft. [8] The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to [7], wherein the first fuel gas valve is configured to initiate fuel gas injection before closing the exhaust valve. [9] The engine having a stroke of X mm, and the first nozzle opening of the nozzle of the first fuel gas valve having a diameter of Y, where Y is between 1% and 4% of X, is the two-stroke uniflow scavenging crosshead internal combustion engine as described in [8].

[10] A two-stroke uniflow scavenging crosshead internal combustion engine according to [8] or [9], wherein the first fuel gas valve is configured to initiate fuel gas injection 95 degrees, 90 degrees, or 85 degrees before bottom dead center.

[11] The nozzle of the first fuel gas valve protrudes into the main combustion chamber, and the first fuel gas valve is configured to initiate fuel gas injection before the exhaust valve is closed, as described in any one of [1] to

[10] , for a two-stroke uniflow scavenging crosshead internal combustion engine.

[12] The exhaust valve has a valve plate which is movable along a central axis between a closed position and an open position, and the exhaust valve plate is positioned at a first height in the closed position and at a second height in the open position, the first height being higher than the second height, and the distal end of the nozzle being lower than the second height, as described in

[11] .

[13] The exhaust valve has a valve plate which is movable along the exhaust valve axis between a closed position and an open position, the center of the first nozzle opening is located at a first distance from the central axis, and the center of the valve plate of the exhaust valve is located at a second distance from the central axis, the second distance being longer than the first distance, the two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to

[11] .

[14] A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to

[13] , wherein the first fuel gas valve is configured to inject fuel gas for an injection period, the injection period being shorter than the time required to rotate the crank angle by 30 degrees.

[15] A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to

[14] , wherein the first fuel gas valve has a second nozzle opening configured to inject fuel gas along a third nozzle axis, the third nozzle axis being at an angle with respect to the axial direction, and the angle between the third nozzle axis and the axial direction being greater than the angle between the first nozzle axis and the axial direction.

Claims

1. A two-stroke uniflow scavenging crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system, The cylinder has a cylinder wall, the cylinder cover is located at the upper end of the cylinder and has an exhaust valve, the piston is movably positioned within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system has a scavenging inlet located at the bottom of the cylinder, and the fuel gas supply system comprises a first fuel gas valve configured to allow fuel gas to enter a main combustion chamber defined between the piston and the cylinder cover during a compression stroke, via a fuel gas nozzle that enables mixing fuel gas with scavenging from the scavenging inlet and compressing the mixture of scavenging and fuel gas before ignition. A two-stroke uniflow scavenging crosshead internal combustion engine, characterized in that the first fuel gas valve is at least partially located in the cylinder cover, the nozzle of the first fuel gas valve has a first nozzle opening configured to inject fuel gas along a first nozzle axis, the first nozzle axis is angled with respect to the axial direction, the fuel gas supply system is configured to complete the injection of fuel gas before the piston reaches top dead center, and the first fuel gas valve is configured to inject fuel gas to form a fuel gas jet that collides with the cylinder wall, thereby resulting in a homogeneous mixture of fuel gas and scavenging.

2. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 1, wherein the cylinder has a first portion and a second portion separated by a reference plane extending along the central axis, at least a portion of the nozzle of the first fuel gas valve is disposed in the cylinder cover above the first portion of the cylinder, and the first nozzle shaft has an upper portion extending into the first portion of the cylinder and a lower portion extending into the second portion of the cylinder.

3. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 2, wherein the piston at bottom dead center is positioned below both the upper and lower parts of the first nozzle shaft, the piston at top dead center is positioned above the entire lower part of the first nozzle shaft, and the first fuel gas valve is configured to initiate fuel gas injection during the compression stroke prior to when the piston is above the entire lower part of the first nozzle shaft.

4. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 2, wherein the fuel gas supply system comprises a second fuel gas valve having a fuel gas nozzle relative to the cylinder, the second fuel gas valve being at least partially located in the cylinder cover, and the nozzle of the second fuel gas valve having a first nozzle opening configured to inject fuel gas along a second nozzle axis, the second nozzle axis being at an angle with respect to the axial direction.

5. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 4, wherein at least a portion of the nozzle of the second fuel gas valve is located in a cylinder cover above the second portion of the cylinder, and the second nozzle shaft has an upper portion extending over the second portion of the cylinder and a lower portion extending over the first portion of the cylinder.

6. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 5, wherein the piston at bottom dead center is positioned below both the upper and lower parts of the second nozzle shaft, the piston at top dead center is positioned above the entire lower part of the second nozzle shaft, and the second fuel gas valve is configured to initiate fuel gas injection during the preceding compression stroke when the piston is above the entire lower part of the second nozzle shaft.

7. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 6, wherein the first nozzle shaft intersects with the second nozzle shaft.

8. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 7, wherein the first fuel gas valve is configured to initiate fuel gas injection before closing the exhaust valve.

9. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 8, wherein the engine has a stroke of X mm, and the first nozzle opening of the nozzle of the first fuel gas valve has a diameter of Y, where Y is between 1% and 4% of X.

10. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 8, wherein the first fuel gas valve is configured to initiate fuel gas injection before the crankshaft rotates 95 degrees, 90 degrees, or 85 degrees from bottom dead center.

11. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 7, wherein the nozzle of the first fuel gas valve protrudes into the main combustion chamber, and the first fuel gas valve is configured to begin injecting fuel gas before the exhaust valve is closed.

12. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 11, wherein the exhaust valve has a valve plate, the valve plate is movable along a central axis between a closed position and an open position, the exhaust valve plate is positioned at a first height in the closed position and at a second height in the open position, the first height being higher than the second height, and the distal end of the nozzle being lower than the second height.

13. The exhaust valve has a valve plate, the valve plate is movable along the exhaust valve axis between a closed position and an open position, the center of the first nozzle opening is located at a first distance from the central axis, and the center of the valve plate of the exhaust valve is located at a second distance from the central axis, the second distance being longer than the first distance, the two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 7.

14. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 7, wherein the first fuel gas valve is configured to inject fuel gas for an injection period, the injection period being shorter than the time required to rotate the crank angle by 30 degrees.

15. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 7, wherein the first fuel gas valve has a second nozzle opening configured to inject fuel gas along a third nozzle axis, the third nozzle axis is at an angle with respect to the axial direction, and the angle between the third nozzle axis and the axial direction is greater than the angle between the first nozzle axis and the axial direction.

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