CN115707862A - Internal combustion engine - Google Patents

Abstract

A two-stroke uniflow-scavenged crosshead internal combustion engine is disclosed, 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 fuel gas supply system includes a first fuel gas valve for the cylinder configured to admit fuel gas into a main combustion chamber defined between the piston and the cylinder head via a fuel gas nozzle during a compression stroke. A first fuel gas valve is at least partially disposed in the cylinder head, a nozzle of the first fuel gas valve having a first nozzle opening configured to inject fuel gas along a first nozzle axis, and wherein the first nozzle axis is angled relative to the axial direction.

Description

Internal combustion engine

Technical Field

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

Background

Two-stroke internal combustion engines are used as propulsion engines in vessels such as container ships, bulk carriers and tankers. It has become increasingly important to reduce the undesirable emissions from internal combustion engines.

An effective way to reduce the amount of undesirable exhaust gas is to replace fuel oil, such as Heavy Fuel Oil (HFO), with fuel gas. The fuel gas may be injected into the cylinder at the end of the compression stroke, where it may be immediately ignited by the high temperature reached by the gas in the cylinder when it is compressed or by igniting a pilot fuel. However, injecting fuel gas into the cylinder at the end of the compression stroke requires a high pressure gas compressor to compress the fuel gas prior to injection to overcome the higher pressure in the cylinder.

However, the high pressure gas compressor is expensive and complicated to manufacture and maintain. One way to avoid the need for a high pressure compressor is to have a fuel gas valve configured to inject fuel gas at the beginning of the compression stroke where the pressure in the cylinder is significantly lower.

DK 176118B discloses an engine where gas is injected into the scavenging inlet or directly into the cylinder through the cylinder wall.

WO 2013007863 discloses another example of such an engine in which gas is injected directly into the cylinder through the cylinder wall.

However, it may be difficult to achieve rapid and efficient mixing between the scavenging gas and the fuel gas in the cylinder.

The heterogeneous mixture of fuel gas and scavenging gas may result in poor combustion of the fuel gas or even pre-ignition leading to knock.

Thus, improving the mixing of the fuel gas with the scavenging gas in the cylinder remains a problem.

Disclosure of Invention

According to a first aspect, the invention relates to a two-stroke single-flow scavenged crosshead internal combustion engine comprising at least one cylinder having a cylinder wall, a cylinder head arranged at the top of the cylinder and having an exhaust valve, a cylinder head having a central axis movably arranged within the cylinder between a bottom dead centre and a top dead centre, a piston having a scavenging inlet arranged at the bottom of the cylinder, a fuel gas supply system connectable to a fuel gas tank, and a scavenging system comprising a first fuel gas valve for the cylinder configured to admit fuel gas into a main combustion chamber defined between the piston and the cylinder head via a fuel gas nozzle during a compression stroke so that the fuel gas can be mixed with scavenging gas from the scavenging inlet and to allow a mixture of the scavenging gas and the fuel gas to be compressed before ignition, wherein the first fuel gas valve is arranged at least partially in the cylinder head, the nozzle of the first fuel gas valve having a first nozzle opening configured to inject the fuel gas in an angular direction along the first nozzle axis, and wherein the first nozzle axis is angled relative to the first axial direction.

Thus, by arranging the fuel gas valves in the cylinder head and angling the fuel gas nozzles with respect to the axial direction, the generated fuel gas jets may impinge a large portion of the cylinder wall, thereby creating a homogeneous mixture of fuel gas and scavenging gas.

The internal combustion engine is preferably a large low speed turbocharged two-stroke uniflow scavenged crosshead internal combustion engine for propelling a vessel with a power of at least 400kW per cylinder. The internal combustion engine may include a turbocharger driven by exhaust gas generated by the internal combustion engine and configured to compress the scavenging gas. The internal combustion engine may be a dual fuel engine having an Otto Cycle (Otto Cycle) mode when operating with fuel gas and a Diesel Cycle (Diesel Cycle) mode when operating with an alternative fuel, such as heavy fuel oil or marine Diesel. Such dual fuel engines have their own dedicated fuel supply system for injecting alternative fuel, and such fuel supply system may also be used to inject a pilot fuel when operating in an otto cycle mode for igniting a mixture of fuel gas and scavenging.

The internal combustion engine may include a dedicated ignition system, such as a pilot fuel system, which is capable of injecting a small amount of pilot fuel (e.g., heavy fuel oil or marine diesel) that is accurately measured so that the amount is only capable of igniting a mixture of fuel gas and scavenging gas, such that only the necessary amount of pilot fuel is used. Such a pilot fuel system is much smaller in size and more suitable for injecting precise quantities of pilot fuel than dedicated fuel supply systems for alternative fuels that are not suitable for such purposes due to the large size of the components.

The pilot fuel may be injected into a pre-chamber that is fluidly connected to a combustion chamber of the internal combustion engine. Alternatively, the mixture of fuel gas and scavenging gas may be ignited by means including a spark plug or laser igniter. Each cylinder may be provided with one or more scavenge inlets at the bottom of the cylinder and a drain outlet at the top of the cylinder.

The fuel gas supply system is preferably configured to inject fuel gas via one or more fuel gas valves under sonic conditions (i.e. at a velocity equal to that of sound, i.e. at a uniform velocity). Sonic conditions may be achieved when the pressure drop ratio across the nozzle throat (minimum cross-sectional area) is greater than about two.

The central axis extends in an axial direction. The first fuel gas valve as a whole may be arranged in the cylinder head. Alternatively, only a part of the first fuel gas valve may be disposed in the cylinder head, for example, the nozzle may be disposed in the cylinder head, and the remaining fuel gas valve portion may be disposed outside the cylinder head. However, a portion of the fuel gas nozzle may also be disposed outside the cylinder head, e.g., the most distal end of the fuel gas nozzle may protrude into the primary combustion chamber, as further explained below. The nozzle of the first fuel gas valve may have a distal portion extending along a first nozzle axis, e.g. the distal portion may have a tubular shape, wherein the first nozzle axis is arranged in the center.

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

Examples of fuel gases are natural gas, methane, ethane, liquefied petroleum gas and ammonia.

In some embodiments, the cylinder has a first half and a second half divided by a reference plane extending along the central axis, wherein at least a portion of the nozzle of the first fuel gas valve is disposed in the cylinder head above the first half of the cylinder, and the first nozzle axis has an upper portion extending in the first half of the cylinder and a lower portion extending in the second half of the cylinder.

Thus, by arranging the first fuel gas valve above the first half of the cylinder and configured to inject fuel gas towards the second half of the cylinder, the generated fuel gas jet may impinge the cylinder wall with a high radial momentum, which may help to distribute the fuel gas throughout the main combustion chamber.

The first and second halves of the cylinder may be of equal size. The first nozzle axis may have a radial component and an axial component, wherein the reference plane is arranged perpendicular to the radial component of the first nozzle axis. The first nozzle axis may optionally also have a tangential component.

In some embodiments, the piston is disposed below both the upper and lower portions of the first nozzle axis at a bottom dead center, the piston is disposed above the entire lower portion of the first nozzle axis at a top dead center, and wherein the first fuel gas valve is configured to begin injecting fuel gas during the compression stroke before the piston is above the entire lower portion of the first nozzle axis.

Thus, the generated fuel gas jet may impinge the cylinder wall before the movement of the piston prevents access to the portion of the cylinder wall during the compression stroke.

The first fuel gas valve may be configured to begin injecting fuel gas before the piston reaches a lower portion of the first nozzle axis during a compression stroke. The first fuel gas valve may inject fuel gas during an injection period, wherein the injection period ends before the piston is located over an entire lower portion of the first nozzle axis.

In some embodiments, the fuel gas supply system includes a second fuel gas valve for the cylinder having a fuel gas nozzle, the second fuel gas valve being at least partially disposed in the cylinder head, the nozzle of the second fuel gas valve having a first nozzle opening configured to inject fuel gas along a second nozzle axis, and wherein the second nozzle axis is angled relative to the axial direction.

The second fuel gas valve may correspond to the first fuel gas valve.

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

Thus, by arranging the first fuel gas valve above the first half of the cylinder to direct the fuel gas towards the second half of the cylinder and the second fuel gas valve above the second half of the cylinder to direct the fuel gas towards the first half of the cylinder, the fuel gas and the scavenging gas are mixed particularly efficiently.

In some embodiments, the piston is disposed below both the upper and lower portions of the second nozzle axis at a bottom dead center, the piston is disposed above the entire lower portion of the second nozzle axis at a top dead center, and wherein the second fuel gas valve is configured to begin injecting fuel gas during the compression stroke before the piston is located above the entire lower portion of the second nozzle axis.

The second fuel gas valve may be configured to begin injecting fuel gas before the piston reaches a lower portion of the second nozzle axis during a compression stroke. The second fuel gas valve may inject fuel gas during an injection period, wherein the injection period ends before the piston is located over an entire lower portion of the second nozzle axis.

In some embodiments, the first nozzle axis intersects the second nozzle axis.

Therefore, the jet from the first fuel gas valve collides with the jet from the second fuel gas valve, thereby improving the mixing of the fuel gas with the scavenging gas.

In some embodiments, the first fuel gas valve is configured to begin injecting fuel gas before the exhaust valve closes.

The applicant has found that if the fuel gas leaving the fuel gas nozzle has a sufficiently high momentum, the injection of fuel gas can be started before the exhaust valve closes, without causing a substantial direct leakage of fuel gas through the exhaust valve. By ensuring that the fuel gas is injected at sonic conditions and by using a nozzle with a large throat, a high momentum of the fuel gas can be achieved.

In some embodiments, the stroke of the engine is X mm and the diameter of the first nozzle opening of the nozzle of the first fuel gas valve is Y, and wherein Y is between 1% and 4% of X.

Therefore, by using a nozzle having a diameter of between 1% and 4% of the hole size (being the major diameter), it is possible to ensure injection of the fuel gas with high momentum.

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

Thus, by starting the injection earlier, more time is provided to allow the fuel gas to mix with the scavenging gas.

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

It can thus be ensured that no or only a small amount of fuel gas is allowed to leak out directly from the open vent valve.

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

Therefore, the injection of the fuel gas can be started earlier without causing an increase in direct gas leakage through the exhaust valve.

In some embodiments, the exhaust valve has a valve plate, wherein the valve plate of the exhaust valve is movable along the central axis between a closed position and an open position, wherein the exhaust valve plate is arranged 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 wherein the distal end of the nozzle is arranged below the second height, i.e. below the height of the exhaust valve plate when the exhaust valve is open.

In some embodiments, the exhaust valve has a valve plate, wherein the valve plate is movable along an exhaust valve axis between a closed position and an open position, wherein a center of the first nozzle opening is disposed a first distance from the central axis, wherein a center of the valve plate of the exhaust valve is disposed a second distance from the central axis, and wherein the second distance is greater than the first distance.

Thus, by placing the exhaust valve eccentrically, the first fuel gas valve can obtain a more centered position in the cylinder head. This may also allow the ignition system to be in a more central position, e.g. the prechamber or group of prechambers may be arranged at the position of the central exhaust.

The exhaust valve axis may be parallel to the central axis, whereby the distance of the centre of the valve plate to the central axis corresponds to the distance between the central axis and the exhaust valve axis. The cylinder head may have a plurality of eccentric exhaust valves, such as at least two, at least three, or at least four eccentric exhaust valves. The first distance may be less than 25% of the cylinder bore.

In some embodiments, the first fuel gas valve is configured to inject fuel gas during an injection period, and wherein the injection period is shorter than a time taken for a crank angle rotation of 30 degrees.

In some embodiments, the first fuel gas valve has a second nozzle opening configured to inject fuel gas along a third nozzle axis, and wherein the third nozzle axis is angled relative to the axial direction, and wherein an angle between the third nozzle axis and the axial direction is greater than an angle between the first nozzle axis and the axial direction.

Thus, a better axial distribution of the fuel gas can be achieved, since the second nozzle opening can ensure that the fuel gas is supplied to the upper part of the main combustion chamber.

The different aspects of the invention, including the two-stroke uniflow-scavenged crosshead internal combustion engine as described above and below, each yielding one or more of the benefits and advantages described in connection with at least one of the above described aspects and each having one or more preferred embodiments corresponding to the preferred embodiments described in connection with at least one of the above described aspects and/or disclosed in the dependent claims, may be implemented in different ways. Furthermore, it should be understood that embodiments described in connection with one of the aspects described herein may be equally applicable to the other aspects.

Drawings

The above and/or additional objects, features and advantages of the present invention will be further elucidated by the following illustrative and non-limitative detailed description of an embodiment of the present invention with reference to the accompanying drawings, in which:

fig. 1 schematically shows a cross section of a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention.

Fig. 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.

Figures 3a to 3c schematically show cross-sections of a two stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention.

Figure 4 schematically shows a cross section of a two stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the invention.

Fig. 5 schematically shows the top of a cylinder provided with a cylinder head according to an embodiment of the invention.

Fig. 6 schematically illustrates a fuel gas valve according to an embodiment of the invention.

Detailed Description

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

Fig. 1 schematically shows a cross section of a two-stroke uniflow-scavenging internal combustion engine 100 for propelling a marine vessel according to an embodiment of the 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 a single cylinder is shown in cross section). Each cylinder 101 comprises a scavenging inlet 102 arranged in a lower section of the cylinder for providing scavenging air, a piston 103, a cylinder head 112 arranged on top of the cylinder, an exhaust valve 104 arranged in the cylinder head 112, and one or more fuel gas valves 105 (only schematically illustrated). The scavenge inlet 102 is fluidly connected to a scavenge 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 arranged in the cylinder between a bottom dead center and a top dead center along a center axis 113. The central axis 113 extends in the axial direction. The fuel gas valve 105 is configured to admit fuel gas into a main combustion chamber defined between the piston 103 and the cylinder head 112 via a fuel gas nozzle (not shown) during a compression stroke, so that the fuel gas can be mixed with scavenging gas. The fuel gas valve 105 is at least partially disposed in the cylinder head 112, and a 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 angled with respect to the axial direction. Thus, by arranging the fuel gas valve 105 in the cylinder head 120 and angling the fuel gas nozzles with respect to the axial direction, the resulting fuel gas jet may impinge a large portion of the cylinder wall, thereby creating a homogeneous mixture of fuel gas and scavenging gas.

The internal combustion engine 100 includes a dedicated ignition system 116 for igniting the mixture of fuel gas and scavenging gas at the end of the compression stroke. As an example, the dedicated ignition system may be a pilot fuel system capable of injecting a small amount of pilot fuel (e.g., heavy fuel oil or marine diesel), which is accurately measured so that the amount is only capable of igniting a mixture of fuel gas and scavenging gas, so that only the necessary amount of pilot fuel is used. Such pilot fuel systems are much smaller in size and more suitable for injecting precise quantities of pilot fuel than dedicated fuel supply systems for alternative fuels, which are not suitable for such purposes due to the large size of the components. The pilot fuel may be injected into a pre-chamber that is fluidly connected to a combustion chamber of the internal combustion engine. Alternatively, the pilot fuel may be injected into a set of pre-combustion chambers fluidly connected to the combustion chamber of the internal combustion engine. The fuel gas valve 105 may be configured to start injecting the fuel gas before 95 degrees from bottom dead center, before 90 degrees from bottom dead center, or before 85 degrees from bottom dead center. The first fuel gas valve may be configured to start injecting the fuel gas after 40 degrees, 50 degrees or 60 degrees from bottom dead center.

The scavenging system 111 includes a scavenging receiver 110 and an air cooler 106. The exhaust valve is arranged centrally in the cylinder head and the timing of the exhaust valve may be variable, so that the closing and/or opening of the exhaust valve may be optimized, for example to control the compression ratio and/or the temperature in the cylinder.

Fig. 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 invention. The fuel gas valve 200 is shown in a horizontal position in the figure, however, the fuel gas valve may be arranged at any angle relative to the axial direction. The fuel gas valve 200 includes 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 is shown with a single nozzle opening, however, the fuel gas valve may have multiple nozzle openings. The valve shaft 201 and the valve plate 202 are movable between a closed position, in which fuel gas is prevented from flowing through the fuel gas valve 200, and an open position, in which fuel gas is allowed to flow through the fuel gas valve 200. The valve shaft 201 and valve plate 202 are shown in the closed position in fig. 2. The valve shaft 201 and the valve plate 202 may be movable between a closed position and an open position by means of an actuator (not shown) controlled by a control unit (not shown). The first nozzle opening 206 is configured to inject fuel gas along a first nozzle axis 250.

Fig. 3a to 3c schematically show cross-sections of a two-stroke uniflow-scavenged crosshead internal combustion engine according to an embodiment of the invention, where fig. 3a shows the engine with the piston in bottom dead centre, fig. 3b shows the engine with the piston in the middle of the compression stroke, and fig. 3c shows the engine with the piston in top dead centre. The two-stroke single-flow scavenging crosshead internal combustion engine comprises at least one cylinder 115, a cylinder head 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, a cylinder head 112 is arranged at the top of the cylinder 115 and has an exhaust valve 104, and the piston 103 is movably arranged in the cylinder 115 along a centre axis 113 between a bottom dead centre and a top dead centre. The central axis 113 extends in the axial direction. The scavenging system has a scavenging inlet 102 arranged at the bottom of the cylinder 115, the fuel gas supply system comprising a first fuel gas valve 105 for the cylinder configured to admit fuel gas via a fuel gas nozzle into a main combustion chamber defined between the piston 103 and the cylinder head 112 during a compression stroke, so that the fuel gas can mix with scavenging gas from the scavenging inlet 102 and allow the mixture of scavenging gas and fuel gas to be compressed before ignition. The first fuel gas valve 105 is at least partially disposed in the cylinder head 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 angled 157 relative to the axial direction and the central axis. In this embodiment, the angle is about 22 degrees. However, in other embodiments, the angle between the first nozzle axis and the axial direction is between 5 degrees and 50 degrees, 10 degrees and 40 degrees, or 15 degrees and 30 degrees. First nozzle axis 150 has a radial component 155 and an axial component 156. The cylinder 115 has a first half 160 and a second half 161 divided by a reference plane 151 extending along the central axis 113. The reference plane 151 is arranged perpendicular to a radial component 155 of the first nozzle axis 150, i.e. the reference plane 151 is also perpendicular to the plane of the drawing. The nozzle of the first fuel gas valve 105 is arranged in the cylinder head 112 above the first half 160 of the cylinder, and the first nozzle axis 150 has an upper part 170 extending in the first half of the cylinder (in the cylinder interior) and a lower part 171 extending in the second half of the cylinder (in the cylinder interior). The piston 103 is arranged below the upper part 170 and the lower part 171 of the first nozzle axis 150 at a bottom dead center (see fig. 3 a), and the piston 103 is arranged above the entire lower part 171 of the first nozzle axis 150 at a top dead center (see fig. 3 c). The first fuel gas valve 105 is configured to start injecting fuel gas before the piston 103 reaches the lower portion 171 of the first nozzle axis (i.e. before the piston 103 reaches the position shown in fig. 3 b) during the compression stroke. Thus, by arranging the first fuel gas valve above the first half of the cylinder and configured to inject fuel gas towards the second half of the cylinder, the resulting jet of fuel gas may impinge the cylinder wall with a high radial momentum, which helps to distribute the fuel gas throughout the main combustion chamber.

Figure 4 schematically shows a cross section of a two stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the invention. This embodiment corresponds to the embodiment disclosed in relation to fig. 3a to 3c, with the difference that the fuel gas supply system further comprises a second fuel gas valve 190 with a fuel gas injection nozzle for the cylinder. A second fuel gas valve 190 is at least partially disposed in the cylinder head 112, a nozzle of the second fuel gas valve having a first nozzle opening configured to inject fuel gas along a second nozzle axis 152. The second nozzle axis 152 is angled relative to the axial direction. At least a portion of the nozzle of the second fuel gas valve 190 is disposed in the cylinder head 112 above the second half 161 of the cylinder, and the second nozzle axis has an upper portion 173 extending in the second half 161 of the cylinder and a lower portion 174 extending in the first half 160 of the cylinder. The piston 103 is arranged below both the upper part 173 and the lower part 174 of the second nozzle axis 152 at a lower stop. The piston 103 is arranged above the entire lower part 174 of the second nozzle axis 152 at top dead center. The second fuel gas valve 190 is configured to begin injecting fuel gas before the piston 103 reaches the lower portion 174 of the second nozzle axis 152 during the compression stroke. Therefore, the fuel gas is guided toward the second half 161 of the cylinder by arranging the first fuel gas valve 105 above the first half 160 of the cylinder and the fuel gas is guided toward the first half 160 of the cylinder by arranging the second fuel gas valve 190 above the second half 161 of the cylinder, so that the fuel gas and the scavenging gas are mixed particularly efficiently. In this embodiment, the first nozzle axis 150 intersects the second nozzle axis 152. Therefore, the jet from the first fuel gas valve 105 collides with the jet from the second fuel gas valve 190, so that the distribution of the fuel gas in the cylinder is improved, thereby improving the mixing of the fuel gas with the scavenging gas.

Fig. 5 schematically shows the top of a cylinder 115 provided with a cylinder head 112 according to an embodiment of the invention. The first fuel gas valve 105 is at least partially disposed in the cylinder head 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 relative to the axial direction. The cylinder head 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 start injecting fuel gas before the exhaust valve 104 is closed. The exhaust valve has a valve plate movable along a central axis between a closed position and an open position, wherein the exhaust valve plate is disposed at a first elevation in the closed position and at a second elevation in the open position. The exhaust valve 104 is shown in fig. 5 with the valve plate in an open position. The first height is higher than the second height and the distal tip of the nozzle 195 is disposed below the second height, i.e., below the height of the exhaust valve plate when the exhaust valve is open. Therefore, the injection of the fuel gas can be started earlier without causing an increase in direct gas leakage through the exhaust valve.

Fig. 6 schematically illustrates a fuel gas valve 105 according to an embodiment of the present invention. The fuel gas valve 105 is at least partially disposed in the cylinder head 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 that is angled relative 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 third nozzle axis 199 and axial direction 156 is greater than the angle between first nozzle axis 150 and axial direction 156. Accordingly, since the second nozzle openings 196 can ensure that the fuel gas is supplied to the upper portion of the combustion chamber, better axial distribution of the fuel gas can be achieved. The first nozzle opening 195 may be larger than the second nozzle opening 196 because the first nozzle opening 195 may distribute the fuel gas to a larger portion of the main combustion chamber than the second nozzle opening 196.

Although some embodiments have been described and shown in detail, the invention is not limited thereto but may be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it is to 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.

In the 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.

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

Claims (15)

1. A two-stroke, single-flow, scavenged crosshead internal combustion engine comprising at least one cylinder having a cylinder wall, a cylinder head arranged at the top of the cylinder and having an exhaust valve, a fuel gas supply system connectable to a fuel gas tank, 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 within the cylinder along a central axis between a bottom dead center and a top dead center, the scavenging system having a scavenging inlet arranged at the bottom of the cylinder, the fuel gas supply system comprising a first fuel gas valve for the cylinder configured to admit fuel gas via a fuel gas nozzle into a main combustion chamber defined between the piston and the cylinder head during a compression stroke, so that fuel gas can mix with scavenging gas from the scavenging inlet and to allow a mixture of scavenging gas and fuel gas to be compressed before ignition,it is characterized in that In that,the first fuel gas valve is at least partially disposed in the cylinder head, a nozzle of the first fuel gas valve having a first nozzle opening configured to inject fuel gas along a first nozzle axisAnd wherein the first nozzle axis is angled relative to the axial direction.

2. A two-stroke, single-flow, scavenged, crosshead internal combustion engine as in claim 1, wherein the cylinder has a first half and a second half divided by a reference plane extending along the central axis, wherein at least a portion of the nozzle of the first fuel gas valve is disposed in the cylinder head above the first half of the cylinder, the first nozzle axis having an upper portion extending in the first half of the cylinder and a lower portion extending in the second half of the cylinder.

3. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to claim 2, wherein the piston is disposed below both the upper and lower portions of the first nozzle axis at a bottom dead center, the piston is disposed above the entire lower portion of the first nozzle axis at a top dead center, and wherein the first fuel gas valve is configured to begin injecting fuel gas before the piston is above the entire lower portion of the first nozzle axis during a compression stroke.

4. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to claim 2 or 3, wherein the fuel gas supply system includes a second fuel gas valve for the cylinder having a fuel gas nozzle at least partially disposed in the cylinder head, the nozzle of the second fuel gas valve having a first nozzle opening configured to inject fuel gas along a second nozzle axis, and wherein the second nozzle axis is angled relative to the axial direction.

5. A two-stroke, single-flow, scavenged, crosshead internal combustion engine as defined in claim 4 wherein at least a portion of the nozzle of the second fuel gas valve is disposed in the cylinder head above the second half of the cylinder, the second nozzle axis having an upper portion extending in the second half of the cylinder and a lower portion extending in the first half of the cylinder.

6. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to claim 5, wherein the piston is disposed below both the upper and lower portions of the second nozzle axis at a bottom dead center, the piston is disposed above the entire lower portion of the second nozzle axis at a top dead center, and wherein the second fuel gas valve is configured to begin injecting fuel gas before the piston is above the entire lower portion of the second nozzle axis during a compression stroke.

7. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to claim 6, wherein the first nozzle axis intersects the second nozzle axis.

8. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to any one of claims 1 to 7, wherein the first fuel gas valve is configured to commence injection of fuel gas before the exhaust valve closes.

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

10. A two-stroke uniflow-scavenged crosshead internal combustion engine according to claim 8 or 9, wherein the first fuel gas valve is configured to start injecting fuel gas before 95 degrees from bottom dead centre, before 90 degrees or before 85 degrees.

11. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to any one of claims 1 to 10, wherein the nozzle of the first fuel gas valve protrudes into the main combustion chamber, and wherein the first fuel gas valve is configured to begin injecting fuel gas before the exhaust valve closes.

12. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to claim 11, wherein the exhaust valve has a valve plate, wherein the valve plate is movable along the central axis between a closed position and an open position, wherein the exhaust valve plate is disposed 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 wherein the distal end of the nozzle is disposed below the second height.

13. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to any one of claims 1 to 11, wherein the exhaust valve has a valve plate, wherein the valve plate is movable along an exhaust valve axis between a closed position and an open position, wherein a center of the first nozzle opening is disposed a first distance from the central axis, a center of the valve plate of the exhaust valve is disposed a second distance from the central axis, and wherein the second distance is greater than the first distance.

14. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to any one of claims 1 to 13, wherein the first fuel gas valve is configured to inject fuel gas during an injection period, and wherein the injection period is shorter than the time it takes for a crank angle rotation of 30 degrees.

15. A two-stroke, single-flow, scavenged, crosshead internal combustion engine according to any one of claims 1 to 14, wherein the first fuel gas valve has a second nozzle opening configured to inject fuel gas along a third nozzle axis, and wherein the third nozzle axis is angled relative to the axial direction, and wherein 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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