DK180809B1

DK180809B1 - Internal combustion engine

Info

Publication number: DK180809B1
Application number: DKPA202070823A
Authority: DK
Inventors: Hvidtfeldt Rasmussen Niels
Original assignee: Man Energy Solutions Filial Af Man Energy Solutions Se Tyskland
Priority date: 2020-12-09
Filing date: 2020-12-09
Publication date: 2022-04-07
Also published as: JP7159430B2; KR102611647B1; KR20220081922A; CN114622986A; DK202070823A1; JP2022091731A

Abstract

Disclosed is a two-stroke uniflow scavenged 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 scavenge air system, the cylinder having a cylinder wall, the cylinder cover being arranged on top of the cylinder and having an exhaust valve. The fuel gas supply system comprising for the cylinder a fuel gas valve arranged at least partly in the cylinder wall. The fuel gas valve comprising a valve shaft extending along a valve axis, a valve plate, and a valve seat, the valve shaft and the valve plate being movable along the valve axis between an open position and a closed position. The fuel gas valve is configured so that the valve shaft and the valve plate moves in an upstream direction when moving from the closed position to the open position.

Description

DK 180809 B1 1 Title Internal combustion engine Field The present invention relates to a two-stroke internal combustion engine and a fuel gas valve.

Background Two-stroke internal combustion engines are used as propulsion engines in vessels like container ships, bulk carriers, and tankers. Reduction of unwanted exhaust gases from the internal combustion engines has — become increasingly important.

An effective way to reduce the amount of unwanted exhaust gasses is to switch from fuel oil e.g. Heavy Fuel Oil (HFO) to fuel gas. Fuel gas may be injected into the cylinders at the end of the compression stroke where it may be immediately ignited by either the high temperatures which the gases in the cylinders achieve when compressed or by the ignition of a pilot fuel. However, injecting fuel gas into the cylinders at the end of the compression stroke requires high pressure gas compressors for compressing the fuel gas prior to injection to overcome the high pressure in the cylinders.

The high pressure gas compressors are however expensive and complex to manufacture and maintain. One way to avoid the need of high pressure compressors is to have fuel gas valves configured to inject the fuel gas in the beginning of the compression stroke where the pressure in the cylinders is significantly lower.

EP3015679 discloses such a fuel gas valve. The fuel gas valve comprises a valve shaft, a valve plate, and a valve seat, the valve shaft and the valve plate being movable between an open position and a closed position, where the valve plate, in the open position, extends into a gas fuel nozzle connected to the fuel gas valve.

Low pressure two-stroke uniflow scavenged internal combustion engine however suffers from problems with gas slip. This is problematic since the commonly used fuel gases are potent greenhouse gases. As an example,

DK 180809 B1 2 Methane is potentially 84 times more potent as a greenhouse gas than CO2. Thus, even a small gas slip will over the lifetime of an engine result in a significant environmental effect especially if the gas slip is recurring for each engine cycle. Controlling the timing of the exhaust valve and the fuel gas valves may limit the amount of gas slip, but only to a certain degree. Thus, it remains a problem to reduce gas slip further.

Summary — According to a first aspect, the invention relates to a two-stroke uniflow scavenged 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 scavenge air system, the cylinder having a cylinder wall, the cylinder cover being arranged on top of the cylinder and having an exhaust valve, the piston being movably arranged within the cylinder along a central axis between bottom dead center and top dead center, the scavenge air system having a scavenge air inlet arranged at the bottom of the cylinder, the fuel gas supply system comprising for the cylinder a fuel gas valve arranged at least partly in the cylinder wall and configured to admit fuel gas into the cylinder during the compression stroke via a fuel gas nozzle enabling the fuel gas to mix with scavenge air from the scavenge air inlet and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited, the fuel gas valve comprising a valve shaft extending along a valve axis, a valve plate, and a valve seat, the valve shaft and the valve plate being movable along the valve axis between an open position and a closed position, wherein the fuel gas valve is arranged at least partly in the cylinder wall at a height below the piston when the piston is at top dead center, and the fuel gas valve is configured so that the valve shaft and the valve plate moves in an upstream direction when moving from the closed position to the — open position.

DK 180809 B1 3 After the fuel gas valve has closed and the piston has moved past the fuel gas nozzle, a residual volume of fuel gas is captured in the fuel gas nozzle. A part of this residual volume will flow / diffuse into the scavenging space below the piston, where it will mix with scavenging air. In the next engine cycle, when the piston moves below the scavenging air inlets, the mixture will flow into the cylinder and a part of the mixture will be directed directly out the exhaust valve in the beginning of the scavenging process resulting in a gas slip.

Consequently, by inverting the lift direction of the fuel gas valve, the internal volume of the fuel gas nozzle may be reduced as it no longer needs to accommodate the valve plate when the valve shaft and the valve plate is in the open position. Thus, the residual volume of fuel gas left in the fuel gas nozzle when the valve closes may also be reduced which will result in a reduction in the amount of gas slip. The reduced gas slip will further — result in a corresponding increase in efficiency.

The internal combustion engine is preferably a large low-speed turbocharged two-stroke crosshead internal combustion engine with uniflow scavenging for propelling a marine vessel having a power of at least 400 kW per cylinder. The internal combustion engine may comprise a turbocharger driven by the exhaust gases generated by the internal combustion engine and configured to compress the scavenge air. The internal combustion engine may be a dual-fuel engine having a Otto Cycle mode when running on fuel gas and a Diesel Cycle mode when running on an alternative fuel e.g. heavy fuel oil or marine diesel oil. Such dual-fuel engine has its own dedicated fuel supply system for injecting the alternative fuel and this fuel supply system may also be used for injection of a pilot fuel when operating in the Otto Cycle mode for igniting the mixture of fuel gas and scavenge air.

The internal combustion engine may comprise a dedicated ignition system such as a pilot fuel system being capable of injecting a small amount of pilot fuel, e.g. heavy fuel oil or marine diesel oil, accurately measured out so the amount just is able to ignite the mixture of fuel gas and

DK 180809 B1 4 scavenge air such that only the necessary amount of pilot fuel is used. Such a pilot fuel system would in size be much smaller and more suitable for injecting a precisely amount of pilot fuel compared to the dedicated fuel supply system for the alternative fuel, which due to the large size of the components is not suitable for this purpose.

The pilot fuel may be injected in a pre-chamber being fluidly connected to the combustion chamber of the internal combustion engine. Alternatively, the mixture of fuel gas and scavenge air may by ignited by means comprising a spark plug or a laser igniter. Each cylinder may be — provided with one or more scavenge air inlets in the bottom of the cylinder and an exhaust outlet in the top of the cylinder.

The valve shaft and the valve plate may move in an upstream direction, when moving from the closed position to the open position, by moving along the valve axis away from the center of the cylinder.

Correspondingly, the valve shaft and the valve plate may move in an downstream direction, when moving from the open position to the closed position, by moving along the valve axis towards the center of the cylinder. The valve axis may correspond to the radial direction so that the valve shaft and the valve plate may move directly away from the center of the cylinder when moving from the closed position to the open position. However, the valve axis may also be angled relative to the radial direction.

The valve plate may have a first side and a second side, the second side being opposite to the first side, the valve shaft extending from the first side and a part of the second side is abutting the valve seat when the valve is in the closed position.

In some embodiments the fuel gas valve is configured to inject a fuel gas into the cylinder during the compression stroke within O degrees to 160 degrees from bottom dead center, within O degrees to 130 degrees from bottom dead center or within O degrees to 90 degrees from bottom dead center.

DK 180809 B1 Examples of fuel gases are natural gas, methane, ethane, Liquefied Petroleum Gas, and Ammonia.

In some embodiments the fuel gas nozzle is an integral part of the fuel gas valve.

5 Consequently, by incorporating the fuel gas nozzle in the fuel gas valve, the number of engine parts is reduced making the engine simpler.

In some embodiments the fuel gas valve comprises a valve housing, the valve housing comprising a first part and a second part, the fuel gas nozzle and the valve seat being formed in the second part of the valve — housing, and the first part of the valve housing and the second part of the valve housing is connected upstream of the valves seat.

Consequently, it may become easier to detect a gas leakage from the connection between the first part and the second part of the valve housing as a gas leakage from the connection will result in a pressure drop up stream of the fuel gas valve when the fuel gas valve is closed, which may be detected by a sensor as explained in the following.

In some embodiments the fuel gas supply system further comprises a safety valve arranged upstream of the fuel gas valve, the fuel gas valve being fluidly connectable to the fuel gas tank via the safety valve.

In some embodiments the safety valve is configured to open before the fuel gas valve is configured to open and to close after the fuel gas valve is configured to close thereby creating a limited period of time where fuel gas is allowed to flow through the safety valve to the fuel gas valve.

In some embodiments a first sensor is arranged in the volume between the safety valve and the fuel gas valve, the first sensor being configured to detect directly or indirectly a pressure change in the volume between the safety valve and the fuel gas valves indicative of a malfunctioning fuel gas valve.

Consequently, it becomes possible in a reliable manner to detect different types of fuel gas valve malfunctions.

DK 180809 B1 6 The first sensor may be a pressure sensor configured to directly detect the pressure change.

Alternatively, the first sensor may be another sensor configured to indirectly detect the pressure change, e.g. a temperature sensor.

A second sensor may further be arranged in the volume between the safety valve and the fuel gas valve e.g. the first sensor may be a pressure sensor and the second sensor may be a temperature sensor.

The internal combustion engine may further comprise a control unit operationally connected to the first sensor (and possibly also the second sensor). The control unit may be configured to monitor sensor signal received from the first — sensor and issue an alarm if a malfunctioning fuel gas valve is detected e.g. if a pressure drop in the volume between the safety valve and the first group of fuel gas valves is detected indicative of either a damaged valve plate or valve seat, or a stuck valve shaft.

The control unit may be configured to take an action responsive to an alarm e.g. the control unit may secure that the — safety valve of the malfunctioning fuel gas valve is permanently closed and / or initiate a blow operation to blow out gas from the fuel gas supply system and / or control the engine to switch from a gas mode to an alternative mode e.g. a Diesel mode.

In some embodiments the safety valve has a valve housing with aninlet and an outlet, the fuel gas valve has a valve housing with an inlet and an outlet, and wherein the valve housing of the safety valve is directly connected to the valve housing of the fuel gas valve so that the outlet of the safety valve is directly connected to the inlet of the first fuel gas valve.

Consequently, the volume of gas between the safety valve and the fuel gas valve may be small.

This may lower the amount of fuel gas that may be released uncontrollable into the cylinder in the event of a malfunctioning fuel gas valve.

Having a small volume of fuel gas captured between the fuel gas valve and the safety valve may further make it easier to detect a leaking fuel gas valve as the resulting pressure drop will be larger.

In some embodiments the safety valve comprises a valve shaft extending along a valve axis, a valve plate, and a valve seat, the valve shaft

DK 180809 B1 7 and the valve plate being movable along the valve axis between an open position and a closed position, wherein the safety valve is configured so that the valve shaft and the valve plate moves in a downstream direction when moving from the closed position to the open position.

If the pressure inside of the cylinder increases above the closing pressure of the fuel gas valve, the fuel gas valve will be forced open since it is designed with inverted lift direction. However, by using a safety valve with normal lift direction it may be secured that not also the safety valve is forced open, as the valve plate of the safety valve in that situation will be pressed harder against its valve seat.

The valve plate of the safety valve may have a first side and a second side, the second side being opposite to the first side, the valve shaft extending from the first side and a part of the first second side is abutting the valve seat when the safety valve is in the closed position.

In some embodiments the fuel gas nozzle is extending along a nozzle axis and has an inlet for receiving fuel gas and an outlet for delivering fuel gas to the inside of the cylinder, the valve shaft and the valve plate moves a distance d1 along the valve axis when moving from the closed position to the open position, and wherein the fuel gas nozzle has a cross- sectional area at a distance d1 from the inlet along the nozzle axis being smaller than the cross-sectional area of the valve plate.

Consequently, the residual volume of fuel gas captured in the fuel gas nozzle may be lowered, whereby the gas slip may be lowered correspondingly.

In some embodiments the valve plate has a first side and a second side, the valve shaft extending from the first side and the second side facing the outlet of the fuel gas nozzle, wherein the fuel gas valve further comprises a gas displacement element extending from the second side of the valve plate into the fuel gas nozzle.

DK 180809 B1 8 Consequently, the residual volume of fuel gas captured in the fuel gas nozzle may be lowered even further, whereby the gas slip may be lowered correspondingly.

The gas displacement element may taper towards its distal end so as to allow the fuel gas nozzle to decrease in width towards its outlet.

According to a second aspect the invention relates to a a fuel gas valve for a two-stroke uniflow scavenged crosshead internal combustion engine as disclosed in relation to the first aspect, wherein the fuel gas valve comprises a valve shaft extending along a valve axis, a valve plate, and a valve seat, the valve shaft and the valve plate being movable along the valve axis between an open position and a closed position, wherein the fuel gas valve is configured so that the valve shaft and the valve plate moves in a upstream direction when moving from the closed position to the open position.

The different aspects of the present invention can be implemented in different ways including as a two-stroke uniflow scavenged crosshead internal combustion engine and a fuel gas valve as described above and in the following, each yielding one or more of the benefits and advantages described in connection with at least one of the aspects described above, and each having one or more preferred embodiments corresponding to the preferred embodiments described in connection with at least one of the aspects described above and/or disclosed in the dependant claims. Furthermore, it will be appreciated that embodiments described in connection with one of the aspects described herein may equally be applied to the other aspects.

Brief description of the drawings The above and/or additional objects, features and advantages of the present invention, will be further elucidated by the following illustrative and non- limiting detailed description of embodiments of the present invention, with reference to the appended drawings, wherein:

DK 180809 B1 9 Fig. 1 shows schematically a cross-section of a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention.

Fig. 2a-b show schematically a cross-section of a prior art fuel gas valve for a a two-stroke uniflow scavenged crosshead internal combustion engine.

Fig. 3a-b show schematically a cross-section of a fuel gas valve for a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention.

Fig. 4 shows schematically a cross-section of a fuel gas valve for a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention.

Fig. 5 shows schematically a cross-section of a fuel gas valve for a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention.

Fig. 6 shows a schematic drawing of a valve assembly for a fuel gas supply system of a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the present invention.

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

Fig. 1 shows schematically a cross-section of a two-stroke — uniflow scavenged crosshead internal combustion engine 100 for propelling a marine vessel according to an embodiment of the present invention. The two- stroke internal combustion engine 100 comprises a scavenge air 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 comprises a scavenge air inlet 102 arranged in a lower section of the cylinder for providing scavenge

DK 180809 B1 10 air, a piston 103, a cylinder cover 113 arranged on top of the cylinder, an exhaust valve 104 arranged in the cylinder cover 113 and one or more fuel gas valves 105 (only schematically illustrated). The scavenge air inlet 102 is fluidly connected to the scavenge air system. The piston 103 is shown in its lowest position (bottom dead center). The piston 103 has a piston rod connected to a crankshaft (not shown). The piston 103 being movably arranged within the cylinder along a central axis 114 between bottom dead center and top dead center. The fuel gas valve 105 is only shown schematically. The fuel gas valve 105 is arranged at least partly in the cylinder wall between the cylinder cover 113 and the scavenge air inlet 102 and forms part of a fuel gas supply system and is configured to admit fuel gas into the cylinder during the compression stroke enabling the fuel gas to mix with scavenge air from the scavenge air inlet 102 and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited, the fuel gas valve 105 has a fuel gas nozzle, the fuel gas nozzle has one or more nozzle outlets for providing fuel gas to the interior of the cylinder. The fuel gas supply system is fluidly connectable to a fuel gas tank. The fuel gas supply system may further comprises a safety valve (not shown) for each cylinder, where the fuel gas valve 105 is fluidly connectable to the fuel gas tank via the safety valve. The safety valve may be configured to open a short period of time before the fuel gas valve 105 is configured to open and to close a short period of time after the fuel gas valve 105 is configured to close thereby creating a limited period of time where fuel gas from a main fuel gas supply tube can flow through the safety valve to the fuel gas valve 105. This means that the safety valve at normal operation will be activated just as often as the fuel gas valve as it opens and closes immediately before and after, respectively, the opening period of the gas valve 105 where gas is admitted into the cylinder.

The internal combustion engine 100 comprises a dedicated ignition system for igniting the mixture of fuel gas and scavenging air at the end of the compression stroke. As an example, the dedicated ignition system

DK 180809 B1 11 may be a pilot fuel system being capable of injecting a small amount of pilot fuel, e.g. heavy fuel oil or marine diesel oil, accurately measured out so the amount just is able to ignite the mixture of fuel gas and scavenge air such that only the necessary amount of pilot fuel is used.

Such a pilot fuel system would in size be much smaller and more suitable for injecting a precise amount of pilot fuel compared to the dedicated fuel supply system for the alternative fuel, which due to the large size of the components is not suitable for this purpose.

The pilot fuel may be injected in a pre-chamber being fluidly connected to the combustion chamber of the internal combustion engine.

Alternatively, the pilot fuel may be injected in a pre-chamber set being fluidly connected to the combustion chamber of the internal combustion engine.

The fuel gas valve 105 may be configured to inject a fuel gas into the cylinder 101 in the beginning of the compression stroke within O degrees to 130 degrees from bottom dead center, i.e. when the crankshaft has rotated between 0 degrees and 130 degrees from its orientation at bottom dead center.

Preferably the fuel gas valves 105 are configured to start injecting fuel gas after the crankshaft axis has rotated a few degrees from bottom dead center so that the piston has moved past the scavenge air inlets 102 to prevent fuel gas from exiting through the exhaust valve 104 and scavenge air inlets 102. The scavenge air system 111 comprises a scavenge air receiver 110 and an air cooler 106. The exhaust valve is arranged centrally in the cylinder cover and the timing of the exhaust valve may be variable such that the closing and/or opening of the exhaust valve can be optimized e.g. to control the compression ratio and/or the temperature in the cylinder.

The fuel gas valve 105 comprises a valve shaft extending along a valve axis, a valve plate, and a valve seat, the valve shaft and the valve plate being movable along the valve axis between an open position and a closed position.

The fuel gas valve 105 is configured so that the valve shaft and the valve plate moves in an upstream direction when moving from the closed position to the — open position.

DK 180809 B1 12 Figs. 2a-b show schematically a cross-section of a prior art fuel gas valve 200 for a two-stroke internal combustion engine. 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 nozzle outlet 206. The valve shaft 201 and the valve plate 202 are movable between a closed position, where fuel gas is prevented to flow through the fuel gas valve 200, and an open position, where fuel gas is allowed to flow through the fuel gas valve 200. The valve shaft 201 and the valve plate 202 are shown in the closed position in Fig. 2a and in the open position in Fig. 2b. The valve shaft 201 and the valve plate 202 may be movable between the closed position and the open position by means of an actuator (not shown) controlled by a control unit (not shown). The valve shaft 201 and the valve plate 202 moves in a down-stream direction towards the nozzle outlet 206, when moving from the closed position to the open position, whereby the fuel gas nozzle 204 must be designed with an volume 210 in front of the valve plate 202 large enough to accommodate the valve plate when the valve plate is in the open position. However, after the fuel gas valve has closed and the piston 103 has moved past the fuel gas nozzle 206, a significant residual volume of fuel gas is captured in the volume 210 of the fuel gas nozzle. A part of this residual volume will flow / diffuse into the scavenging space below the piston 103, where it will mix with scavenging air. In the next engine cycle, when the piston moves below the scavenging air inlets, the mixture will flow into the cylinder and a part of the mixture will be directed directly out the exhaust valve 104 in the beginning of the scavenging process resulting in a gas slip.

Fig. 3a-b show schematically a cross-section of a fuel gas valve 300 for a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention. The fuel gas valve 300 comprises a valve shaft 301 extending along a valve axis 307, a valve plate 302, a valve seat 303, and a fuel gas nozzle 304 having a nozzle outlet 306 — opening into the cylinder. The valve shaft 301 and the valve plate 302 are movable along the valve axis 307 between a closed position, where fuel gas

DK 180809 B1 13 is prevented to flow through the fuel gas valve 300, and an open position, where fuel gas is allowed to flow through the fuel gas valve 300. The valve shaft 301 and the valve plate 302 are shown in the closed position in Fig. 3a and in the open position in Fig. 3b. The valve plate 302 has a first side and a second side, the valve shaft 301 extending from the first side and the second side facing the fuel gas nozzle 304. The valve shaft 301 and the valve plate 302 may be movable between the closed position and the open position by means of an actuator (not shown) controlled by a control unit (not shown). The fuel gas valve 300 is configured so that the valve shaft 301 and the valve plate 302 moves in an upstream direction away from the nozzle outlet 306 when moving from the closed position to the open position. Consequently, the internal volume of the fuel gas nozzle may be reduced as it no longer needs to accommodate the valve plate 302 when the valve shaft 301 and the valve plate 302 is in the open position, i.e. the fuel gas nozzle 304 may be designed without the volume 210 shown in Figs. 2a-b. Thus, the residual volume of fuel gas left in the fuel gas nozzle when the valve 300 closes may also be reduced which will result in a reduction in the amount of gas slip. The reduced gas slip will further result in a corresponding increase in efficiency. In this embodiment, the fuel gas valve 300 has a valve housing 308, consisting of a single part, where the fuel gas nozzle 304 is formed in the valve housing 308.

Fig. 4 shows schematically a cross-section of a fuel gas valve for a two- stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the invention. The fuel gas valve corresponds to the fuel gas valve shown in Figs. 3a-b with the difference that the valve housing comprising a first part 309 and a second part 310, the fuel gas nozzle 304 and the valve seat 303 being formed in the second part 310 of the valve housing, and the first part 309 of the valve housing and the second part 310 of the valve housing is connected upstream of the valve seat 303.

Fig. 5 shows schematically a cross-section of a fuel gas valve for a two-stroke uniflow scavenged crosshead internal combustion engine

DK 180809 B1 14 according to an embodiment of the invention. The fuel gas valve corresponds to the fuel gas valve shown in Fig. 4 with the difference that the fuel gas valve further comprises a gas displacement element 311 extending from the second side of the valve plate 302 into the fuel gas nozzle 304.

Consequently, the residual volume of fuel gas captured in the fuel gas nozzle 304 may be lowered even further, whereby the gas slip may be lowered correspondingly.

Fig. 6 shows a cross-section of a valve assembly 690 of a fuel gas supply system for a two-stroke uniflow scavenged crosshead internal combustion engine according to an embodiment of the present invention. The valve assembly 690 comprises a fuel gas valve 600 and a safety valve 650, the safety valve 650 has a valve housing 655 with an inlet 656 and an outlet 657, the fuel gas valve 600 has a valve housing 605 with an inlet 607 and an outlet (not shown) formed in a valve nozzle 670. The safety valve 650 comprises a valve shaft 651, a valve plate 652 and a valve seat 653. The valve shaft 651 and the valve plate 652 are movable between a closed position, where fuel gas is prevented to flow through the safety valve 650, and an open position, where fuel gas is allowed to flow through the safety valve 650. The valve shaft 651 and the valve plate 652 are shown in the closed position in Fig. 6. The fuel gas valve 600 comprises a valve shaft 601, a valve plate 602 and a valve seat 603. The valve shaft 601 and the valve plate 602 are movable between a closed position, where fuel gas is prevented to flow through the fuel gas valve 600, and an open position, where fuel gas is allowed to flow through the fuel gas valve 600. The valve shaft 601 and the valve plate 602 are shown in the closed position in Fig. 6. The valve housing of the safety valve 655 is directly connected to the valve housing of the first fuel gas valve 605 so that the outlet of the safety valve 657 is directly connected to the inlet of the first fuel gas valve 607. The valve assembly 690 further comprise a pressure sensor 608 arranged in the volume between the safety valve 650 and the fuel gas valve 600.

DK 180809 B1 15 Moreover, the valve assembly 690 may comprise a position sensor, e.g. an inductive sensor, monitoring the position of the valve shaft 601. An advantage of utilising a pressure sensor compared to an inductive position sensor is that a pressure sensor can verify the tightness of the complete valve assembly and not only the spindle position. Furthermore a single pressure sensor can monitor the function of both the fuel valve and the safety valve at the same time. A position sensor solution will require two separate sensors for monitoring the two valves. The valve housing 605 of the fuel gas valve comprises a first part 609 and a second part 610, the fuel gas nozzle and the valve seat 603 being formed in the second part of the valve housing 610, and the first part of the valve housing 609 and the second part of the valve housing 610 is connected upstream of the valves seat 603. The fuel gas valve 600 is configured so that the valve shaft 601 and the valve plate 602 moves in an upstream direction when moving from the closed position to the open position. The safety valve 650 is configured so that the valve shaft 651 and the valve plate 652 moves in a downstream direction (towards the inlet 607 of the fuel gas valve 600) when moving from the closed position to the open position. Consequently, if the pressure inside of the cylinder increases above the closing pressure of the fuel gas valve 600, the fuel gas valve 600 will be forced open since it is designed with inverted lift direction. However, by using a safety valve 650 with normal lift direction it may be secured that not also the safety valve 650 is forced open, as the valve plate 652 of the safety valve in that situation will be pressed harder against its valve seat 653.

Although some embodiments have been described and shown in detail, the invention is not restricted to them, but may also 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 utilised and structural and functional modifications may be made without departing from the scope of the present invention.

DK 180809 B1 16 In device claims enumerating several means, several of these means can 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

DK 180809 B1 17 Requirements:

A longitudinally flushed two-stroke cross-head internal combustion engine (100) comprising at least one cylinder (101), a cylinder cover (113), a piston (103), a fuel gas supply system connectable to a fuel gas tank, and a purge air system (111), the cylinder (101) has a cylinder wall, the cylinder cover (113) being located 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 Peak dead center, where the purge air system (111) has a purge air inlet (102) located at the bottom of the cylinder (101), the fuel gas supply system comprising a fuel gas valve (105; 300) for the cylinder (101) disposed at least partially in the cylinder wall and configured to closing fuel gas into the cylinder (101) below - the compression stroke via a fuel gas nozzle (304) allowing the fuel gas to mix with the purge air from the purge air inlet (102) and ti allowing the mixture of purge air and fuel gas to be compressed before igniting, where the fuel gas valve (105; 300) comprises a valve rod (301) extending along a valve axis (307), a valve plate (302) and a - valve seat (303), the valve rod (301) and the valve plate (302) being movable along the valve axis (307) between a open position and a closed position, characterized in that the fuel gas valve (105; 300) is arranged at least partially in the cylinder wall at a height below the piston (103) when the piston (103) is at the top dead center, and the fuel gas valve (105; 300) - is configured so that the valve rod (301) and the valve plate (302) move in an upstream direction as they move from the closed position to the open position.

The long-flushed two-stroke cross-head internal combustion engine of claim 1, wherein - the fuel gas nozzle (304) is an integral part of the fuel gas valve (105; 300).

DK 180809 B1 18

A longitudinally flushed two-stroke cross-head internal combustion engine according to claim 2, wherein the fuel gas valve (105; 300) comprises a valve housing (308), the valve housing (308) comprising a first part (309) and a second part (310), wherein - the fuel gas nozzle (304) and the valve housing (303) is formed in the second part (310) of the valve housing (308) and the first part (309) of the valve housing (308) and the second (310) part of the valve housing (308) are connected upstream of the valve seat (303). ).

A longitudinally flushed two-stroke cross-head internal combustion engine according to any one of claims 1 to 3, wherein the fuel gas supply system further comprises a safety valve (650) arranged upstream of the fuel gas valve (105; 300; 600), to which the fuel gas valve (105; 300; 600) can be fluidly connected. the fuel gas tank via the safety valve (650).

The longitudinally flushed two-stroke cross-head internal combustion engine of claim 4, wherein a first sensor is arranged in the volume between the safety valve (650) and the fuel gas valve (105; 300; 600), the first sensor being configured to directly or indirectly detect a pressure change in the volume between the safety valve (650) and the fuel gas valves (105; 300; 600) which indicate a defective fuel gas valve.

A long-flushed two-stroke cross-head internal combustion engine according to claim 4 or 5, wherein the safety valve (650) has a valve housing (655) with an inlet (656) and an> outlet (657), the fuel gas valve (105; 300; 600) has a valve housing (308 ) with an inlet and an outlet, and wherein the valve housing (655) of the safety valve (650) is connected directly to the valve housing (308) of the fuel gas valve (150; 300; 600) so that the outlet (657) of the safety valve (650) is connected directly connected to the inlet (607) of the first fuel gas valve (150; 300; 600).

DK 180809 B1 19

A longitudinally flushed two-stroke cross-head internal combustion engine according to any one of claims 4 to 6, wherein the safety valve (650) comprises a valve stem (651) extending along a valve axis, a valve plate (652) and a valve seat (653), the valve stem (653) 651) and the valve plate (652) are movable along the valve axis between an open position and a closed position, the safety valve (650) being configured so that the valve rod (651) and the valve plate (652) move in a downstream direction as they move from the closed position. position to the open position.

A longitudinally flushed two-stroke cross-head internal combustion engine according to any one of claims 1 to 7, wherein the fuel gas nozzle (304) extends along a nozzle axis and has an inlet for receiving fuel gas and an outlet (306) for supplying fuel gas to the interior of the cylinder. (101), wherein the valve rod (301) and the valve plate (302) move a distance d1 along the valve axis (307) when - they move from the closed position to the open position, and where the fuel gas nozzle (304) has a cross-sectional area at a distance d1 from the inlet along the nozzle axis which is smaller than the cross-sectional area of the valve plate (302).

A longitudinally flushed two-stroke cross-head internal combustion engine according to any one of claims 1 to 8, wherein the valve plate (302) has a first side and a second side, the valve stem (301) extending from the first side and the second side facing the outlet ( 306) of the fuel gas nozzle (304), the fuel gas valve (105; 300; 600) further comprising a gas displacement member (311) extending from the other side of the valve plate (302) into the fuel gas nozzle (304).

A fuel gas valve (105; 300; 600) for a longitudinally flushed two-stroke cross-head internal combustion engine (100) according to any one of claims 1 to 9, - wherein the fuel gas valve (105; 300; 600) comprises a valve rod (301) extending along a valve shaft (307), a valve plate (302) and a valve seat

DK 180809 B1 20 (303), where the valve stem (301) and the valve plate (302) are movable along the valve axis (307) between an open position and a closed position, characterized in that the fuel gas valve (105; 300; 600) is configured so that the valve rod (301) and the valve plate (302) move in an upstream direction as they move from the closed position to the open position.