JP7570978B2 - Internal combustion engine - Google Patents

Description

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

Two-stroke internal combustion engines are used as propulsion engines in marine vessels such as container ships, bulk carriers, and tankers. The reduction of undesirable emissions from internal combustion engines is becoming increasingly important.

An effective way to reduce the amount of undesirable emissions is to switch from fuel oil, e.g. heavy fuel oil (HFO), to fuel gas. The fuel gas can be injected into the cylinder at the end of the compression stroke where it can be immediately ignited, either by the high temperature that the gas in the cylinder achieves 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 to compress the fuel gas prior to injection in order to overcome the high pressure in the cylinder.

However, high pressure gas compressors are 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, when the pressure in the cylinder is significantly lower.

EP 3015679 discloses such a fuel gas valve.

For two-stroke uniflow scavenged internal combustion engines, this requires the fuel gas valve to be located relatively low in the cylinder, making fuel gas valve failure very problematic since fuel gas could be released into the scavenging space below the piston. This could result in too high cylinder pressure causing the cylinder cover to lift in the next engine cycle, or could result in misfire or knocking. Furthermore, detecting fuel gas valve leaks can be difficult, especially if the leak is small, e.g. due to a slightly damaged valve seat area. Small amounts of undetected leaks can also increase methane slip which is harmful to the environment.

Therefore, providing safer internal combustion engines remains a challenge.

According to a first aspect, the present invention relates to a two-stroke uniflow scavenging crosshead internal combustion engine having a plurality of cylinders, each of the plurality of cylinders having a cylinder wall and a scavenging inlet arranged at the bottom of the cylinder, wherein the two-stroke uniflow scavenging internal combustion engine is configured to inject fuel gas into each of the plurality of cylinders via a fuel gas supply system fluidly connectable to a fuel gas tank, the fuel gas supply system comprising, for each cylinder, a first group of fuel gas valves arranged at least partially in the cylinder wall and configured to admit fuel gas into the cylinder during a compression stroke, allowing the fuel gas to mix with the scavenging air and allowing the mixture of scavenging air and fuel gas from the scavenging inlet to be compressed before being ignited, wherein the fuel gas supply system further comprises, for each cylinder, a safety valve arranged upstream of the first group of fuel gas valves, the first group of fuel gas valves being fluidly connectable to the fuel gas tank via the safety valve.

As a result, the delivery of fuel gas to the fuel gas valve can be effectively and quickly stopped. Thus, the amount of fuel gas allowed to flow through a damaged fuel gas valve can be limited, thereby reducing the risk of damage to the engine.

The internal combustion engine is preferably a large slow-speed turbocharged two-stroke crosshead internal combustion engine with uniflow scavenging for propelling marine vessels, with a power of at least 400 kW per cylinder. The combustion engine system may include a turbocharger configured to be driven by exhaust gases generated by the internal combustion engine and to compress the scavenging air. The internal combustion engine may be a dual-fuel engine having an Otto cycle mode when powered by fuel gas and a Diesel cycle mode when powered by an alternative fuel, e.g., heavy fuel 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 injection of pilot fuel when operating in Otto cycle mode to ignite the mixture of fuel gas and scavenging air.

The internal combustion engine may be equipped with a dedicated ignition system, such as a pilot fuel system capable of injecting small amounts of pilot fuel, e.g. heavy fuel oil or marine diesel, precisely dosed so that just the right amount can ignite the fuel gas and scavenging air mixture, so that only the required amount of pilot fuel is used. Such pilot fuel systems are much smaller in size and more suitable for injecting precise amounts of pilot fuel compared to dedicated fuel supply systems for alternative fuels, due to the large size of the components not suitable for this purpose.

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

In some embodiments, the safety valve is configured to open before the first group of fuel gas valves are configured to open and to close after the first group of fuel gas valves are configured to close, thereby creating a limited period of time during which fuel gas is permitted to flow through the safety valve to the first group of fuel gas valves.

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

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

In some embodiments, the fuel gas supply system includes one or more control units operably connected to each of the safety valves and configured for each cylinder to hold the safety valve closed during the time period that the first group of fuel gas valves are closed, whereby pressurized gas is trapped in a volume between the safety valve and the first group of fuel gas valves.

As a result, by monitoring the relatively small volume between the safety valve and the first group of fuel gas valves, for example for pressure or temperature changes, it is possible to detect a malfunctioning fuel gas valve early on, when only traces of fuel gas are leaking through the closed fuel gas valve.

The volume between the safety valve and the first group of fuel gas valves is defined as the volume downstream of the closure member of the safety valve and the closure member of the first group of fuel gas valves, e.g., the volume between the valve plate of the safety valve and the valve plate of the first group of fuel gas valves.

In some embodiments, the two-stroke internal combustion engine further comprises, for each cylinder, a first sensor disposed in a volume between the safety valve and the first group of fuel gas valves, the first sensor configured to directly or indirectly detect a pressure change in the volume between the safety valve and the first group of fuel gas valves indicative of a malfunctioning fuel gas valve.

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

The first sensor may be a pressure sensor configured to directly detect pressure changes. Alternatively, the first sensor may be another sensor configured to indirectly detect pressure changes, such as, for example, a temperature sensor. A second sensor may further be disposed in the volume between the safety valve and the first group of fuel gas valves, for example, 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 operably connected to the first sensor (and possibly the second sensor). The control unit may be configured to monitor the sensor signal received from the first sensor and to issue an alarm if a malfunctioning fuel gas valve is detected, such as, for example, if a pressure drop is detected in the volume between the safety valve and the first group of fuel gas valves, indicating either a damaged valve plate or valve seat, or a stuck valve shaft. The control unit may be configured to take an action in response to the alarm, for example the control unit may ensure that the safety valve of the malfunctioning fuel gas valve is permanently closed, and/or initiate a blowing operation to blow gas out of the fuel gas supply system, and/or control the engine to switch from gas mode to an alternative mode, such as, for example, diesel mode.

In some embodiments, the control unit is configured to keep the relief valve open until after the first group of fuel gas valves have been closed.

As a result, the initial pressure of the fuel gas trapped in the volume between the safety valve and the first group of fuel gas valves is equal to the injection pressure, thereby making small leaks easier to detect.

In some embodiments, the first group of fuel gas valves are positioned along a portion of the cylinder periphery that spans less than 140 degrees, less than 90 degrees, or less than 60 degrees.

As a result, by locating the fuel gas valve(s) of the first group of fuel gas valves along a smaller portion of the circumference, the piping is simpler and the volume between the safety valve and the fuel gas valve(s) of the first group of fuel gas valves can be smaller.

The first group of fuel gas valves preferably consists of a single fuel gas valve, but it may also comprise two or more fuel gas valves.

In some embodiments, for each cylinder, the internal volume of the fuel gas supply system downstream of the safety valve is less than 15 liters, less than 10 liters, or less than 8 liters.

As a result, by keeping the volume downstream of the safety valve low, the amount of fuel gas allowed to leak through a damaged fuel gas valve can be approximately correspondingly low.

The internal volume of the fuel gas supply system downstream of the safety valve is defined as the internal volume of the fuel gas supply system downstream of the closure member of the safety valve, e.g., downstream of the valve plate of the safety valve.

In some embodiments, for each cylinder, the first group of fuel gas valves consists of a first fuel gas valve.

As a result, each fuel gas valve is provided with its own dedicated relief valve. This minimizes the volume downstream of the relief valve and allows for fast and accurate identification of a malfunctioning fuel gas valve.

In some embodiments, the safety valve has a valve housing having an inlet and an outlet, and the first fuel gas valve has a valve housing having an inlet and an outlet, where the valve housing of the safety valve is directly connected to the valve housing of the first fuel gas valve, such that the outlet of the safety valve is directly connected to the inlet of the first fuel gas valve.

As a result, the volume downstream of the safety valve may decrease.

In some embodiments, the valve housing of the safety valve and the valve housing of the first fuel gas valve are integrated, i.e., formed as one element.

In some embodiments, the moving parts of the safety valve are the same as the moving parts of the fuel gas valve.

As a result, maintenance and manufacturing can be simpler.

In some embodiments, for each cylinder, the relief valve is configured to be open for a predetermined period around the time of injection for the first group of fuel gas valves.

In some embodiments, the fuel gas supply system further comprises, for each cylinder of the first group of the plurality of cylinders, a first main fuel gas supply pipe adapted to fluidly connect a fuel gas valve of the first group to a fuel gas tank, a first main safety valve for fluidly connecting the first main fuel gas supply pipe to the fuel gas tank, a first blow-off valve adapted to fluidly connect the first main fuel gas supply pipe to a blow-off system, and one or more control units operably connected to the first main safety valve, the first blow-off valve, and the safety valve of each cylinder of the first group of cylinders, wherein the one or more control units are configured to monitor a status of the fuel gas valve of the first group for each cylinder of the first group of cylinders, and to notify the user of a malfunction of the fuel gas valve when the malfunction of the fuel gas valve occurs.
- Sending a control signal to the malfunctioning fuel gas valve safety valve to control it to close;
sending a control signal to the first main safety valve to control it to close; and sending a control signal to the blow-off valve to control it to open;
wherein the fuel gas supply system is adapted to direct a majority (e.g., at least 80%, at least 90%, or at least 95%) of the fuel gas present in the fuel gas supply system downstream of the first main safety valve through the main fuel gas supply line and the blow-off valve to the blow-off system.

As a result, using the same fuel gas line to supply fuel gas to the fuel gas valve and to empty the fuel gas supply system of fuel gas results in a significantly simpler system, i.e. a dedicated blow-off system to receive fuel gas in the event of an emergency is no longer required.

In some embodiments, the two-stroke internal combustion engine is operable in a first state in which the fuel gas supply system supplies fuel gas to each of the plurality of cylinders, and a second state in which the fuel gas supply system is configured to cut off delivery of fuel gas to at least one of the plurality of cylinders by maintaining a safety valve of at least one of the plurality of cylinders closed.

As a result, the cylinders can be shut off for maintenance, allowing the two-stroke internal combustion engine to operate in gas mode.

According to a second aspect, the present invention relates to a valve assembly for a fuel gas supply system of a two-stroke uniflow scavenging crosshead internal combustion engine as disclosed in relation to the first aspect, comprising a fuel gas valve and a safety valve, the safety valve having a valve housing having an inlet and an outlet, and the fuel gas valve having a valve housing having an inlet and an outlet, wherein the valve housing of the safety valve is directly connected to the valve housing of the fuel gas valve, whereby the outlet of the safety valve is directly connected to the inlet of the fuel gas valve.

The valve housing of the safety valve and the valve housing of the fuel gas valve may be directly connected by placing them against each other, e.g., whereby the valve housing of the safety valve is adjacent to the valve housing of the fuel gas valve. Alternatively, the valve housing of the safety valve and the fuel gas valve may be directly connected by making them as integrated elements, e.g., by molding them (or at least a portion of them) as a combined single element.

In some embodiments, the valve assembly further includes a pressure sensor disposed in the volume between the relief valve and the fuel gas valve.

Different aspects of the present invention may be realized in different ways, including as a two-stroke uniflow scavenging crosshead internal combustion engine and valve assembly as described above and below, each producing one or more of the benefits and advantages described in relation to at least one of the aspects described above, and each having one or more preferred embodiments corresponding to the preferred embodiments described in relation to at least one of the aspects described above and/or disclosed in the dependent claims. Furthermore, it will be recognized that an embodiment described in relation to one of the aspects described herein may be equally applicable to the other aspects.

The above and/or additional objects, features, and advantages of the present invention will be made more apparent from the following illustrative, non-limiting detailed description of embodiments of the present invention, taken in conjunction with the accompanying drawings.

FIG. 1 shows a schematic cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. FIG. 2 shows a schematic cross-section of a fuel gas valve for a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. FIG. 3a shows a schematic cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. FIG. 3b shows a schematic cross-section of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. FIG. 4a shows a schematic representation of a part of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. FIG. 4b shows a schematic representation of a part of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. FIG. 5 shows a schematic diagram of a valve assembly for a fuel gas supply system of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention.

In the following description, reference is made to the accompanying drawings, which show, by way of example, how the invention may be put into practice.

1 shows a schematic cross-section of a two-stroke uniflow scavenging 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 scavenging system 111, an exhaust gas receiver 108, and a turbocharger 109. The two-stroke internal combustion engine has a number of cylinders 101 (only a single cylinder is shown in the cross-section). Each cylinder 101 comprises a scavenging inlet 102 arranged at the bottom of the cylinder for supplying scavenging air, a piston 103, a cylinder cover 113 arranged at the top of the cylinder, an exhaust valve 104 arranged at the cylinder cover 113, and one or more fuel gas valves 105 (only shown diagrammatically). 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 fuel gas valves 105 are only shown diagrammatically. The fuel gas valve 105 is at least partially disposed in the cylinder wall between the cylinder cover 113 and the scavenging air inlet 102, forms part of a fuel gas supply system, and is configured to inject fuel gas into the cylinder during the compression stroke, allowing the fuel gas to mix with the scavenging air from the scavenging air inlet 102 and allowing the mixture of scavenging air and fuel gas to be compressed before being ignited, the fuel gas valve 105 having a fuel gas nozzle, the fuel gas nozzle having one or more nozzle outlets for supplying 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 further comprises a safety valve 112 (only diagrammatically illustrated) for each cylinder, where the fuel gas valve 105 is fluidly connectable to the fuel gas tank via the safety valve 112. The safety valve 112 is 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 during which fuel gas from the main fuel gas supply line 316 can flow through the safety valve 112 to the fuel gas valve 105. This means that the safety valve 112 in normal operation will be activated the same as the fuel gas valve 105, because it opens just before and closes just after the open period of the gas valve 105 during which gas is admitted to the cylinder. The safety valve 112 has a double safety function. Firstly, it ensures that gas admission to the combustion chamber is only possible with the correct admission timing, and secondly, in the event of a failure of the fuel gas valve 105, it can block gas from entering the combustion chamber, thereby ensuring that only a very small amount of gas in the space downstream of the safety valve will enter the combustion chamber. Another benefit of having the relief valve activated with each revolution of the engine is that the relief valve 112 will not jam, which can be a problem for a relief valve that is only activated in the unlikely event of a fault.

The fuel gas valve 105 may be configured to inject fuel gas into the cylinder 101 at the beginning of the compression stroke within 0 to 130 degrees from bottom dead center, i.e., when the crankshaft has rotated between 0 and 130 degrees from its orientation at bottom dead center. Preferably, the fuel gas valve 105 is configured to start injecting fuel gas after the crankshaft axis has rotated a few degrees from bottom dead center so that the piston passes the scavenging inlet 102 to prevent fuel gas from escaping through the exhaust valve 104 and the scavenging inlet 102. 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 variable so that the closing and/or opening of the exhaust valve can be optimized, for example to control the compression ratio and/or temperature in the cylinder.

Figure 2 shows a schematic 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 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 in which fuel gas is prevented from flowing through the fuel gas valve 200, and an open position in which fuel gas is permitted to flow through the fuel gas valve 200. The valve shaft 201 and the valve plate 202 are shown in the closed position in Figure 2. The valve shaft 201 and the valve plate 202 may be movable between the closed and open positions by an actuator (not shown) controlled by a control unit (not shown).

3a shows a schematic diagram of a two-stroke uniflow scavenging crosshead internal combustion engine 300 having a plurality of cylinders 301 according to an embodiment of the present invention. The two-stroke uniflow scavenging internal combustion engine 300 is configured to inject fuel gas into each of the plurality of cylinders via a fuel gas supply system 315 313 316 312 305 fluidly connectable to a fuel gas tank 318. The fuel gas supply system 315 313 316 312 305 comprises, for each cylinder 301, a first group of fuel gas valves 305 configured to admit a controlled amount of fuel gas into the cylinder 301 during the compression stroke, allowing the fuel gas to mix with the scavenging air and allowing the mixture of scavenging air and fuel gas to be compressed before being ignited. The fuel gas supply system 315 313 316 312 305 further comprises, for each cylinder 301, a safety valve 312 arranged upstream of the first group of fuel gas valves 305, the first group of fuel gas valves being fluidly connectable to a fuel gas tank 318 via the safety valve 312. The fuel gas supply system 315 313 316 312 305 further comprises, for each cylinder 301 of the first group of multiple cylinders, a first main fuel gas supply pipe 316 adapted to fluidly connect the first group of fuel gas valves 305 to a fuel gas tank 318, a first main safety valve 315 for fluidly connecting the first main fuel gas supply pipe 316 to the fuel gas tank 318, a first blow-off valve 313 adapted to fluidly connect the first main fuel gas supply pipe 316 to the blow-off system 314, and one or more control units (not shown) operably connected to the first main safety valve 315, the first blow-off valve 313, and the safety valve 312 of each cylinder of the first group of cylinders. The fuel gas tank 318 may be fluidly connected to the first main safety valve 315 through a compressor 317 configured to compress the fuel gas to an injection pressure, for example, between 3 and 40 bar, preferably between 10 and 25 bar. Alternatively, the fuel gas stored in the fuel gas tank 318 may be pressurized at the injection pressure, thereby eliminating the need for a compressor between the fuel gas tank 318 and the first main safety valve 315. The one or more control units monitor the status of the first group of fuel gas valves 305 for each cylinder 301 of the first group of cylinders, and in the event of a malfunction of the fuel gas valve 305:
Sending a control signal to the safety valve 312 of the malfunctioning fuel gas valve to control the safety valve 312 to close;
Sending a control signal to the first main safety valve 315 to control the first main safety valve 315 to close, and Sending a control signal to the blow-off valve 313 to control the blow-off valve 313 to open,
wherein the fuel gas supply system is adapted to direct a majority (e.g., at least 80%, at least 90%, or at least 95%) of the fuel gas present in the fuel gas supply system downstream of the first main safety valve 315 via the main fuel gas supply line 316 and the blow-off valve 313 to the blow-off system, e.g., by also closing the remaining safety valves 312 and/or the remaining fuel gas valves 305. In this embodiment, the first group of cylinders consists of all cylinders, but in other embodiments the first group may consist of fewer, e.g., two or more cylinders. The one or more control units may also send control signals to the first group of fuel gas valves 305 and/or the safety valves 312 of the other cylinders in the first group of cylinders to close and/or keep the valves closed.

3b shows a schematic diagram of a two-stroke uniflow scavenging crosshead internal combustion engine 300 according to an embodiment of the present invention. The engine 300 is similar to the engine shown in FIG. 3a with the difference that the fuel gas supply system further comprises, for each cylinder 301, a second group of fuel gas valves 305', a second safety valve 312' arranged upstream of the second group of fuel gas valves 305', and the second group of fuel gas valves 305' are fluidly connectable to a fuel gas tank 318 via the second safety valve 312'. The fuel gas supply system further includes, for each cylinder 301 of the first group of multiple cylinders, a second main fuel gas supply pipe 316' adapted to fluidly connect the second group of fuel gas valves 305' to the fuel gas tank 318, a second main safety valve 315' for fluidly connecting the second main fuel gas supply pipe 316' to the fuel gas tank 318, and a second blow-off valve 313' adapted to fluidly connect the second main fuel gas supply pipe 316' to the blow-off system 314'.

4a shows a schematic of a part of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. A cylinder 401 and a part of a fuel gas supply system 412 405 are shown. The fuel gas supply system comprises a first group of fuel gas valves 405 configured for the cylinder 401 to inject fuel gas into the cylinder. In this embodiment, the first group of fuel gas valves 405 consists of a single fuel gas valve 405. The fuel gas supply system further comprises a safety valve 412 arranged upstream of the fuel gas valve 405 for the cylinder 401, whereby the fuel gas valve 405 is fluidly connectable to a fuel gas tank via the safety valve 412. The fuel gas valve 405 is operably connected to a first control unit 320 configured to open and close the fuel gas valve 405. Correspondingly, the safety valve is operably connected to a second control unit 319 configured to open and close the safety valve 412. However, in other embodiments, both the fuel gas valve and the relief valve may be operably connected to the same control unit.

4b shows a schematic of a portion of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. A cylinder 401 and a portion of a fuel gas supply system 412 405 430 are shown. The fuel gas supply system comprises a first group of fuel gas valves 405 430 configured for injecting fuel gas into the cylinder 401. In this embodiment, the first group of fuel gas valves 405 430 comprises a first fuel gas valve 405 and a second fuel gas valve 430. The fuel gas supply system further comprises a safety valve 412 arranged upstream of the first group of fuel gas valves 405 430 for the cylinder 401, such that the first group of fuel gas valves 405 430 are fluidly connectable to a fuel gas tank via the safety valve 412. The first group of fuel gas valves are arranged along a portion of the circumference 421, which in this concrete embodiment is approximately 55 degrees. However, the first group of fuel gas valves may include any number of fuel gas valves, for example arranged around the entire circumference to form a circular nozzle ring. The fuel gas valves may be poppet, ball, butterfly, or rotary valves that open inwardly or outwardly, or other suitable valves.

5 shows a schematic diagram of a valve assembly 690 for a fuel gas supply system of a two-stroke uniflow scavenging crosshead internal combustion engine according to an embodiment of the present invention. The valve assembly 690 includes a fuel gas valve 600 and a safety valve 650, the safety valve 650 having a valve housing 655 with an inlet 656 and an outlet 656, and the fuel gas valve 600 having a valve housing 605 with an inlet 607 and an outlet 606 formed in a valve nozzle 604. The safety valve 650 includes 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 in which fuel gas is prevented from flowing through the safety valve 650 and an open position in which fuel gas is permitted to flow through the safety valve 650. The valve shaft 651 and the valve plate 652 are shown in the open position in FIG. 5. The fuel gas valve 600 includes 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 in which fuel gas is prevented from flowing through the fuel gas valve 600 and an open position in which fuel gas is permitted to flow through the fuel gas valve 600. The valve shaft 651 and the valve plate 602 are shown in the open position in FIG. 5. The safety valve housing 655 is directly connected to the first fuel gas valve housing 605 by forming the safety valve housing 655 and a portion of the fuel gas valve housing 605 as an integral element. The valve assembly 690 further includes a pressure sensor 608 disposed in a volume 680 between the safety valve 650 and the fuel gas valve 600.

Additionally, the valve assembly 690 may include a position sensor, such as, for example, an inductive sensor, that monitors the position of the valve shaft 601. The advantage of utilizing a pressure sensor compared to an inductive position sensor is that the pressure sensor can verify the tightness of the entire valve assembly, not just the spindle position. Furthermore, a single pressure sensor can simultaneously monitor the function of both the fuel valve and the relief valve. A position sensor solution would require two separate sensors to monitor the two valves.

Pressure monitoring can be used in control systems to adjust injection parameters and/or in engine safety strategies.

Although several embodiments have been described and illustrated 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.

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

It should be emphasized that as used in this specification, the term "comprises/comprising" specifies the presence of stated features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
The invention as originally claimed in the present application is set forth below.
[1] A two-stroke uniflow scavenging crosshead internal combustion engine having a plurality of cylinders, each of the plurality of cylinders having a cylinder wall and a scavenging inlet arranged at a bottom of the cylinder, wherein the two-stroke uniflow scavenging crosshead internal combustion engine is configured to inject fuel gas into each of the plurality of cylinders via a fuel gas supply system fluidly connectable to a fuel gas tank, the fuel gas supply system comprising, for each cylinder, a first group of fuel gas valves arranged at least partially in the cylinder wall and configured to admit fuel gas into the cylinder during a compression stroke, allowing the fuel gas to mix with scavenging air from the scavenging inlet, and allowing the mixture of scavenging air and fuel gas to be compressed before being ignited;
A two-stroke uniflow scavenging crosshead internal combustion engine, characterized in that the fuel gas supply system further comprises a safety valve arranged upstream of the first group of fuel gas valves for each cylinder, and the first group of fuel gas valves are fluidly connectable to the fuel gas tank via the safety valve.
[2] The two-stroke uniflow scavenging crosshead internal combustion engine of [1], wherein the safety valve is configured to open before the first group of fuel gas valves are configured to open and to close after the first group of fuel gas valves are configured to close, thereby creating a limited period of time during which fuel gas is permitted to flow through the safety valve to the first group of fuel gas valves.
[3] The two-stroke uniflow scavenging crosshead internal combustion engine of [1] or [2], wherein the fuel gas supply system comprises one or more control units operably connected to each of the safety valves and configured for each cylinder to keep the safety valves closed during the time period when the first group of fuel gas valves are closed, whereby pressurized gas is trapped in a volume between the safety valve and the first group of fuel gas valves.
[4] The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to [3], further comprising a pressure sensor for each cylinder arranged in a volume between the safety valve and the first group of fuel gas valves.
[5] The two-stroke uniflow scavenging crosshead internal combustion engine of any one of [1] to [4], wherein the first group of fuel gas valves are arranged along a portion of the circumference of the cylinder that spans less than 140 degrees, less than 90 degrees, or less than 60 degrees.
[6] The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to [5], wherein for each cylinder, the internal volume of the fuel gas supply system downstream of the safety valve is less than 15 liters, less than 10 liters, or less than 8 liters.
[7] A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to [6], wherein for each cylinder, the first group of fuel gas valves consists of a first fuel gas valve.
[8] A two-stroke uniflow scavenging crosshead internal combustion engine as described in [7], wherein the safety valve has a valve housing having an inlet and an outlet, and the first fuel gas valve has a valve housing having an inlet and an outlet, and the valve housing of the safety valve is directly connected to the valve housing of the first fuel gas valve, whereby the outlet of the safety valve is directly connected to the inlet of the first fuel gas valve.
[9] The fuel gas supply system further comprises, for each cylinder of a first group of the plurality of cylinders, a first main fuel gas supply pipe adapted to fluidly connect a fuel gas valve of the first group to the fuel gas tank, a first main safety valve for fluidly connecting the first main fuel gas supply pipe to the fuel gas tank, a first blow-off valve adapted to fluidly connect the first main fuel gas supply pipe to a blow-off system, and one or more control units operably connected to the first main safety valve, the first blow-off valve, and the safety valve of each cylinder of the first group of cylinders, wherein the one or more control units monitor a status of the fuel gas valve of the first group for each cylinder of the first group of cylinders, and in the event of a malfunction of the fuel gas valve,
Sending a control signal to the safety valve of the malfunctioning fuel gas valve to control the safety valve to close;
sending a control signal to the first main relief valve to control the first main relief valve to close; and
Sending a control signal to the blow-off valve to control the blow-off valve to open;
It is structured as follows:
wherein the fuel gas supply system is adapted to direct a majority (e.g., at least 80%, at least 90%, or at least 95%) of the fuel gas present in the fuel gas supply system downstream of the first main safety valve through the main fuel gas supply line and the blow-off valve to the blow-off system.
[1] to [8]. A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of the above.
[10] The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of [1] to [9], wherein the two-stroke uniflow scavenging crosshead internal combustion engine is operable in a first state in which the fuel gas supply system supplies fuel gas to each of the plurality of cylinders, and a second state in which the fuel gas supply system is configured to cut off the delivery of fuel gas to at least one of the plurality of cylinders by keeping the safety valve of the at least one cylinder closed.
[11] A valve assembly for a fuel gas supply system of a two-stroke uniflow scavenging crosshead internal combustion engine described in any one of [1] to [10], comprising a fuel gas valve and a safety valve, the safety valve having a valve housing having an inlet and an outlet, and a first fuel gas valve having a valve housing having an inlet and an outlet, wherein the valve housing of the safety valve is directly connected to the valve housing of the fuel gas valve, whereby the outlet of the safety valve is directly connected to the inlet of the fuel gas valve.

Claims (11)

A two-stroke uniflow scavenging crosshead internal combustion engine having a plurality of cylinders, each of the plurality of cylinders having a cylinder wall and a scavenging inlet arranged at a bottom of the cylinder, wherein the two-stroke uniflow scavenging crosshead internal combustion engine is configured to inject fuel gas into each of the plurality of cylinders via a fuel gas supply system fluidly connectable to a fuel gas tank, the fuel gas supply system comprising, for each cylinder, a first group of fuel gas valves arranged at least partially in the cylinder wall and configured to admit fuel gas into the cylinder during a compression stroke, allowing the fuel gas to mix with scavenging air from the scavenging inlet and allowing the mixture of scavenging air and fuel gas to be compressed before being ignited;
the fuel gas supply system further comprises, for each cylinder, a safety valve arranged upstream of the first group of fuel gas valves, the first group of fuel gas valves being fluidly connectable to the fuel gas tank via the safety valve;
1. A two-stroke uniflow scavenged crosshead internal combustion engine, wherein the fuel gas supply system is configured to provide fuel gas at an injection pressure to the safety valve, the engine further comprising one or more control units, the one or more control units configured to keep the safety valve open until after a first group of one or more fuel gas valves are closed, the first group of one or more fuel gas valves are fluidly connectable to the fuel gas tank via the safety valve without any valve being disposed between the safety valve and the first group of one or more fuel gas valves, and a pressure in a volume between the safety valve and the first fuel gas valve equals the injection pressure when both the safety valve and the first fuel gas valve are closed . The two-stroke uniflow scavenging crosshead internal combustion engine of claim 1, wherein the safety valve is configured to open before the first group of fuel gas valves are configured to open and to close after the first group of fuel gas valves are configured to close, thereby creating a limited period of time during which fuel gas is permitted to flow through the safety valve to the first group of fuel gas valves. The two-stroke uniflow scavenging crosshead internal combustion engine of claim 1 or 2, wherein the fuel gas supply system comprises one or more control units operably connected to each of the safety valves and configured for each cylinder to keep the safety valves closed during the time period when the first group of fuel gas valves are closed, whereby pressurized gas is trapped in a volume between the safety valve and the first group of fuel gas valves. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 3, further comprising a pressure sensor arranged in a volume between the safety valve and the first group of fuel gas valves for each cylinder. 5. A two-stroke uniflow scavenging crosshead internal combustion engine as claimed in any one of claims 1 to 4, wherein the first group of fuel gas valves are arranged along a portion of the circumference of the cylinder that spans less than 140 degrees. A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 5, wherein for each cylinder the internal volume of the fuel gas supply system downstream of the safety valve is less than 15 litres. A two-stroke uniflow scavenging crosshead internal combustion engine as described in any one of claims 1 to 6, wherein for each cylinder, the first group of fuel gas valves consists of a first fuel gas valve. The two-stroke uniflow scavenging crosshead internal combustion engine of claim 7, wherein the safety valve has a valve housing having an inlet and an outlet, the first fuel gas valve has a valve housing having an inlet and an outlet, and the valve housing of the safety valve is directly connected to the valve housing of the first fuel gas valve, whereby the outlet of the safety valve is directly connected to the inlet of the first fuel gas valve. The fuel gas supply system further comprises, for each cylinder of a first group of the plurality of cylinders, a first main fuel gas supply pipe adapted to fluidly connect a fuel gas valve of the first group to the fuel gas tank, a first main safety valve for fluidly connecting the first main fuel gas supply pipe to the fuel gas tank, a first blow-off valve adapted to fluidly connect the first main fuel gas supply pipe to a blow-off system, and one or more control units operably connected to the first main safety valve, the first blow-off valve, and the safety valve of each cylinder of the first group of cylinders, wherein the one or more control units are configured to monitor a status of the fuel gas valve of the first group for each cylinder of the first group of cylinders, and to notify the user of a malfunction of the fuel gas valve when a malfunction of the fuel gas valve occurs.
Sending a control signal to the safety valve of the malfunctioning fuel gas valve to control the safety valve to close;
sending a control signal to the first main safety valve to control the first main safety valve to close; and sending a control signal to the blow-off valve to control the blow-off valve to open.
It is structured as follows:
wherein the fuel gas supply system is adapted to direct a majority (e.g., at least 80%, at least 90%, or at least 95%) of the fuel gas present in the fuel gas supply system downstream of the first main safety valve through the main fuel gas supply line and the blow-off valve to the blow-off system.
A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 8. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 9, wherein the two-stroke uniflow scavenging crosshead internal combustion engine is operable in a first state in which the fuel gas supply system supplies fuel gas to each of the plurality of cylinders, and a second state in which the fuel gas supply system is configured to cut off the delivery of fuel gas to at least one of the plurality of cylinders by keeping the safety valve of at least one of the plurality of cylinders closed. A valve assembly for a fuel gas supply system of a two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 10, comprising a fuel gas valve and a safety valve, the safety valve having a valve housing having an inlet and an outlet, and a first fuel gas valve having a valve housing having an inlet and an outlet, wherein the valve housing of the safety valve is directly connected to the valve housing of the fuel gas valve, whereby the outlet of the safety valve is directly connected to the inlet of the fuel gas valve.

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