DK201970744A1

DK201970744A1 - Internal combustion engine

Info

Publication number: DK201970744A1
Application number: DKPA201970744A
Authority: DK
Inventors: Nikolaos Kourtidis
Original assignee: Man Energy Solutions Filial Af Man Energy Solutions Se Tyskland
Priority date: 2019-12-02
Filing date: 2019-12-02
Publication date: 2020-10-23

Abstract

Disclosed is a two-stroke uniflow scavenged crosshead internal combustion engine comprising a cylinder, and a fuel gas supply system. The fuel gas supply system comprises a main fuel gas supply tube for fluidly connecting one or more fuel gas valves with a fuel gas tank, the main fuel gas supply tube being provided with a gas pressure regulation valve. The main fuel gas tube is further provided with a by-pass fuel gas tube allowing the fuel gas to by-pass the gas pressure regulation valve, a first part of the fuel gas supply system being configured to be arranged in a no gas zone and a second part of the fuel gas supply system being configured to be arranged in a gas tolerated zone. The fuel gas supply system is configured to empty the fuel gas in the first part through the main fuel gas supply tube.

Description

DK 2019 70744 A1 1 Title Internal combustion engine 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 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 un-wanted 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 large gas compressors for compressing the fuel — gas prior to injection to overcome the large pressure in the cylinders.

The large gas compressors are however expensive and complex to manufacture and maintain. One way to avoid the need of large 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.

Injection of fuel gas in the beginning of the compression stroke requires fine tuning of the injection pressure of the fuel gas for good performance. This is typically achieved by a gas pressure regulation valve arranged within the engine room.

DK 2019 70744 A1 2 For gas engines it is a requirement that the fuel gas supply system can be fast and effectively vented in the event of a gas shutdown e.g. due to a malfunction, an engine shutdown or a shift from gas mode to fuel oil mode if the engine is a dual-fuel engine.

However, providing the fuel gas supply system with effective venting capabilities increases the complexity of the fuel gas supply system.

The increased complexity of the fuel gas supply system increases the cost and further the risk of design errors.

Thus, it remains a problem to provide an engine having a simpler

— fuel gas supply system that effectively and reliably can be vented in the event of a gas shutdown.

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, 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 between bottom dead center and top dead center, the scavenge air system having a scavenge air inlet arranged at the bottom of the cylinder, wherein the two-stroke internal combustion engine is configured to inject into the least one cylinder a fuel gas via the fuel gas supply system, the fuel gas supply system comprising for

— the at least one cylinder one or more fuel gas valves arranged at least partly in the cylinder wall and configured to inject fuel gas into the cylinder during the compression stroke enabling the fuel gas to mix with scavenge air and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited, wherein the fuel gas supply system comprises a main fuel gas

— supply tube for fluidly connecting the one or more fuel gas valves of the at least one cylinder with a fuel gas tank, the main fuel gas supply tube being

DK 2019 70744 A1 3 provided with a gas pressure regulation valve, wherein the main fuel gas tube is further provided with a by-pass fuel gas tube allowing the fuel gas to by- pass the gas pressure regulation valve, a first part of the fuel gas supply system being configured to be arranged in a no gas zone and a second part of the fuel gas supply system being configured to be arranged in a gas tolerated zone, and wherein in the event of a gas shutdown the fuel gas supply system is configured to empty the fuel gas in the first part of the fuel gas supply system through the main fuel gas supply tube.

By providing the fuel gas supply system with a by-pass fuel gas — tube functionality allowing the fuel gas to by-pass the gas pressure regulation valve, the gas in the first part of the fuel gas supply system may effectively and securely be vented via the main fuel gas supply tube even if the gas pressure regulation valve malfunctions. This will further allow all blowout tubes to be arranged outside of the engine room where the gas slip tolerances are less strict making the design simpler and inherently safer.

The main fuel gas supply tube may comprise a plurality of sections e.g. connected by flanges.

A ‘no gas zone’ is a zone where no gas slip is tolerated even in the event of a failure. This may be achieved by providing gas tubes e.g. the main fuel gas tube, with a double wall having a pressurized space between the walls. By monitoring the pressurized space for a pressure drop and gas, gas slip can in theory only happen by a simultaneous failure of both the inner and outer wall.

A ‘gas tolerated zone’ is a zone where gas slip is tolerated in the event of a failure. Thus in the ‘gas tolerated zone’ gas tube e.g. the main fuel gas supply tube, may be single walled.

The engine room is typically a no gas zone whereas other rooms comprising elements of the fuel gas supply system typically are gas tolerated zones.

The gas pressure regulation valve and the by-pas fuel gas tube may be configured to be arranged in a no gas zone.

DK 2019 70744 A1 4 The by-pass fuel gas tube may be provided with a shut-off valve or it may always allow a flow of gas through.

The by-pass fuel gas tube may be configured to be arranged in a no gas zone.

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 an 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.

The internal combustion engine preferably comprises a plurality of cylinders e.g. between 4 and 14 cylinders.

The internal combustion engine further comprises for each cylinder of the plurality of cylinders a cylinder cover, an exhaust valve, a piston, a fuel gas valve, and a scavenge air inlet.

The fuel gas supply system is preferably configured to inject the fuel gas via one or more fuel gas valves under sonic conditions, i.e. a velocity equal to the speed of sound, i.e. a constant velocity.

Sonic conditions may be achieved when the pressure drop ratio across the nozzle throat (minimum area of cross section) is larger than approximately two.

In some embodiments the one or more fuel gas valves are configured to inject a fuel gas into the cylinder during the compression stroke — within O 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.

The one or more fuel gas valves are arranged at least partly in the cylinder wall between top dead center and bottom dead center, preferably ina position above the scavenge air inlet.

The one or more fuel gas valves may comprise a nozzle arranged in the cylinder wall for injecting fuel gas into

DK 2019 70744 A1 the cylinder. The other parts of the fuel gas valve (other than the nozzle) may be arranged outside the cylinder wall. Examples of fuel gases are Liquefied Natural Gas (LNG), methane, ethane, biogas and Liquefied Petroleum Gas (LPG).

5 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 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 directly into the combustion chamber of the internal combustion engine or in a pre-chamber being fluidly connected to the combustion chamber. Alternatively, the mixture of fuel gas and scavenge air may by ignited by means comprising a spark plug, a laser igniter The gas pressure regulation valve may comprise an actuator configured to modify the flow-resistance of the gas pressure regulation valve, whereby the gas pressure may be controlled. The gas pressure regulation valve may further comprise a control unit and a first sensor, where the control unit is communicatively connected to both the first sensor and the actuator and configured to control the actuator based on sensor data received from — the first sensor. The control unit is preferably further communicatively connected to a central engine control unit. The first sensor may be configured to detect pressure, temperature, and / or flow downstream and / or upstream of the gas pressure regulation valve. Preferably the first sensor is configured to detect pressure and temperature downstream of the gas pressure regulation valve.

DK 2019 70744 A1 6 A gas shutdown may be an engine failure, an engine shutdown and / or a shift from gas mode to fuel oil mode if the engine is a dual-fuel engine.

In some embodiment the by-pass fuel gas tube is provided with a first shut-off valve having an open state and a closed state, the fuel gas supply system being configured to keep the first shut-off valve in the closed state under normal operation to prevent flow of gas through the by-pass fuel gas tube and in the event of a gas shutdown open the first shut-off valve allowing fuel gas to flow through the by-pass fuel gas tube.

Consequently by providing the by-pass fuel gas tube with a shut- off valve, gas flow through by-pass fuel gas tube may be prevented during normal engine operation, whereby the gas pressure regulation valve may more effectively control the gas pressure.

This will further allow the diameter of the by-pass fuel gas tube to be increased without decreasing the effectiveness of the gas pressure regulation valve whereby faster emptying of the fuel gas may be achieved.

In some embodiment the fuel gas supply system further comprises a first blowout tube fluidly connected to the main fuel gas tube via a second shut-off valve having an open state and a closed state, the first blowout tube being fluidly connected to the main fuel gas tube upstream of the gas pressure regulation valve, the fuel gas supply system being configured to keep the second shut-off valve in the closed state under normal operation to prevent flow of gas through the first blowout tube and in the event of a gas shutdown open the second shut-off valve allowing fuel gas to — exit the fuel gas supply system via the first blowout tube.

In some embodiments the first blowout tube is configured to be arranged in a gas tolerated zone.

In some embodiments the fuel gas supply system further comprises a second blowout tube fluidly connected to the main fuel gas tube via a third shut-off valve having an open state and a closed state, the second blowout tube being fluidly connected to the main fuel gas tube upstream of

DK 2019 70744 A1 7 the first blow out tube, the fuel gas supply system being configured to keep the third shut-off valve in the closed state under normal operation to prevent flow of gas through the second blowout tube and in the event of a gas shutdown open the third shut-off valve allowing fuel gas to exit the fuel gas — supply system via the second blowout tube.

In some embodiments the second blowout tube is configured to be arranged in a gas tolerated zone.

In some embodiments the main fuel gas supply tube is provided with a fourth shut-off valve arranged between the first blowout tube and the second blowout tube and a fifth shut-off valve arranged upstream of the second blowout tube, the fourth shut-off valve and the fifth shut-off valve have an open state and a closed state, the fuel gas supply system being configured to keep the fourth shut-off valve and the fifth shot-off valve in the open state under normal operation to allow fuel gas the flow through the main fuel gas supply tube and in the event of a gas shutdown close the fourth shut-off valve and the fifth shut-off valve.

In some embodiments the fuel gas supply system comprises for each cylinder a fuel gas supply tube fluidly connecting the main fuel gas supply tube to the one or more fuel gas valves of each cylinder and wherein the fuel gas supply system is configured to in the event of a gas shutdown empty substantially all fuel gas in the main fuel gas supply tube downstream of the first blowout tube through the first blowout tube.

In some embodiments the by-pass fuel gas tube has an internal diameter being at least 80% of the internal diameter of the part of the main — fuel gas supply tube being arranged inside the engine room.

In some embodiments the gas pressure regulation valve and the by-pass fuel gas tube is integrated into a metal block having an inlet connected with a first section of the main fuel gas supply tube and an outlet connected with a second section of the main fuel gas supply tube.

In some embodiments the first and second section of the main fuel gas tube have an inner wall and an outer wall, the inlet of the metal block

DK 2019 70744 A1 8 is configured to establish a fluid tight seal with both the outer wall and the inner wall of the first section of the main fuel gas supply tube, and the outlet of the metal block is configured to establish a fluid tight seal with both the outer wall and the inner wall of the second section of the main fuel gas — supply tube.

Consequently, as channels formed in metal blocks generally are perceived as being fluidly tight and in use indestructible, a simple way of configuring the gas pressure regulation valve and the by-pass fuel gas tube for a no gas zone is provided. This solution has shown to be significant simpler than a double walled solutions. In some embodiments, the metal block is obtained by the process comprising the steps of: e obtaining a solid metal block, e drilling in the solid metal block, from the outside, a first hole having a first opening forming the inlet and a second opening forming the outlet, e drilling one or more times in the solid metal block from the outside a by-pass channel by-passing a central portion of the first hole thereby forming the by-pass fuel gas tube, e arranging a gas pressure regulation valve in the central portion of the first hole, and e optionally, arranging a shut-off valve in the by-pass fuel gas tube. In some embodiments the metal block further comprises a pressure sensor and a control unit, the control unit being communicatively connected to the pressure sensor and an actuator of the pressure regulation valve, the actuator being configured to modify a variable flow resistance in the pressure regulation valve, the control unit being configured to control the actuator based on sensor signals received from the pressure sensor.

Above and below the terms ‘upstream’ and ‘downstream’ are used to describe the location of elements of the fuel gas supply system. The terms refer to the direction of gas flow during normal gas operation and not the direction of gas flow when the fuel gas supply system is being vented.

DK 2019 70744 A1 9 Thus in general, if a first element of the fuel gas supply system is downstream of a second element, the first element will be closer to the one or more fuel gas valves. Above and below the term ‘normal operation’ is used to describe normal gas operation. 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: Fig. 1 shows schematically a cross-section of a two-stroke internal combustion engine according to an embodiment of the invention. Fig. 2a-c show schematically two-stroke internal combustion engines according to embodiments. Fig. 3 shows schematically a two-stroke internal combustion engines according to embodiments of the invention. Figs. 4ab illustrate how a metal block having the gas pressure regulation valve and the by-pass fuel gas tube integrated may be manufactured according to an embodiment of the 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. 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 large low-speed turbocharged two-stroke crosshead internal combustion engine with uniflow scavenging 100 for propelling a marine vessel according to an embodiment of the present invention. The engine 100 comprises a scavenge air system

DK 2019 70744 A1 10 111, an exhaust gas receiver 108, a fuel gas supply system, and a turbocharger 109. The engine has a plurality of cylinders 101 (only a single cylinder is shown in the cross-section). Each cylinder 101 has a cylinder wall 115 and comprises a scavenge air inlet 102 arranged at the bottom of the cylinder 101. The engine further comprises for each cylinder a cylinder cover 112 and a piston 103. The cylinder cover 112 being arranged on top of the cylinder 101 and having an exhaust valve 104. The piston 103 being movably arranged within the cylinder along a central axis 113 between bottom dead center and top dead center.

The fuel gas supply system comprises one or

— more fuel gas valves 105 (only schematically shown) configured to inject fuel gas into the cylinder 101 during the compression stroke enabling the fuel gas to mix with scavenge air and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited.

The fuel gas valves 105 are arranged at least partly in the cylinder wall between the cylinder cover 112 and the scavenge air inlet 102. The fuel gas supply system comprises a main fuel gas supply tube (not shown) for fluidly connecting the fuel gas valves 105 of the at least one cylinder with a fuel gas tank.

The main fuel gas tube being provided with a gas pressure regulation valve (not shown). The main fuel gas tube is further provided with a by-pass fuel gas tube (not shown)

allowing the fuel gas to by-pass the gas pressure regulation valve wherein the fuel gas system in the event of a gas shutdown is configured to empty the fuel gas in the fuel gas supply system through the main fuel gas supply tube.

The engine further comprises a pre-chamber 114 at least partly arranged in the cylinder wall 115, the pre-chamber 114 opening into the cylinder through

— a first opening formed in the cylinder wall, the pre-chamber being configured to ignite the mixture of scavenge air and fuel gas in the cylinder 101. The pre- chamber may alternatively arranged in the cylinder cover 112. 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 fuel gas valves 105 are configured to inject fuel gas into the cylinder during the compression

DK 2019 70744 A1 11 stroke enabling the fuel gas to mix with scavenge air and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited. The scavenge air system 111 comprises a scavenge air receiver 110 and an air cooler 106. The fuel gas valves 105 may be configured to inject a fuel gas into the cylinder 101 in the beginning of the compression stroke within 0 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 engine 100 is preferably 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 alternative fuel supply system for injecting the alternative fuel. Thus optionally the engine 100 further comprise one or more fuel injectors 116 arranged in the cylinder cover 112 forming part of an alternative fuel supply system. When the engine 100 runs on the alternative fuel the fuel injectors 116 are configured to inject the alternative fuel e.g. heavy fuel oil at the end of the compression stroke under high pressure.

Fig. 2a shows schematically a two-stroke internal combustion engines according to an embodiment of the invention. The engine comprises atleast one cylinder, a cylinder cover, a piston, a fuel gas supply system, 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 between bottom dead center and top dead center. The two-stroke internal combustion engine is configured to inject into the least one cylinder a fuel gas via the fuel gas supply system, the fuel gas supply system comprising for the at least one cylinder one or more

DK 2019 70744 A1 12 fuel gas valves arranged at least partly in the cylinder wall and configured to inject fuel gas into the cylinder during the compression stroke enabling the fuel gas to mix with scavenge air and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited. Only parts of the fuel gas supply system 201-204, 211-213 are shown in detail, the remaining parts of the engine are only schematically illustrated by the box 200. The remaining parts of the engine 200 may be similar to the parts shown in Fig. 1. The fuel gas supply system comprises a main fuel gas supply tube 201 for fluidly connecting the one or more fuel gas valves of the at least one cylinder with a fuel gas tank 214. The main fuel gas supply tube 201 is provided with a gas pressure regulation valve 202 and a by-pass fuel gas tube 203 allowing the fuel gas to by-pass the gas pressure regulation valve 202. A part of the fuel gas supply system is arranged in a no gas zone 220 and a part is arranged in a gas tolerated zone 230. The division between the two zone 230 220 is illustrated with the dotted line 210. The fuel gas supply system is in the event of a gas shutdown configured to empty the fuel gas in the fuel gas supply system arranged in the no gas zone 220 through the main fuel gas supply tube 201. The by-pass fuel gas tube 203 may optionally be provided with a first shut-off valve 204 having an open state and a closed state, the fuel gas supply system being configured to keep the first shut-off valve 204 in the closed state under normal operation to prevent flow of gas through the by- pass fuel gas tube 203 and in the event of a gas shutdown open the first shut-off valve 204 allowing fuel gas to flow through the by-pass fuel gas tube

203. The fuel gas supply system comprises further a first blowout tube 211 fluidly connected to the main fuel gas tube 201 via a second shut-off valve 212 having an open state and a closed state, the first blowout tube 211 being fluidly connected to the main fuel gas tube 201 upstream of the gas pressure regulation valve 202, the fuel gas supply system being configured to keep the second shut-off valve 212 in the closed state under normal operation to prevent flow of gas through the first blowout tube 211 and in the event of a

DK 2019 70744 A1 13 gas shutdown open the second shut-off valve 212 allowing fuel gas to exit the fuel gas supply system via the first blowout tube 211. By providing the main fuel gas tube 201 with the by-pass fuel gas tube 203 bypassing the gas pressure regulation valve 202, gas may effectively and safely be emptied out of the no gas zone 220 through the main fuel gas tube 201 even in the event of a major failure of the gas pressure regulation valve 202. Thus, in contrast to prior systems, there is no need for blowout tubes in the no gas zone 220. This may lower the complexity and cost of the fuel gas supply system.

Fig. 2b shows schematically a two-stroke internal combustion engines according to an embodiment of the invention. The fuel gas supply system comprises in addition to the element of the fuel gas supply system disclosed in relation to Fig. 2a, a second blowout tube 215 fluidly connected to the main fuel gas tube 201 via a third shut-off 218 valve having an open — state and a closed state, the second blowout tube 218 being fluidly connected to the main fuel gas tube 201 upstream of the first blowout tube 211, the fuel gas supply system being configured to keep the third shut-off valve 218 in the closed state under normal operation to prevent flow of gas through the second blowout tube 215 and in the event of a gas shutdown open the third shut-off valve 218 allowing fuel gas to exit the fuel gas supply system via the second blowout tube 215. The main fuel gas supply tube 201 is further provided with a fourth shut-off valve 219 arranged between the first blowout tube 211 and the second blowout tube 215 and a fifth shut-off valve 213 arranged upstream of the second blowout tube 215, the fourth shut-off valve 219 and the fifth shut-off valve 213 have an open state and a closed state, the fuel gas supply system being configured to keep the fourth shut-off valve 219 and the fifth shut-off valve 213 in the open state under normal operation to allow fuel gas the flow through the main fuel gas supply tube 201 and in the event of a gas shutdown close the fourth shut-off valve 219 and the fifth shut-off valve 213, whereby the fuel gas between the fourth shut-off valve 219 and the fifth shut-off valve 213 is guided out of the fuel gas supply

DK 2019 70744 A1 14 system through the second blowout tube 215 and the fuel gas downstream of the fourth shut-off valve 219 is guided out of the fuel gas supply system through first blowout tube 211. As an extra safety mechanism, the first blowout tube 211 is further provided with a by-pass fuel gas tube 216 provided with a sixth shut-off valve 217, the sixth shut-off valve has an open state and a closed state, the fuel gas supply system being configured to keep the sixth shut-off valve 217 closed under normal operation an in the event of a gas shutdown open the sixth shut-off valve 217 whereby fuel gas may exit the fuel gas supply system through the first blowout tube 211 even if the — second shut-off valve 212 malfunctions.

Fig. 2c illustrates how fuel gas supply system may control the shut-off valves of Fig. 2b. Here each shut-off valve is provided an actuator for opening of closing the valve and a local control unit 221-226 configured to send control signal to the actuator. Each local control unit 221-226 is preferably further communicatively coupled to a central engine control unit configured to initiate a gas shutdown e.g. by transmitting control signals to the local control units 221-226. The gas pressure regulation valve 202 may comprise an actuator configured to modify the flow-resistance of the gas pressure regulation valve 202, whereby the gas pressure may be controlled.

The gas pressure regulation valve 202 may further comprise a control unit 205 and a first sensor 207, where the control unit 205 is communicatively connected to both the first sensor 207 and the actuator (not shown) and configured to control the actuator based on sensor data received from the first sensor (207). The control unit is preferably further communicatively connected to a central engine control unit. The first sensor may be configured to detect pressure, temperature, and / or flow downstream of the gas pressure regulation valve. Preferably the first sensor is configured to detect pressure and temperature downstream of the gas pressure regulation valve e.g. the first sensor comprises a pressure sensor and a temperature sensor.

Fig. 3a shows schematically a two-stroke internal combustion engines according to embodiments of the invention. Only a part of the fuel

DK 2019 70744 A1 15 gas supply system and the cylinders are schematically shown. The remaining parts of the engine may be similar to the engine shown in Fig. 1. The engine comprises six cylinders 301. The fuel gas supply system comprises for each cylinder 301 a fuel gas valve 305 arranged at least partly in the cylinder wall and configured to inject fuel gas into the cylinder 301 during the compression stroke enabling the fuel gas to mix with scavenge air and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited. The fuel gas supply system comprises a main fuel gas supply tube 316 for fluidly connecting the fuel gas valves 305 of the six cylinders with a fuel gas tank.

The main fuel gas supply tube 316 being provided with a gas pressure regulation valve 352 and a by-pass fuel gas tube 353 allowing the fuel gas to by-pass the gas pressure regulation valve 352. The gas pressure regulation valve 352 is controlled by a control unit 355. The fuel gas supply system has a first part being configured to be arranged in a no gas zone 320 and a — second part being configured to be arranged in a gas tolerated zone. Only the part of the fuel gas supply system being configured to be arranged in the no gas zone 320 is shown. The fuel gas supply system comprises for each cylinder 301 a fuel gas supply tube 306 fluidly connecting the main fuel gas supply tube 316 to the fuel gas valve 305. The by-pass gas tube 353 is provided with a shut-off valve 356 controlled by a control unit 356. The fuel gas supply system further comprises a purge system 390 391 392. The purge system comprises a reservoir 392 of an incombustible gas (e.g. nitrogen), a purge shut-off valve 390 having an open state and a closed state, and a purge control unit 391. The reservoir 392 is preferably pressurized preferably at a pressure above the fuel gas injection pressure. The purge shut-off valve 390 fluidly connects the reservoir 392 with a distal end of the main fuel gas supply tube 316. Under normal gas operation the purge shut-off valve 390 is kept closed preventing a flow of the incombustible gas to the main fuel gas supply tube 306. In the event of a gas shut-down, the fuel gas supply system controls: the purge control unit 391 to send a control signal to the purge shut-off valve 390 opening the purge shut-off valve

DK 2019 70744 A1 16 390, the control unit 356 to send a control signal to the shut-off valve 354 opening the shut-off valve, and the control unit 355 to send a control signal to the gas pressure regulation valve 352 opening the gas pressure regulation valve to its maximum position, whereby the incombustible gas enters the main fuel gas supply tube 316 an empties / purges the fuel gas in the part of the fuel gas supply system arranged in the no gas zone through the main fuel gas supply tube. The fuel gas supply system may preferably further control a shut-off valve to shut-off and prevent further flow of fuel gas from the fuel gas tank, and a another shut-off valve to open to allow the purged fuel gas to exit the fuel gas supply system through a blowout tube arranged outside the no gas zone 320. The fuel gas supply system preferably comprises a central control unit (not shown) communicatively coupled to the local control units 391 355 356 and configured to control the local control units 391 355 356.

Figs. 4ab illustrate how a metal block 400 having the gas pressure regulation valve and the by-pass fuel gas tube integrated may be manufactured according to an embodiment of the invention. The figures show schematically the metal block before the gas pressure regulation valve and the by-pass shut-off valve are arranged in the metal block 400, where Fig. 4a shows a top view and Fig. 4b shows a central cross-section taken along the line 410 shown in Fig. 4a. In order to manufacture the metal block 400, a first hole 401 is formed by drilling from the outside in the direction illustrated by the arrow 421. The first hole 401 has a first opening forming an inlet and a second opening forming an outlet. Next, a first part of the by-pass channel 408 is formed by drilling from the outside in the direction illustrated by the arrow 422. Then, a second part of the by-pass channel 404 is formed by drilling from the outside in the direction illustrated by the arrow 425. Next, a third part of the by-pass channel 406 is formed by drilling from the outside in the direction illustrated by the arrow 423. Next, to form the cavity 402 configured to receive a gas pressure regulation valve a large diameter drill is used to drill from the outside in the direction illustrated by the arrow 426.

DK 2019 70744 A1 17 Finally, to form the cavity 405 configured to receive a by-pass shut-off valve a large diameter drill is used to drill from the outside in the direction illustrated by the arrow 423. To seal the by-pass fuel gas tube a plug 430 is inserted into a part of the drill hole 403 and a by-pass shut-off valve (not shown) is inserted into the cavity 405. Optionally, a plug 431 is also inserted into a part of the drill hole 404.Finally, to seal the first hole 401 a gas pressure regulation valve (not shown) is inserted into the cavity 402. 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.

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 2019 70744 A1 18

1. A two-stroke uniflow scavenged crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system, 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 between bottom dead center and top dead center, the scavenge air system having a scavenge air inlet arranged at the bottom of the cylinder, wherein the two- stroke internal combustion engine is configured to inject into the least one cylinder a fuel gas via the fuel gas supply system, the fuel gas supply system comprising for the at least one cylinder one or more fuel gas valves arranged at least partly in the cylinder wall and configured to inject fuel gas into the cylinder during the compression stroke enabling the fuel gas to mix with scavenge air and allowing the mixture of scavenge air and fuel gas to be compressed before being ignited, wherein the fuel gas supply system comprises a main fuel gas supply tube for fluidly connecting the one or more fuel gas valves of the at least one cylinder with a fuel gas tank, the main fuel gas supply tube being provided with a gas pressure regulation valve, wherein the main fuel gas tube is further provided with a by-pass fuel gas tube allowing the fuel gas to by-pass the gas pressure regulation valve, a first part of the fuel gas supply system being configured to be arranged in a no gas zone and a second part of the fuel gas supply system being configured to be arranged in a gas tolerated zone, and wherein in the event of a gas shutdown the fuel gas supply system is configured to empty the fuel gas in the first part of the fuel gas supply system through the main fuel gas supply tube.

2. A two-stroke uniflow scavenged crosshead internal combustion engine according to claim 1, wherein the by-pass fuel gas tube is provided with a first shut-off valve having an open state and a closed state, the fuel gas supply system being configured to keep the first shut-off valve in the closed

DK 2019 70744 A1 19 state under normal operation to prevent flow of gas through the by-pass fuel gas tube and in the event of a gas shutdown open the first shut-off valve allowing fuel gas to flow through the by-pass fuel gas tube.

3. A two-stroke uniflow scavenged crosshead internal combustion engine according to any one of claims 1 to 2, wherein the fuel gas supply system further comprises a first blowout tube fluidly connected to the main fuel gas tube via a second shut-off valve having an open state and a closed state, the first blowout tube being fluidly connected to the main fuel gas tube upstream of the gas pressure regulation valve, the fuel gas supply system being configured to keep the second shut-off valve in the closed state under normal operation to prevent flow of gas through the first blowout tube and in the event of a gas shutdown open the second shut-off valve allowing fuel gas to exit the fuel gas supply system via the first blowout tube.

4. A two-stroke uniflow scavenged crosshead internal combustion engine according to claim 3, wherein the first blowout tube is configured to be arranged in a gas tolerated zone.

5. A two-stroke uniflow scavenged crosshead internal combustion engine according to claims 3 or 4, wherein the fuel gas supply system further comprises a second blowout tube fluidly connected to the main fuel gas tube via a third shut-off valve having an open state and a closed state, the second blowout tube being fluidly connected to the main fuel gas tube upstream of the first blow out tube, the fuel gas supply system being configured to keep the third shut-off valve in the closed state under normal operation to prevent flow of gas through the second blowout tube and in the event of a gas shutdown open the third shut-off valve allowing fuel gas to exit the fuel gas supply system via the second blowout tube.

DK 2019 70744 A1 20

6. A two-stroke uniflow scavenged crosshead internal combustion engine according to claim 5, wherein the main fuel gas supply tube is provided with a fourth shut-off valve arranged between the first blowout tube and the second blowout tube and a fifth shut-off valve arranged upstream of the second blowout tube, the fourth shut-off valve and the fifth shut-off valve have an open state and a closed state, the fuel gas supply system being configured to keep the fourth shut-off valve and the fifth shot-off valve in the open state under normal operation to allow fuel gas the flow through the main fuel gas supply tube and in the event of a gas shutdown close the fourth shut-off valve and the fifth shut-off valve.

7. A two-stroke uniflow scavenged crosshead internal combustion engine according to any one of claims 1 to 6, wherein the gas pressure regulation valve and the by-pass fuel gas tube is integrated into a metal block having an inlet connected with a first section of the main fuel gas supply tube and an outlet connected with a second section of the main fuel gas supply tube.

8. A two-stroke uniflow scavenged crosshead internal combustion engine according to claim 7, wherein the first and second section of the main fuel gas tube have an inner wall and an outer wall, the inlet of the metal block is configured to establish a fluid tight seal with both the outer wall and the inner wall of the first section of the main fuel gas supply tube, and the outlet of the metal block is configured to establish a fluid tight seal with both the outer wall and the inner wall of the second section of the main fuel gas supply tube.

9. A two-stroke uniflow scavenged crosshead internal combustion engine according to claim 8, wherein the metal block is obtained by the process comprising the steps of: e obtaining a solid metal block, e drilling in the solid metal block, from the outside, a first hole having a first opening forming the inlet and a second opening forming the outlet,

DK 2019 70744 A1 21 e drilling one or more times in the solid metal block from the outside a by-pass channel by-passing a central portion of the first hole thereby forming the by-pass fuel gas tube, e arranging a gas pressure regulation valve in the central portion of the first hole, and e optionally, arranging a shut-off valve in the by-pass fuel gas tube.

10. A two-stroke uniflow scavenged crosshead internal combustion engine according to claim 9, wherein the metal block further comprises a pressure sensor and a control unit, the control unit being communicatively connected to the pressure sensor and an actuator of the pressure regulation valve, the actuator being configured to modify a variable flow resistance in the pressure regulation valve, the control unit being configured to control the actuator based on sensor signals received from the pressure sensor.