A large turbocharged two-stroke dual-fuel uniflow crosshead internal combustion engine and a method for purging the fuel system of said engine.

Abstract

This invention provides a method for purging the fuel system of a large turbocharged two-stroke dual-fuel uniflow crosshead internal combustion engine. [Solution] The second fuel system comprises a second fuel tank, a second fuel supply line for supplying pressurized second fuel to a fuel valve, and a second fuel return line for returning pressurized second fuel from the fuel valve. The engine has a purge gas system for purging the second fuel from the fuel valve, the second fuel supply line, and the second fuel return line to a drain tank, wherein the method is characterized in that, after the purge is stopped, a space including at least a portion of the fuel valve and the second fuel supply and return line is isolated from the rest of the second fuel system by closing a plurality of valves, the internal pressure and temperature of the space are measured and used to determine whether the internal pressure of the space corresponds to the saturation pressure on the pressure / temperature saturation curve of the second fuel, and if the pressure in the space corresponds to the saturation pressure, the purge is continued.

Description

Technical Field

[0001] The present invention relates to a method for purging a fuel system of a large turbocharged two-stroke two-fuel uniflow crosshead internal combustion engine. However, the engine is at least one cylinder in a cylinder liner, a reciprocating piston disposed between the cylinder liner and a cylinder cover covering the cylinder, a combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner, a conventional fuel system for supplying a conventional fuel, and a second fuel system for supplying a second fuel such as ammonia or LPG, and the second fuel system includes a second fuel tank, a second fuel supply line for supplying pressurized second fuel to at least one fuel valve disposed in the cylinder cover or the cylinder liner, and a second fuel return line for returning the pressurized second fuel from the at least one fuel valve. The engine further has a purge gas system for purging the second fuel from the at least one fuel valve, the second fuel supply line, and the second fuel return line to a drain tank. Background of the Background

[0002] Large turbocharged two-stroke uniflow crosshead internal combustion engines are commonly used as prime movers for large ocean-going vessels such as container ships and power plants. This type of engine is very often operated with heavy oil or fuel oil such as diesel.

[0003] In recent years, there has been a demand to enable handling of another type of second fuel such as ammonia or LPG in large two-stroke diesel engines. An engine that can operate in both a fuel oil mode operating only with fuel oil and a second fuel mode operating with a second fuel and pilot fuel oil is often called a two-fuel engine.

[0004] Dual-fuel engines are required to operate on both conventional fuels, such as heavy oil or diesel, and the aforementioned second fuel, which may be more environmentally friendly. Therefore, a dedicated fuel supply and injection system is required for each type of fuel used. This requirement for two fuel supply and injection systems significantly increases the initial cost of engine manufacturing and enhances the engine's complexity and maintenance costs. However, some components, such as hydraulic pumps, can be used in conjunction with both the fuel supply and injection systems to provide hydraulic power to the fuel pump that pressurizes the fuel.

[0005] Thus, a dual-fuel engine comprises a conventional fuel system for the conventional fuel and a second fuel system for the second fuel. The conventional fuel system is well known in the art of this invention, so no further detailed description is provided. The second fuel system has elements installed on the deck of the vessel on which the engine is mounted, such as a second fuel tank. The second fuel system needs to connect the second fuel tank to the engine's fuel valve. The engine's fuel valve is usually installed inside the engine's cylinder cover or cylinder liner. During engine operation, this type of engine exhibits relatively large vibrations, so the fuel valve is constantly moving. However, the second fuel tank on the deck does not move. Therefore, the second fuel system must be able to absorb the movement of the fuel valve relative to the second fuel tank. This is difficult. If the second fuel tank and the fuel valve are connected in a straight line, the stresses generated in the second fuel supply line and the second fuel return line can become unmanageably large, and may cause leaks or ruptures, especially at the connections between sections of the fuel supply line and the return line. It is known in the art of this invention to provide elbows large enough to accommodate relative movement in a manner that does not create excessive stress on the pipes forming the supply and return lines. The larger the elbow, the greater the stress reduction. Since the fuel valve is located near the top of the engine and the second fuel tank is located on the deck, i.e., even higher than the fuel valve, the most effective way to create an elbow of sufficient size is to provide an elbow that extends widely downward from the fuel valve and the second fuel tank. However, such an elbow has a bottom section where two parts extending downward from the supply and return lines, respectively, merge. This poses a problem when purging the second fuel system with an inert gas. Purge is required, for example, when the second fuel system is not in use, especially before maintenance work on the second fuel system. The problem that arises at this time is that it is difficult to push out the liquid second fuel from the upward portion downstream of the bottom section of the supply line. This is because, as the inert gas passes through the layer of liquid second fuel in that upward portion, it may only foam without removing the liquid second fuel.Furthermore, liquid fuel II can also be trapped in other locations within the fuel II system. As a result, engine operators cannot be certain that the fuel II system is completely empty after purging, and maintenance work cannot be safely performed because fuel II may still be present.

[0006] WO2024 / 032900A1 describes a method for purging the engine's fuel system as mentioned at the beginning, but this method is not a reliable way to completely empty the fuel system. [Overview of the project]

[0007] The object of the present invention is to provide a method for purging the fuel system of a large turbocharged two-stroke twin-fuel uniflow crosshead internal combustion engine of the type described at the beginning, which at least significantly reduces the aforementioned problems relating to completely emptying the second fuel system.

[0008] The aforementioned and other issues are resolved by the features described in the independent claims. More specific implementations will become apparent from the dependent claims, specification, and drawings.

[0009] According to the first aspect, a method is provided for purging the fuel system of a large turbocharged two-stroke twin-fuel uniflow crosshead internal combustion engine. However, the aforementioned organization At least one cylinder in the cylinder liner, A reciprocating piston is disposed within the cylinder liner and the cylinder cover that covers the cylinder, Within the cylinder liner, a combustion chamber is formed between the reciprocating piston and the cylinder cover, A conventional fuel system that supplies conventional fuel, and a second fuel system that supplies a second fuel such as ammonia or LPG, The second fuel system comprises a second fuel tank, a second fuel supply line for supplying pressurized second fuel to at least one fuel valve located in the cylinder cover or the cylinder liner, and a second fuel return line for returning pressurized second fuel from the at least one fuel valve. The engine further includes the at least one fuel valve, the second fuel supply line, and a purge gas system for purging the second fuel from the second fuel return line to a drain tank. And the above method is At least one space, including at least a portion of the at least one fuel valve located in the cylinder cover or cylinder liner, and the second fuel supply line and return line, is isolated from the rest of the second fuel system by closing a plurality of valves after the purge is stopped. In order to determine whether the pressure inside the at least one space corresponds to the saturation pressure on the pressure / temperature saturation curve of each second fuel, the pressure and temperature inside the at least one space are measured and used. If the pressure in at least one of the spaces corresponds to the saturation pressure, the purging is continued.

[0010] Therefore, the operator can obtain clear information on whether the second fuel system is completely empty after a purge operation. When the pressure in the isolated space falls below the saturation pressure at the dominant temperature in that space (the saturation pressure according to the pressure / temperature saturation curve of the second fuel), it indicates that the space is completely empty and that further purging of the space is not necessary to enable maintenance work. This is because the pressure in the second fuel system rises until it reaches the saturation pressure while the remaining second fuel in the fuel system vaporizes in the isolated space. Therefore, it provides information on whether or not second fuel remains in the space after purging.

[0011] In one embodiment of the present invention, all fuel valves located in the cylinder cover or cylinder liner, and the second fuel supply line and return line are separated as a single space. However, it is also possible to divide the single space into at least two subspaces. In this way, the operator can know where in the at least two subspaces the remaining second fuel is located.

[0012] If it is indicated that residual second fuel is present in any of the at least two sub-spaces, it is preferable that the purging be continued only in that space.

[0013] In some embodiments, if the presence of residual second fuel is indicated, it would be preferable to measure the temperature at different locations within the at least one space in order to assess what the saturation pressure should be. This provides an additional indicator of whether the at least one space is empty and therefore safe to perform maintenance work on.

[0014] According to one embodiment of the first aspect, the purge gas system includes a purge gas supply unit.

[0015] According to a preferred embodiment of the first aspect, the purge gas is an inert gas, such as nitrogen.

[0016] According to the second aspect, a large turbocharged two-stroke, dual-fuel uniflow crosshead internal combustion engine is provided. This engine is, At least one cylinder in the cylinder liner, A reciprocating piston is disposed within the cylinder liner and the cylinder cover that covers the cylinder, Within the cylinder liner, a combustion chamber is formed between the reciprocating piston and the cylinder cover, A conventional fuel system that supplies conventional fuel, and a second fuel system that supplies a liquid second fuel such as ammonia or LPG, and has a second fuel system including a second fuel tank, a second fuel supply line for supplying pressurized second fuel to at least one fuel valve disposed in the cylinder cover or the cylinder liner, and a second fuel return line for returning the pressurized second fuel from the at least one fuel valve. The engine further has a purge gas system for purging the second fuel from the at least one fuel valve, the second fuel supply line, and the second fuel return line to a drain tank. And the engine has a plurality of valves for isolating at least one space including at least a part of the at least one fuel valve disposed in the cylinder cover or cylinder liner and the second fuel supply and return lines from the remainder of the second fuel system, means for measuring the pressure and temperature inside the at least one space, means for using the measured pressure and temperature to determine whether the pressure inside the at least one space corresponds to the saturation pressure on the pressure / temperature saturation curve of the respective second fuel, means for continuing the purge when the pressure in the at least one space corresponds to the saturation pressure. It is characterized by having the above.

Brief Description of the Drawings

[0017] Hereinafter, the present invention will be described in more detail with reference to the exemplary embodiments shown in the drawings. [Figure 1] FIG. shows an overview of a large two-stroke diesel engine according to an exemplary embodiment as seen from the front direction. [Figure 2] FIG. shows an overview of the large two-stroke engine of FIG. 1 as seen from the back direction. [Figure 3] FIG. schematically shows a first embodiment of the large two-stroke engine of FIGS. 1 and 2 together with its intake and exhaust systems. [Figure 4] FIG. is a schematic representation of the second fuel system of the large two-stroke engine of FIGS. 1 to 3. [Figure 5] It shows the saturation curve of ammonia with respect to temperature and pressure. Detailed Description

[0018] In the following detailed description, a large turbocharged two-stroke dual-fuel uniflow crosshead internal combustion engine of an exemplary embodiment is referred to, and an internal combustion engine, a ship equipped with the engine, a method of operating the engine, and a dual-fuel system for the engine are described. The illustrated large turbocharged two-stroke dual-fuel uniflow crosshead internal combustion engine is of a high-pressure type. That is, it is a compression ignition type in which fuel is injected at or near the top dead center of the piston.

[0019] The present disclosure provides a large two-stroke uniflow scavenged turbocharged internal combustion engine. FIGS. 1 and 2 depict a large low-speed turbocharged two-stroke internal combustion engine. This engine has a crankshaft 8 and a crosshead 9. FIG. 3 schematically represents a large low-speed turbocharged two-stroke diesel engine together with its intake system and exhaust system. This engine has six cylinders in series. A large low-speed turbocharged two-stroke internal combustion engine usually has 4 to 14 cylinders in series. These cylinders are carried by a cylinder frame 23. The cylinder frame 23 is carried by an engine frame 11. Also, such an engine can be used, for example, as a main engine of a ship or as a stationary type engine for driving a generator in a power plant. The total output of the engine can be in the range of, for example, 1,000 to 110,000 kW.

[0020] In the following examples, the engine is a two-stroke uniflow compression ignition type engine, a scavenging port 18 is provided in the lower region of each cylinder liner 1, and an exhaust valve is arranged at the center of the top of the cylinder liner 1. The cylinders of the engine are formed by the cylinder liners 1.

[0021] This engine is a dual-fuel engine capable of operating by switching between a conventional fuel (Fuel 1) and a different fuel (Fuel 2, e.g., ammonia or LPG). That is, it has an operating mode using Fuel 1 and another operating mode using Fuel 2. Fuel 1, being a conventional fuel, is typically fuel oil, such as marine diesel fuel or heavy oil.

[0022] During engine operation, scavenging air is introduced through the scavenging receiver 2 to the scavenging ports 18 of each cylinder 1. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1, compressing the scavenging air. Fuel is injected into the combustion chamber in the cylinder liner 1 at or near TDC through a plurality of high-pressure fuel valves 49 located in the cylinder cover 22. Combustion occurs following the fuel injection, generating exhaust gas. Each cylinder cover 22 is provided with two or more fuel valves 49. The fuel valves 49 are arranged in the cylinder cover 22 around the exhaust valve 4 located in the center of the cylinder cover 22. The fuel valves 49 receive fuel from the fuel supply system 30.

[0023] When the exhaust valve 4 opens, the exhaust gas flows through the exhaust ducts provided in each cylinder to the exhaust receiver 3, and then through the first exhaust pipe 19 to the turbine 6 of the turbocharger 5. From there, the exhaust gas is released into the atmosphere through the second exhaust pipe 25 and the exhaust outlet 21.

[0024] The turbine 6 drives the compressor 7 via a shaft. The compressor 9 is supplied with outside air through the air intake 12. The compressor 7 sends the compressed scavenging air to the scavenging pipe 13, which is connected to the scavenging receiver 2. The scavenging air in the scavenging pipe 13 passes through the intercooler 14 to cool the scavenging air.

[0025] The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging airflow when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging tank 2, i.e., when the engine is under low or partial load. When the engine is under high load, the compressor 7 of the turbocharger can supply sufficiently compressed scavenging air, so the auxiliary blower 16 is bypassed by a check valve 15 and the electric motor 17 is stopped.

[0026] For each engine cycle, the precise amount of fuel to be administered is injected into the cylinder 1 through the fuel valve 49. In some embodiments, the electronic control unit 50 is configured to calculate the engine load as a function of the amount of fuel administered.

[0027] The engine's fuel system has a first fuel system for the first fuel, which is a conventional fuel such as fuel oil. The first fuel system is well known, so no further details will be provided.

[0028] Figure 4 is a schematic representation of the second fuel system 30 of a vessel equipped with a large two-stroke engine. The second fuel system 30 is divided into two main sections: a deck section and an engine room section.

[0029] The second fuel system 30 includes a second fuel tank 31 in the deck section for storing the second fuel. The second fuel tank 31 is connected to a fuel supply line 32. A fuel return line 36 is connected to a drain tank 52, from which the second fuel may be returned to the second fuel tank 31 by means of (not shown). These lines 32 and 36 extend from the deck section to the engine room section.

[0030] In the engine room section, the fuel supply line 32 is composed of multiple sections, including a first supply line section 32a having a portion running in the vertical direction, a lower supply line section 32b, and a second supply line section 32c having a portion running in the vertical direction. Similarly, the fuel return line 36 may be composed of multiple sections, including a first return line section 36a, a lower return line section 36b, and a second return line section 36c. The fuel supply line 32 leads to at least one fuel valve 49 located in the cylinder cover 22. The fuel valve 49 is connected to the fuel supply line 32 via a fuel valve supply line 38 including a first control valve 40, and to the fuel return line 36 via a fuel valve return line 39 including a second control valve 41.

[0031] The illustrated system further includes a first bypass valve 34 connecting the downstream supply line section 32b to the fuel return line 36. A second bypass valve 35 can connect a portion of the fuel supply line 32 downstream of the second supply line section 32c to the fuel return line 36.

[0032] The fuel supply line 32 has a first supply line section 32a having a portion running in the vertical direction, and a second supply line section 32c having a portion running in the vertical direction. Furthermore, the downstream supply line section 32b of the fuel supply line is provided between the first supply line section 32a and the second supply line section 32b. The first supply line section 32a is located upstream of the downstream supply line section 32b, and the second supply line section 32c is located downstream of the downstream supply line section 32b. The fuel return line 36 has a first return line section 36a having a portion running in the vertical direction, and a second return line section 37c having a portion running in the vertical direction. Furthermore, the lowest return line section 36b of the fuel supply line 36 is provided between the first return line section 36a and the second return line section 36c. The first return line section 36a is located upstream of the lowest return line section 36b, and the second return line section 36c is located downstream of the lowest return line section 36b.

[0033] The purge gas system has an inert gas supply device 61 connected to the fuel supply line 32 through an inert gas supply line 37. The inert gas supply line 37 preferably includes a valve 37a or similar element for controlling the flow of purge gas to the fuel supply line 32. The purge gas is, for example, nitrogen. The purge gas is used to push the second fuel out of the system during purging. This is necessary, for example, when the engine is running on the first fuel and the second fuel system 30 is not in use. It is also particularly necessary when maintenance needs to be performed on the second fuel system 30.

[0034] The drain tank 52 is located higher than the lowest supply line section 32b. The drain tank 52 is used to recover the second fuel during purging operations. The mixture of the purged second fuel and purge gas is processed in a system (not shown), and the second fuel may be returned to the second fuel tank 31.

[0035] The system may also include a liquid sensor 43, which is configured to detect the presence of liquid second fuel in the bottom supply line section 32b or the bottom return line section 36b.

[0036] Additional components include a working fluid control valve 45, a one-way valve 46, a working fluid supply line 47, and a working fluid return line 48, which are part of the fuel valve actuation system. The fuel valve actuation system is configured to actuate the fuel valve 49 in a timely manner to perform fuel injection events with a precise dosage of second fuel.

[0037] This configuration of the second fuel system 30 allows for efficient supply of the second fuel during normal operation and effective purging of the system when necessary. The vertically running portions of the supply line section and return line section help to accommodate relative movement between the engine and deck components due to engine vibration. Meanwhile, if bypass valves are implemented, they facilitate the complete discharge of the second fuel during purging operations. All or some of the valves 34, 35, 40, 41 of the second fuel system, as well as the valves 32d, 37a, 36d of the fuel supply line 32, the inert gas supply line 37, and the fuel return line 36, can be controlled by the electronic control unit 50.

[0038] Although the aforementioned purge gas system was supposed to completely discharge all of the second fuel from the fuel valves, second fuel supply line, and return line of the second fuel system, some remaining second fuel may still remain in the second fuel system.

[0039] Therefore, after purging is stopped, the second fuel valve 49 and the second fuel supply and return lines 32,36 are isolated from the rest of the second fuel system by closing valves 32d,37a,36d in accordance with the present invention. Next, immediately after valves 32a,37a,36a are closed, the pressure and temperature inside the at least one space are measured by at least one pressure sensor 51 and temperature sensor 52. In the embodiment of Figure 4, multiple pressure sensors 51 are used, each positioned to measure the pressure inside the second fuel valve 49, the second fuel supply line 32, and the second fuel return line 36. The pressure and temperature measurements are used to determine whether the pressure inside the at least one space corresponds to the saturation pressure on the pressure / temperature saturation curve for each of the second fuels. See the ammonia pressure / temperature saturation curve in Figure 5. If the pressure inside the at least one space corresponds to the saturation pressure shown on the pressure / temperature saturation curve at the temperature inside, purging is continued. This indicates that the second fuel is still present in the second fuel valve 49 and the second fuel supply / return lines 32, 36, and as this remaining second fuel evaporates, the pressure inside the second fuel valve 49 and the second fuel supply / return lines 32, 36 rises to the saturation pressure of the second fuel at that temperature.

[0040] According to the present invention, this procedure is continued until the pressure in the space including the second fuel valve 49 and the second fuel supply and return lines 32, 36 falls below the saturation pressure. When the pressure falls below the saturation pressure, it indicates that the space is completely empty and that further purging of the space is unnecessary to enable maintenance work.

[0041] The space containing all the fuel valves 49 and the second fuel supply and return lines 32, 36 can be divided into, for example, three sub-spaces by further closing valves 35, 40, 41. In this way, the system is divided into a space containing the fuel supply line 32, a space containing the fuel valve supply line 38, fuel valve 49 and fuel valve return line 39, and a space containing the fuel return line 36. In this way, the operator will have information on where in the three sub-spaces the remaining second fuel is located.

Claims

1. A method for purging the fuel system of a large turbocharged two-stroke dual-fuel uniflow crosshead internal combustion engine, However, the aforementioned organization At least one cylinder in the cylinder liner, A reciprocating piston is disposed within the cylinder liner and the cylinder cover that covers the cylinder, Within the cylinder liner, a combustion chamber is formed between the reciprocating piston and the cylinder cover, A conventional fuel system that supplies conventional fuel, and a second fuel system that supplies a liquid second fuel such as ammonia or LPG, The second fuel system comprises a second fuel tank, a second fuel supply line for supplying pressurized second fuel to at least one fuel valve located in the cylinder cover or the cylinder liner, and a second fuel return line for returning pressurized second fuel from the at least one fuel valve. The engine further includes the at least one fuel valve, the second fuel supply line, and a purge gas system for purging the second fuel from the second fuel return line to a drain tank. And the above method is At least one space, including at least a portion of the at least one fuel valve located in the cylinder cover or cylinder liner, and the second fuel supply line and return line, is isolated from the rest of the second fuel system by closing a plurality of valves after the purge is stopped. In order to determine whether the pressure inside the at least one space corresponds to the saturation pressure on the pressure / temperature saturation curve of each second fuel, the pressure and temperature inside the at least one space are measured and used. If the pressure in at least one of the spaces corresponds to the saturation pressure, the purging is continued. A method characterized by the following features.

2. The method according to claim 1, characterized in that the at least one space is divided into at least two subspaces.

3. The method according to claim 2, characterized in that if it is indicated that residual second fuel is present in any of the at least two subspaces, the purging is continued only in that space.

4. The method according to claim 1, characterized in that, if the presence of a remaining second fuel is indicated, the temperature is measured at different locations in the at least one space in order to evaluate what the saturation pressure should be.

5. The method according to claim 1, characterized in that the purge gas system has a purge gas supply device.

6. The method according to claim 5, characterized in that the purge gas is an inert gas such as nitrogen.

7. A large turbocharged two-stroke dual-fuel uniflow crosshead internal combustion engine, wherein the engine is At least one cylinder in the cylinder liner, A reciprocating piston is disposed within the cylinder liner and the cylinder cover that covers the cylinder, Within the cylinder liner, a combustion chamber is formed between the reciprocating piston and the cylinder cover, A conventional fuel system that supplies conventional fuel, and a second fuel system that supplies a liquid second fuel such as ammonia or LPG, The second fuel system comprises a second fuel tank, a second fuel supply line for supplying pressurized second fuel to at least one fuel valve located in the cylinder cover or the cylinder liner, and a second fuel return line for returning pressurized second fuel from the at least one fuel valve. The engine further includes the at least one fuel valve, the second fuel supply line, and a purge gas system for purging the second fuel from the second fuel return line to a drain tank. And the aforementioned organization, A plurality of valves for isolating at least one space, including at least a portion of the at least one fuel valve located in the cylinder cover or cylinder liner, and the second fuel supply line and return line, from the rest of the second fuel system, Means for measuring the pressure and temperature inside the at least one space, Means for using the measured pressure and temperature to determine whether the pressure inside the at least one space corresponds to the saturation pressure on the pressure / temperature saturation curve of each second fuel, If the pressure in at least one of the spaces corresponds to the saturation pressure, means for continuing the purging, An organization characterized by having the following features.

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