Long distance transmission high pressure host LNG fuel supply system and control method

Abstract

The application discloses a kind of long-distance transmission high-pressure main machine LNG fuel supply system and control method, comprising: fuel tank, long-distance gas supply pipe and high-pressure main machine;The fuel tank and high-pressure main machine are connected by long-distance gas supply pipe, and the both ends of the long-distance gas supply pipe are provided with ESD main valve and auxiliary main valve;Close the ESD main valve and auxiliary main valve, can make the gas in the long-distance gas supply pipe pressure storage.High-pressure main machine is converted from fuel mode to natural gas mode operation, if first operation fails, close ESD main valve and auxiliary main valve, so that long-distance gas supply pipe can temporarily pressure storage gas, in subsequent second operation, since the long-distance gas supply pipe of stored gas does not need to reestablish pressure, can save the time of establishing pressure.This makes the conversion operation from fuel mode to natural gas mode can be quickly completed, significantly improves the speed and success rate of mode switching.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LNG fuel supply, in particular to a long-distance transmission high-pressure main engine LNG fuel supply system and a control method. BACKGROUND

[0002] In the design of large container ships, the double island layout is widely used, in which the main engine is usually installed at the stern, and the fuel tank is located near the front island, ensuring that the fuel tank is kept a certain distance from the main engine, usually more than 100 meters. Large ships usually use high-pressure main engines, for example, the ME-GI main engine (dual fuel diesel engine) widely recognized by the market, whose gas supply design pressure is 300-400 barG.

[0003] The double island layout poses a series of challenges to the high-pressure gas supply system. The pipeline distance from the gas supply equipment to the main engine user is long, and the gas supply pressure needs to be maintained at a high level. Before the gas is supplied to the main engine, sufficient pressure must be established in the pipeline. If the time to establish the gas supply pressure exceeds the main engine start-up setting time (usually 5-10 seconds), the main engine will fail to switch from fuel mode to natural gas mode, triggering a nitrogen purge program to clean all pipelines downstream of the main valve, and then the main engine can be restarted. Each time the main engine fails to start, the gas supply pressure must be re-established, with a high failure rate. Each time the main engine is shut down, a large amount of gas in the long-distance gas supply pipeline will be purged, which not only wastes gas resources but also causes serious environmental pollution. SUMMARY

[0004] The present application provides a long-distance transmission high-pressure main engine LNG fuel supply system and a control method to overcome the above problems.

[0005] To achieve the above purpose, the technical solution of the present application is:

[0006] A long-distance transmission high-pressure main engine LNG fuel supply system, comprising: a fuel tank, a long-distance gas supply pipe and a high-pressure main engine;

[0007] The fuel tank and the high-pressure main engine are connected by the long-distance gas supply pipe, and the long-distance gas supply pipe is provided with an ESD main valve and an auxiliary main valve at both ends;

[0008] Closing the ESD main valve and the auxiliary main valve can store the gas in the long-distance gas supply pipe.

[0009] Furthermore, the fuel tank is equipped with a fuel supply pump. The outlet of the fuel supply pump is connected to the inlet of the high-pressure pump via a low-pressure LNG fuel pipe. The outlet of the high-pressure pump is connected to the inlet of the high-pressure evaporator via a high-pressure LNG fuel pipe. The outlet of the high-pressure evaporator is connected to the inlet of the buffer tank via a pipeline. The outlet of the buffer tank is connected to the inlet of the ESD main valve of the gas equipment via a high-pressure NG gas pipe. The outlet of the ESD main valve is connected to the inlet of the auxiliary main valve via a long-distance gas supply pipe. The outlet of the auxiliary main valve is connected to the inlet of the gas valve assembly unit via a pipeline. The outlet of the gas valve assembly unit is connected to the inlet of the high-pressure main engine via a pipeline.

[0010] Furthermore, the high-voltage main unit is located inside the engine room, and the fuel tank is located on the main deck away from the engine room or in a fuel tank location. A GVT room and a fuel preparation room are provided between the fuel tank and the engine room. The GVT room is close to the engine room, and the fuel preparation room is close to the fuel tank.

[0011] The gas valve assembly unit is located in the GVT room, which is equipped with a ventilation system. The high-pressure pump, high-pressure evaporator, and buffer tank are located in the fuel preparation room, which is also equipped with a ventilation system.

[0012] Furthermore, it also includes a first nitrogen purging line and a first venting line;

[0013] The outlet of the first nitrogen purging pipeline is connected to the end of the long-distance gas supply pipeline near the ESD main valve. The first nitrogen purging pipeline is equipped with a first purging control valve. The inlet of the first vent pipeline is connected to the end of the long-distance gas supply pipeline near the auxiliary main valve. The first vent pipeline is equipped with a first vent control valve.

[0014] Furthermore, the long-distance gas supply pipe is provided with several expansion bends.

[0015] Furthermore, the return port of the high-pressure pump is connected to the fuel tank via a return pipe;

[0016] It also includes a pressure relief pipe, the two ends of which are respectively connected to a long-distance gas supply pipe and a return pipe, and a pressure relief valve is provided on the pressure relief pipe.

[0017] Furthermore, the outlet of the gas valve assembly unit is connected to the inlet of the high-pressure main unit via a double-walled pipe.

[0018] Furthermore, the ventilation systems of both the GVT room and the fuel preparation room are redundantly configured.

[0019] Furthermore, the long-distance gas supply pipe is equipped with a pipe heat tracing device.

[0020] The present invention also discloses a control method for a long-distance transmission high-pressure host LNG fuel supply system. Using the aforementioned long-distance transmission high-pressure host LNG fuel supply system, the high-pressure host switches from fuel oil mode to natural gas mode. The fuel tank supplies gas to the high-pressure host through a long-distance gas supply pipe. When the time to establish gas supply pressure exceeds the host start-up set time, the ESD main valve and auxiliary main valve are closed to keep the gas in the long-distance gas supply pipe under pressure and store it. The gas pressure storage time is less than the process requirement time.

[0021] The high-pressure main unit switches back from fuel oil mode to natural gas mode, opens the ESD main valve and auxiliary main valve, and the fuel tank supplies gas to the high-pressure main unit again through a long-distance gas supply pipe.

[0022] Beneficial effects:

[0023] This invention provides a long-distance high-pressure LNG fuel supply system and control method. By installing an ESD main valve and an auxiliary main valve at both ends of the long-distance gas supply pipe, when the high-pressure host switches from fuel oil mode to natural gas mode, if the initial operation fails, the ESD main valve and auxiliary main valve are closed. This allows the long-distance gas supply pipe to temporarily maintain pressure and store gas. In the subsequent second operation, since the long-distance gas supply pipe is already pressurized, there is no need to rebuild the pressure. Only the pipeline before the ESD main valve inlet and the pipeline after the auxiliary main valve outlet need to be filled and pressurized to the working pressure (approximately 300 to 400 bar). Therefore, the entire fuel supply system can quickly reach the required gas supply pressure, saving pressure build-up time. This enables rapid completion of the switch from fuel oil mode to natural gas mode, significantly improving the speed and success rate of mode switching. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a long-distance transmission high-pressure main engine LNG fuel supply system disclosed in this invention.

[0026] In the picture:

[0027] 1. Fuel tank;

[0028] 21. First fuel supply pump; 22. Second fuel supply pump;

[0029] 31. First high-pressure pump; 32. Second high-pressure pump;

[0030] 4. High-pressure evaporator;

[0031] 5. Buffer tank;

[0032] 6. Gas valve assembly unit;

[0033] 7. High-voltage main unit;

[0034] 81. First exhaust fan; 82. Second exhaust fan;

[0035] 91. Third-row fan; 92. Fourth-row fan;

[0036] L1, Low-pressure LNG fuel pipe; L2, High-pressure LNG fuel pipe; L3, Return pipe; L4, High-pressure LNG gas pipe; L5, Long-distance gas supply pipe; L6, Double-walled pipe; L7, First nitrogen purging line; L8, First venting line; L9, Second venting line; L10, Third venting line; L11, Second nitrogen purging line; L12, Pressure relief pipe; L13, Expansion bend; L14, Third nitrogen purging line;

[0037] V11, First valve; V12, Second valve; V13, Third valve; V14, ESD main valve; V15, Auxiliary main valve; V16, Main valve; V21, First purge control valve; V22, First vent control valve; V23, Second purge control valve; V24, Second vent control valve; V25, Third vent control valve; V26, Third vent control valve; V31, Pressure relief valve;

[0038] A. Engine room; B. Fuel preparation room; C. GVT room. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides a long-distance transmission system for supplying LNG fuel to a high-pressure main engine, such as... Figure 1 As shown, it includes: fuel tank 1, long-distance gas supply pipe L5 and high-pressure main unit 7;

[0042] The fuel tank 1 and the high-pressure main unit 7 are connected by a long-distance gas supply pipe L5, and the long-distance gas supply pipe L5 is equipped with an ESD main valve V14 and an auxiliary main valve V15 at both ends.

[0043] Closing the ESD main valve V14 and auxiliary main valve V15 allows for pressurized storage of gas within the long-distance gas supply pipe L5. A pipe heat tracing device (heat tracing tape / heat tracing pipe) can be installed around the outer periphery of the long-distance gas supply pipe L5 to prevent the gas within L5 from cooling down and failing to meet the main unit's supply requirements.

[0044] This embodiment provides a long-distance high-pressure LNG fuel supply system. By installing an ESD main valve V14 and an auxiliary main valve V15 at both ends of the long-distance gas supply pipe L5, when the high-pressure host 7 switches from fuel oil mode to natural gas mode, if the initial operation fails, the ESD main valve V14 and auxiliary main valve V15 are closed. This allows the long-distance gas supply pipe L5 to temporarily maintain pressure and store gas. In the subsequent second operation, since the long-distance gas supply pipe L5 is already pressurized, there is no need to rebuild the pressure. Only the pipeline before the inlet of the ESD main valve V14 and the pipeline after the outlet of the auxiliary main valve V15 need to be filled and pressurized to the working pressure (approximately 300 to 400 bar). Therefore, the entire fuel supply system can quickly reach the required gas supply pressure, saving pressure build-up time. This allows for a rapid transition from fuel oil mode to natural gas mode, significantly improving the speed and success rate of mode switching.

[0045] Specifically, the fuel tank 1 is equipped with a fuel supply pump. The outlet of the fuel supply pump is connected to the inlet of the high-pressure pump via a low-pressure LNG fuel pipe L1. The outlet of the high-pressure pump is connected to the inlet of the high-pressure evaporator 4 via a high-pressure LNG fuel pipe L2. The outlet of the high-pressure evaporator 4 is connected to the inlet of the buffer tank 5 via a pipeline. The outlet of the buffer tank 5 is connected to the inlet of the ESD main valve V14 of the gas equipment via a high-pressure NG gas pipe L4. The outlet of the ESD main valve V14 is connected to the inlet of the auxiliary main valve V15 via a long-distance gas supply pipe L5. The outlet of the auxiliary main valve V15 is connected to the inlet of the gas valve assembly unit 6 via a pipeline. The outlet of the gas valve assembly unit 6 is connected to the inlet of the high-pressure main unit 7 via a pipeline.

[0046] In this embodiment, the fuel supply pump and the high-pressure pump are both one standby and one in use. The fuel supply pump includes a first fuel supply pump 21 and a second fuel supply pump 22 connected in parallel (a first valve V11 and a second valve V12 are provided on the low-pressure LNG fuel pipe L1, and the first valve V11 and the second valve V12 are used to control the opening and closing of the low-pressure LNG fuel pipe L1). The high-pressure pump includes a first high-pressure pump 31 and a second high-pressure pump 32 connected in parallel.

[0047] The fuel supply pump supplies low-pressure LNG fuel to the high-pressure pump through the low-pressure LNG fuel pipe L1. The low-pressure LNG fuel is sent to the high-pressure evaporator 4 through the high-pressure LNG fuel pipe L2. The high-pressure evaporator 4 evaporates the LNG into gaseous NG. The gaseous NG enters the high-pressure NG gas pipe L4 through the buffer tank 5, and then is delivered to the high-pressure main unit 7 through the long-distance gas supply pipe L5 and the gas valve group unit 6.

[0048] Specifically, the high-pressure main engine 7 is located in the engine room A, and the fuel tank 1 is located on the main deck away from the engine room A or in the fuel tank area (the specific distance depends on the size of the ship, and the distance between the high-pressure main engine 7 and the fuel tank 1 should usually be greater than 100 meters). A GVT room C and a fuel preparation room B are provided between the fuel tank 1 and the engine room A. The GVT room C is close to the engine room A, and the fuel preparation room B is close to the fuel tank 1.

[0049] The gas valve assembly unit 6 is located in the GVT room C, which is equipped with a ventilation system. The high-pressure pump, high-pressure evaporator 4, buffer tank 5, and valves and pipelines connected to the high-pressure pump, high-pressure evaporator 4, and buffer tank 5 are all located in the fuel preparation room B, which is equipped with a ventilation system.

[0050] Specifically, it also includes a first nitrogen purging line L7 and a first venting line L8;

[0051] The outlet of the first nitrogen purging line L7 is connected to one end of the long-distance gas supply line L5 near the ESD main valve V14. The first nitrogen purging line L7 is equipped with a first purging control valve V21. The inlet of the first vent line L8 is connected to one end of the long-distance gas supply line L5 near the auxiliary main valve V15. The first vent line L8 is equipped with a first vent control valve V22.

[0052] The first nitrogen purging line L7 and the first venting line L8 are used only for purging during maintenance operations. The gas inside the long-distance gas supply line L5 is not purged when the high-pressure main unit 7 is shut down or the fuel supply system is in emergency shutdown (ESD). The auxiliary main valve V15 and the gas equipment ESD main valve V14 seal the high-pressure gas (NG) in the long-distance gas supply line L5, maintaining the working pressure when the high-pressure main unit 7 is shut down or the fuel supply system is in emergency shutdown (ESD). This can effectively reduce gas waste caused by purging, reduce greenhouse gas emissions, and protect the environment.

[0053] Specifically, the long-distance gas supply pipe L5 is provided with several expansion bends L13. The long-distance gas supply pipe L1 is arranged in the main hull area. All pipes on the long-distance gas supply pipe L1 are butt welded to avoid the use of flange connections, thereby reducing the risk of leakage. Multiple expansion bends L13 are provided to improve the flexibility of the pipe and meet stress requirements.

[0054] Specifically, the return port of the high-pressure pump is connected to the fuel tank 1 through the return pipe L3, which can return excess LNG in the high-pressure pump to the fuel tank 1. The return pipe L3 is equipped with a third valve V13 for controlling the opening and closing of the return pipe L3.

[0055] It also includes a pressure relief pipe L12, with its two ends connected to a long-distance gas supply pipe L5 and a return pipe L3, respectively. A pressure relief valve V31 is installed on the pressure relief pipe L12. When the pressure in the long-distance gas supply pipe L5 exceeds the set pressure value of the pressure relief valve V31, the pressure relief valve V31 automatically releases gas. A pressure sensor should be installed on the long-distance gas supply pipe L5 to monitor the pipeline pressure and ensure pipeline safety.

[0056] The first vent control valve V22 is a manual valve, and the pressure relief valve V31 is an automatic valve. They are used to manually and automatically control the pressure of the gas in the remote gas supply pipe L5 to ensure system safety.

[0057] Specifically, the outlet of the gas valve assembly unit 6 is connected to the inlet of the high-pressure host 7 via a double-walled pipe L6. The double-walled pipe L6 should be pressure monitored according to design requirements before it can be used.

[0058] When the long-distance gas supply pipeline L5 is laid on an open deck, a single-wall pipe can be used; if it is laid in a closed space such as a pipe channel, a double-wall pipe must be used.

[0059] Specifically, the ventilation systems of GVT room C and fuel preparation room B are redundant, with one in standby and the other in use. Fuel preparation room B and GVT room C are designated as hazardous areas, requiring guaranteed ventilation and increased inspection frequency. Cabin A is designated as a safe area.

[0060] Specifically, the ventilation system of fuel preparation room B includes a natural air intake hood and two sets of exhaust fans (first exhaust fan 81 and second exhaust fan 82, with one set of exhaust fans on standby) to ensure good ventilation in the room and no dead corners. A combustible gas alarm is installed in the room.

[0061] The ventilation system of GVT room C includes a natural air intake hood and two sets of exhaust fans (the third exhaust fan 91 and the fourth exhaust fan 92, with one set of exhaust fans as a backup) to ensure good ventilation in the room and no dead corners. A combustible gas alarm is installed in the room.

[0062] Specifically, the fuel supply pump is selected from deep well pumps or submersible pumps.

[0063] Specifically, the gas valve assembly unit 6 (GVT unit) has ESD, nitrogen purging, and venting functions. The gas valve assembly unit 6 and the high-pressure main unit 7 are complementary products, provided by the manufacturer of the high-pressure main unit 7. The gas valve assembly unit 6 is prior art, and its overall structure and logic will not be described in detail here. To facilitate the explanation of the working process of this application, only a brief description of part of the structure of the gas valve assembly unit 6 is provided below.

[0064] The gas valve assembly unit 6 includes a main valve V16, a second nitrogen purging line L11, a second vent line L9, and a third vent line L10. The inlet of the main valve V16 is connected to the outlet of the auxiliary main valve V15, and the outlet of the main valve V16 is connected to the inlet of the high-pressure main unit 7.

[0065] The outlet of the second nitrogen purging line L11 is connected to the end of the line where the main valve V16 is installed, which is close to the auxiliary main valve V15. The second nitrogen purging line L11 is provided with a second purging control valve V23.

[0066] The inlet of the third vent pipe L10 is connected to the end of the pipe where the main valve V16 is installed, which is close to the high-pressure host 7. The third vent pipe L10 is equipped with a third vent control valve V25.

[0067] The inlet of the second venting pipe L9 is connected to the pipe on which the main valve V16 is installed. The second venting pipe L9 is located between the second nitrogen purging pipe L11 and the third venting pipe L10. The second venting pipe L9 is equipped with a second venting control valve V24.

[0068] When the high-pressure main unit 7 is shut down / the fuel supply system experiences an emergency shutdown (ESD), the gas supply pipeline needs to be purged with nitrogen. If no overall maintenance of the fuel supply system is performed, the remote gas supply pipeline L5 is not purged. The main valve V16, auxiliary main valve V15, and the gas equipment ESD main valve V14 are shut off in an emergency. The second purging control valve V23 on the second nitrogen purging pipeline L11 and the second venting control valve V24 on the second venting pipeline L9 are opened, allowing the gas in the gas valve assembly unit 6 to pass through the nitrogen discharged from the second nitrogen purging pipeline L11 and the second venting control valve V24. Pipeline L9 is purged to the venting mast. The third purging control valve V26 on the third nitrogen purging pipeline L14 and the third venting control valve V25 on the third venting pipeline L10 are opened, allowing the gas in the high-pressure main unit 7 to be purged to the venting mast via the nitrogen discharged through the third nitrogen purging pipeline L14 and the third venting pipeline L10. When purging the pipeline, since only the pipeline from the high-pressure main unit 7 to the main valve V16 and the pipeline from the main valve V16 to the auxiliary main valve V15 are purged, the purging efficiency can be greatly improved, saving the waste of fuel in the pipeline during purging. At the same time, the pollution of the gas discharged during purging to the environment is reduced.

[0069] Example 2

[0070] This embodiment provides a control method for a long-distance transmission high-pressure LNG fuel supply system. Using the long-distance transmission high-pressure LNG fuel supply system described in Embodiment 2, the high-pressure main unit 7 switches from fuel oil mode to natural gas mode. The fuel tank 1 supplies gas to the high-pressure main unit 7 via a long-distance gas supply pipe L5. When the time to establish gas supply pressure exceeds the main unit startup set time, the ESD main valve V14 and auxiliary main valve V15 are closed, allowing the gas in the long-distance gas supply pipe L5 to be pressurized and stored. The gas pressure storage time is less than the process requirement time, which can be obtained through testing and specifically determined based on the pressure holding time of the long-distance gas supply pipe L5. Under normal circumstances, the process requirement time should be controlled within 10 minutes. However, if complex situations arise during the maintenance of the high-pressure main unit 7, necessitating an extension of the main unit 7's downtime, the pressure holding time can be extended until the end of the maintenance. At this time, the temperature of the gas in the long-distance gas supply pipe L5 should be monitored (a temperature sensor is installed on the long-distance gas supply pipe L5). If the temperature is too low, the pipeline heating device will heat the long-distance gas supply pipe L5 to prevent the gas from failing to meet the gas supply requirements of the main unit due to the drop in temperature.

[0071] The high-pressure main unit 7 switches from fuel oil mode to natural gas mode again, opening the ESD main valve V14 and auxiliary main valve V15. The fuel tank 1 then supplies gas to the high-pressure main unit 7 again through the long-distance gas supply pipe L5.

[0072] When the high-pressure main unit 7 switches from fuel oil mode to natural gas mode, it first establishes pressure in the remote gas supply pipe L5 until it meets the working pressure requirements of the high-pressure main unit 7. Since the remote gas supply pipe L5 is not purged when the high-pressure main unit 7 is shut down or the fuel supply system is in emergency shutdown (ESD), the pressure established in the remote gas supply pipe L5 can be maintained. When the high-pressure main unit 7 switches modes later, it does not need to spend a long time charging to ensure that the entire fuel supply system establishes pressure, which can achieve a faster conversion from fuel oil to natural gas and improve the conversion speed and success rate.

[0073] When the high-pressure main unit 7 is shut down / the fuel supply system experiences an emergency shutdown (ESD), the long-distance gas supply pipe L5 is not purged; purging is only performed during maintenance operations. This application, by adopting optimized pipeline design and valve control logic, significantly improves the operational performance of the fuel supply system and achieves energy conservation, emission reduction, and environmental benefits by effectively reducing greenhouse gas emissions.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A long-distance transmission high-pressure main engine LNG fuel supply system, characterized in that, include: Fuel tank (1), long-distance gas supply pipe (L5) and high-pressure main unit (7); The fuel tank (1) and the high-pressure main unit (7) are connected by a long-distance gas supply pipe (L5), and the long-distance gas supply pipe (L5) is equipped with an ESD main valve (V14) and an auxiliary main valve (V15) at both ends. Closing the ESD main valve (V14) and auxiliary main valve (V15) allows the gas in the remote gas supply pipe (L5) to be pressurized and stored. It also includes a first nitrogen purging line (L7) and a first venting line (L8); the outlet of the first nitrogen purging line (L7) is connected to the end of the remote gas supply pipe (L5) near the ESD main valve (V14), and a first purging control valve (V21) is provided on the first nitrogen purging line (L7); the inlet of the first venting line (L8) is connected to the end of the remote gas supply pipe (L5) near the auxiliary main valve (V15), and a first venting control valve (V22) is provided on the first venting line (L8); When the high-pressure host (7) stops or the fuel supply system shuts down in an emergency, the ESD main valve (V14), auxiliary main valve (V15), first purge control valve (V21) and first vent control valve (V22) are closed to keep the remote gas supply pipe (L5) in a sealed state. When the fuel supply system requires maintenance, the first purge control valve (V21) and the first vent control valve (V22) are opened to purge the remote gas supply pipe (L5).

2. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 1, characterized in that, The fuel tank (1) is equipped with a fuel supply pump. The outlet of the fuel supply pump is connected to the inlet of the high-pressure pump through a low-pressure LNG fuel pipe (L1). The outlet of the high-pressure pump is connected to the inlet of the high-pressure evaporator (4) through a high-pressure LNG fuel pipe (L2). The outlet of the high-pressure evaporator (4) is connected to the inlet of the buffer tank (5) through a pipeline. The outlet of the buffer tank (5) is connected to the inlet of the ESD main valve (V14) of the gas equipment through a high-pressure NG gas pipe (L4). The outlet of the ESD main valve (V14) is connected to the inlet of the auxiliary main valve (V15) through a long-distance gas supply pipe (L5). The outlet of the auxiliary main valve (V15) is connected to the inlet of the gas valve group unit (6) through a pipeline. The outlet of the gas valve group unit (6) is connected to the inlet of the high-pressure main unit (7) through a pipeline.

3. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 2, characterized in that, The high-voltage main unit (7) is located in the engine room, and the fuel tank (1) is located on the main deck away from the engine room or in the fuel tank location. A GVT room and a fuel preparation room are provided between the fuel tank (1) and the engine room. The GVT room is close to the engine room, and the fuel preparation room is close to the fuel tank (1). The gas valve assembly unit (6) and the auxiliary main valve (V15) are located in the GVT room, which is equipped with a ventilation system. The high-pressure pump, high-pressure evaporator (4), ESD main valve (V14) and buffer tank (5) are located in the fuel preparation room, which is equipped with a ventilation system.

4. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 1, characterized in that, The long-distance gas supply pipe (L5) is provided with several expansion bends (L13).

5. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 2, characterized in that, The return port of the high-pressure pump is connected to the fuel tank (1) through the return pipe (L3). It also includes a pressure relief pipe (L12), the two ends of which are connected to a long-distance gas supply pipe (L5) and a return pipe (L3) respectively, and a pressure relief valve (V31) is provided on the pressure relief pipe (L12).

6. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 2, characterized in that, The outlet of the gas valve assembly unit (6) is connected to the inlet of the high-pressure host (7) through a double-walled pipe (L6).

7. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 3, characterized in that, The ventilation systems of both the GVT room and the fuel preparation room are redundant.

8. The long-distance transmission high-pressure main engine LNG fuel supply system according to claim 2, characterized in that, The long-distance gas supply pipe (L5) is equipped with a pipe heat tracing device.

9. A control method for a long-distance transmission high-pressure main engine LNG fuel supply system, using the long-distance transmission high-pressure main engine LNG fuel supply system according to any one of claims 1 to 8, characterized in that, The high-pressure main unit (7) switches from fuel oil mode to natural gas mode. The fuel tank (1) supplies gas to the high-pressure main unit (7) through the long-distance gas supply pipe (L5). When the time to establish gas supply pressure exceeds the start-up time of the main unit, the ESD main valve (V14) and the auxiliary main valve (V15) are closed, so that the gas in the long-distance gas supply pipe (L5) is pressure-held and stored. The gas pressure-held and stored time is less than the process requirement time. The high-pressure main unit (7) switches from fuel oil mode to natural gas mode again, opens the ESD main valve (V14) and auxiliary main valve (V15), and the fuel tank (1) supplies gas to the high-pressure main unit (7) again through the long-distance gas supply pipe (L5).

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