Security system for ammonia-fueled low-speed engine test bed and control method

Abstract

Disclosed are a security system for an ammonia-fueled low-speed engine test bed and a control method. The system comprises a plurality of two-way solenoid valves, a plurality of one-way valves, a plurality of pressure sensors, a supply fan, an exhaust fan, a manual two-way valve, a buffer tank, an ammonia detector, a three-way solenoid valve, a flow meter, and an ammonia vapor tank located outdoors. The control method comprises: a) a sealing performance test before startup of an ammonia-fueled engine; b) the ammonia-fueled engine starting normally and operating without leakage; c) startup and operation of an ammonia-fueled low-speed engine under the condition of minor leakage not exceeding 200 ppm; and d) startup and operation of the ammonia-fueled low-speed engine under the condition of severe leakage exceeding 200 ppm. In the present invention, under different operating conditions of minor or severe ammonia fuel leakage, the leaked ammonia fuel is recovered into the outdoor ammonia vapor tank, ensuring the safety of on-site personnel, thereby providing a reliable guarantee for a safe and reliable test run of ammonia-fueled low-speed engines.

Description

Safety System and Control Methods for Ammonia Fuel Low-Speed ​​Engine Test Stand Technical Field

[0001] This invention relates to a test bench for new energy engines, and more particularly to a safety system and control method for bench testing of ammonia fuel low-speed (n≤300rpm) engines, belonging to the field of new energy engine technology. Background Technology

[0002] With the gradual implementation of the "carbon peaking and carbon neutrality" dual-carbon strategy, ammonia fuel, as a zero-carbon fuel, is receiving increasing attention and has made initial progress in the research and development of marine low-speed engines. Currently, major global marine low-speed engine manufacturers are actively promoting the development of ammonia-fueled low-speed engines. However, ammonia is gaseous at room temperature and pressure, and high concentrations are toxic to humans and corrosive to carbon steel. Therefore, effective ammonia leakage prevention measures must be taken during bench testing of ammonia-fueled low-speed engines to prevent injury to on-site personnel and ensure safe and reliable commissioning and testing of the engines, thus promoting the zero-carbon development of marine engines. Technical issues

[0003] The purpose of this invention is to provide a safety system and control method for a marine ammonia-fueled low-speed engine test bench, so as to meet the safety requirements of ammonia-fueled low-speed engine testing, and to effectively and reliably handle ammonia leaks in order to ensure the safety of on-site test personnel. Technical solutions

[0004] This invention is achieved through the following technical solution:

[0005] A safety system for a low-speed ammonia fuel engine test bench includes several two-way solenoid valves, several one-way valves, several pressure sensors, a blower, an exhaust fan, a manual two-way valve, a buffer tank, an ammonia detector, a three-way solenoid valve, and a flow meter located indoors where the low-speed ammonia fuel engine is located, as well as an ammonia vapor tank located outdoors. A low-pressure nitrogen pipe passes through a first two-way solenoid valve, and a high-pressure nitrogen pipe passes through a second two-way solenoid valve, both merging into a single connecting pipe. This connecting pipe is then connected to a fifth two-way solenoid valve and a fifth one-way valve, and then splits into two branches. One branch connects to the D3 port of the nitrogen fuel leak pipe at the bottom of the ammonia fuel engine, and the other branch extends through the wall and connects to one end of the ammonia vapor tank. At the junction of the low-pressure and high-pressure nitrogen pipes, the connecting pipe further splits into two branches. One branch passes through the D3 port of the first two-way solenoid valve, and the other branch connects to the third two-way solenoid valve, and the third branch connects to the fourth two-way solenoid valve, and the fourth branch connects to the fifth one-way valve, and the fifth ... The three-way solenoid valve and the first one-way valve are connected to the outer pipe of the D2 output double-walled pipe of the ammonia fuel low-speed engine; the connecting pipe of the outer pipe of the D2 output double-walled pipe also passes through the eighth two-way solenoid valve, the ammonia detector, the exhaust fan, the bypass end of the three-way solenoid valve, and the direct E2 end of the three-way solenoid valve, and then passes through the wall to connect to the other end of the ammonia vapor tank; another branch passes through the fourth two-way solenoid valve and the second one-way valve and then splits into two branches. The connecting pipe of one branch is connected to the outer pipe of the D1 input double-walled pipe of the ammonia fuel low-speed engine; the other branch passes through the sixth two-way solenoid valve, the third one-way valve, the flow meter, the buffer tank, the fourth one-way valve, and the air supply fan, and is connected to the atmospheric input pipe port of B2 at normal temperature and pressure; one end of the buffer tank is connected to the 0.7~1.0 through the manual two-way valve and the seventh solenoid valve. The dry compressed air input pipe with a pressure of MPa is connected to port B1; the signal lines of the PLC controller are connected to the control terminals of each two-way solenoid valve, each pressure sensor, the supply fan, the exhaust fan, and the flow meter.

[0006] The objective of this invention can also be achieved in one step through the following technical measures.

[0007] Furthermore, the first pressure sensor is connected in parallel to the connecting pipeline where the first two-way solenoid valve and the second two-way solenoid valve meet; the second pressure sensor is connected in parallel to the connecting pipeline between the first one-way valve and the outer pipe of the D2 output double-walled pipe of the ammonia fuel low-speed engine; and the third pressure sensor is connected in parallel to the connecting pipeline between the flow meter and the buffer tank.

[0008] Furthermore, the pressure of the low-pressure nitrogen pipe is 0.3 MPa, and the pressure of the high-pressure nitrogen pipe is 3.0 MPa.

[0009] Furthermore, the pressure detection range of the first pressure sensor, the second pressure sensor, and the third pressure sensor is 0~15MPa, and the output current signal is 4~20mA.

[0010] Furthermore, the ammonia detector has a measurement range of 0~1000ppm and a measurement accuracy of ≤1ppm; the output current signal is 4~20mA.

[0011] Furthermore, the air volume of the blower is 60m³. 3 / h, the air volume of the exhaust fan is 40m³ / h. 3 / h.

[0012] Furthermore, the capacity of the buffer tank is 0.8–1.2 m³. 3 .

[0013] A control method for a safety system of a low-speed ammonia fuel engine test bench includes the following corresponding steps for different operating conditions:

[0014] a) Sealing performance test before starting the ammonia fuel engine

[0015] a1) The PLC controller sends a signal to open the second two-way solenoid valve and close the third, fourth, sixth, and eighth two-way solenoid valves. The 3MPa high-pressure nitrogen gas input from the high-pressure nitrogen pipe input port A2 passes through the second two-way solenoid valve and is then sealed in the connecting pipeline.

[0016] a2) When the first pressure sensor detects a pressure of 3.0 MPa, the PLC controller sends a signal to close the second two-way solenoid valve and maintain the system pressure for 10 minutes. If the nitrogen pressure drops by no more than 10 kPa within 10 minutes, the system meets the sealing requirements.

[0017] b) The ammonia fuel engine starts normally and operates without leakage.

[0018] b1) In a dry environment with an air temperature exceeding 20°C and an air humidity less than 30%, when the ammonia fuel engine is running normally, ordinary air is used to ventilate the outer wall of the double-walled pipe. The PLC controller sends a signal to start the air supply fan and opens the sixth two-way solenoid valve, the eighth two-way solenoid valve, the exhaust fan, and connects the bypass end of the three-way solenoid valve and the direct E1 end of the three-way solenoid valve. Normal temperature and pressure air enters from the B2 air inlet port of the input pipe, passes through the air supply fan, the fourth one-way valve, the buffer tank, the flow meter, the third one-way valve, and the sixth two-way solenoid valve in sequence, and enters the outer pipe of the D1 input double-walled pipe of the ammonia fuel low-speed engine. Then it is output from the outer pipe of the D2 output double-walled pipe of the ammonia fuel low-speed engine, passes through the eighth two-way solenoid valve, the ammonia detector, the exhaust fan, the connected bypass end of the three-way solenoid valve, and the direct E1 end of the three-way solenoid valve in sequence, and is discharged from the C port of the exhaust pipe that passes through the wall.

[0019] b2) In an environment where the air temperature does not exceed 20°C and the air humidity is less than 30%, open the manual two-way valve. At the same time, the PLC controller sends a signal to open the sixth, seventh, and eighth two-way solenoid valves respectively, and connect the bypass end of the three-way solenoid valve and the direct E1 end of the three-way solenoid valve. Dry compressed air at 0.7 MPa is input from the B1 input port of the intake pipe. It passes through the seventh two-way solenoid valve, the manual two-way valve, the buffer tank, the flow meter, the third check valve, and the sixth two-way solenoid valve in sequence. It enters from the outer pipe of the D1 input double-wall pipe of the ammonia fuel low-speed engine, and then exits from the outer pipe of the D2 output double-wall pipe of the ammonia fuel low-speed engine. It passes through the eighth solenoid valve, the ammonia detector, and the exhaust fan in sequence. Then, it passes through the connected bypass end of the three-way solenoid valve and the direct E1 end of the three-way solenoid valve, and is discharged from the C port of the exhaust pipe leading to the outside.

[0020] c) Start-up operation of ammonia-fueled low-speed engines with a slight leak of no more than 200 ppm

[0021] [Corrected according to Rule 91, December 16, 2025] When the ammonia detector detects a slight leak of ammonia fuel not exceeding 200 ppm, the PLC controller sends a signal to open the first two-way solenoid valve and the fourth two-way solenoid valve, and close the third two-way solenoid valve. At this time, nitrogen gas at a pressure of 0.3 MPa enters from port A1 of the low-pressure nitrogen pipe, passes through the first two-way solenoid valve, the fourth two-way solenoid valve, and the second check valve in sequence, enters from the outer pipe of the ammonia fuel D1 input double-wall pipe, and exits from the outer pipe of the ammonia fuel D2 output double-wall pipe, and so on. After passing through the eighth solenoid valve, ammonia detector, and exhaust fan, the leaked ammonia fuel is then output from the bypass end of the three-way solenoid valve and the direct E2 end of the three-way solenoid valve, and then enters the outdoor ammonia vapor tank through the connecting pipeline to collect the leaked ammonia fuel. At the same time, the PLC controller sends a signal to open the fifth two-way solenoid valve for 20 seconds every 10 minutes. Nitrogen gas with a pressure of 0.3 MPa input from the A1 port of the low-pressure nitrogen pipe passes through the fifth one-way valve and merges with the ammonia fuel leaking from the nitrogen fuel D3 leak port at the bottom of the ammonia fuel engine, and is blown back to the ammonia vapor tank for collecting ammonia fuel.

[0022] d) Start-up and operation of ammonia-fueled low-speed engines under severe leakage exceeding 200 ppm

[0023] [Corrected according to Rule 91, December 16, 2025] When the ammonia detector detects a serious leak of ammonia fuel exceeding 200 ppm, the PLC controller sends a signal to open the first two-way solenoid valve, the second two-way solenoid valve, the fourth two-way solenoid valve, and the eighth two-way solenoid valve, and close the third two-way solenoid valve. High-pressure nitrogen gas at 3 MPa, input from port A2 of the high-pressure nitrogen pipe, passes sequentially through the first two-way solenoid valve, the fourth two-way solenoid valve, and the second check valve, and is input into the outer pipe of the ammonia fuel D1 input double-wall pipe. It then passes through the outlet of the ammonia fuel D2 output double-wall pipe, and then sequentially through the eighth two-way solenoid valve, the ammonia detector, the exhaust fan, and then through the bypass end of the three-way solenoid valve and the direct connection end of the three-way solenoid valve to E2. Finally, it carries the leaked ammonia fuel into the outdoor ammonia vapor tank via the connecting pipeline. Simultaneously, the PLC controller sends a signal to open the fifth two-way solenoid valve. The high-pressure nitrogen gas passes sequentially through the fifth two-way solenoid valve and the fifth check valve, blowing the leaked ammonia fuel from port D3 at the bottom of the ammonia fuel engine back into the ammonia vapor tank for collecting ammonia fuel. 。 Beneficial effects

[0024] This invention employs a structure combining multiple two-way solenoid valves, multiple one-way valves, a three-way solenoid valve, a blower, an exhaust fan, and an ammonia detector via connecting pipes. Through different combinations of solenoid valve opening and closing methods, and by using different input types such as high-pressure nitrogen, low-pressure nitrogen, compressed air, and ambient air, it provides a safe and reliable safety system and control method for ammonia-fueled low-speed engine bench testing. This system enables sealing performance testing before ammonia-fueled engine startup, and allows for the recovery of leaked ammonia fuel into an outdoor ammonia evaporator under different operating conditions: normal engine startup without leakage, minor ammonia leakage, and severe ammonia leakage. This effectively reduces the risk of harm to personnel in the event of ammonia leakage during ammonia-fueled low-speed engine bench testing, ensuring the safety of on-site personnel and providing a reliable guarantee for the safe and reliable testing of ammonia-fueled low-speed engines.

[0025] The advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments, which are given by way of example only with reference to the accompanying drawings. Attached Figure Description

[0026] Figure 1 is a schematic diagram of the safety system of the ammonia fuel low-speed engine test stand. Embodiments of the present invention

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] As shown in Figure 1, the safety system for the ammonia fuel low-speed engine test bench of the present invention includes eight two-way solenoid valves, five one-way valves, three pressure sensors, a blower 41, an exhaust fan 42, a manual two-way valve 5, a buffer tank 6, an ammonia detector 7, a three-way solenoid valve 8, and a flow meter 9 located in the room where the ammonia fuel low-speed engine 100 is located, and an ammonia vapor tank 20 located outdoors. The low-pressure nitrogen pipe 101 passes through the first two-way solenoid valve 11, and the high-pressure nitrogen pipe 102 passes through the second two-way solenoid valve 12 and then merges into a connecting pipe 103. The connecting pipe 103 is connected to the fifth two-way solenoid valve 15 and the fifth one-way valve 25 in sequence and then splits into two paths. One connecting pipe 103 is connected to the D3 port of the nitrogen fuel leakage pipe 104 at the bottom of the ammonia fuel engine 100, and the other connecting pipe 103 passes through the wall 200 and is connected to one end of the ammonia vapor tank 10. The connecting pipe 103 at the junction of the low-pressure nitrogen pipe 101 and the high-pressure nitrogen pipe 102 splits into two branches. One branch passes through the third two-way solenoid valve 13 and the first one-way valve 21 in sequence, and then connects to the outer pipe of the D2 output double-wall pipe 105 of the ammonia fuel low-speed engine 100. The connecting pipe 103 of the outer pipe of the D2 output double-wall pipe 105 also passes through the eighth two-way solenoid valve 18, the ammonia detector 7, the exhaust fan 42, the bypass end 81 of the three-way solenoid valve, and the direct E2 end 82 of the three-way solenoid valve in sequence, and then passes through the wall 200 to connect to the other end of the ammonia vapor tank 20. Another branch line passes through the fourth two-way solenoid valve 14 and the second one-way valve 22 in sequence, then splits into two branches. One branch line's connecting pipe 103 is connected to the outer pipe of the D1 input double-wall pipe 106 of the ammonia fuel low-speed engine 100. The other branch line passes through the sixth two-way solenoid valve 16, the third one-way valve 23, the flow meter 9, the buffer tank 6, the fourth one-way valve 24, and the air supply fan 41 in sequence, and is connected to the B2 atmospheric input pipe 108 at normal temperature and pressure. One end of the buffer tank 6 is connected to the B1 port of the dry compressed air input pipe 108 at a pressure of 0.7~1.0 MPa in sequence through the manual two-way valve 5 and the seventh solenoid valve 17. The signal line 301 of the PLC controller 30 is connected to the control terminals of each two-way solenoid valve, each pressure sensor, the air supply fan 41, the exhaust fan 42, and the flow meter 9, respectively.

[0029] The first pressure sensor 31 is connected in bypass of the connecting pipe 103 where the first two-way solenoid valve 11 and the second two-way solenoid valve 12 meet. The second pressure sensor 32 is connected in bypass of the connecting pipe 103 where the first one-way valve 21 connects to the outer pipe of the D2 output double-walled pipe 106 of the ammonia fuel low-speed engine. The third pressure sensor 33 is connected in bypass of the connecting pipe 103 between the flow meter 9 and the buffer tank 6. The pressure of the low-pressure nitrogen pipe 101 is 0.3 MPa, and the pressure of the high-pressure nitrogen pipe 102 is 3.0 MPa.

[0030] The pressure detection range of the first pressure sensor 31, the second pressure sensor 32, and the third pressure sensor 33 is 0~15Mpa, and the output current signal is 4~20mA.

[0031] The ammonia detector 7 has a measurement range of 0~1000ppm and a measurement accuracy of ≤1ppm; the output current signal is 4~20mA. The air volume of the blower 41 is 60m³ / h. 3 / h, the air volume of exhaust fan 42 is 40m³ / h. 3 / h. Controlled by the PLC controller 30, the supply fan 41 and exhaust fan 42 ensure an air exchange rate of 30-40 times per hour, with each exchange equal to the total capacity of all double-walled outer pipes. The buffer tank 6 has a capacity of 0.8-1.2 m³. 3 It is mainly used to ensure the relative stability of the supply gas pressure. The main function of the ammonia vapor tank 20 is to separate and recover ammonia from the mixed gas, preventing it from being directly discharged into the atmosphere.

[0032] A control method for a safety system of a low-speed ammonia fuel engine test bench includes the following corresponding steps for different operating conditions:

[0033] a) Sealing performance test of ammonia fuel engine before 100 start-up

[0034] a1) The PLC controller 30 sends a signal to open the second two-way solenoid valve 12 and close the third two-way solenoid valve 13, the fourth two-way solenoid valve 14, the sixth two-way solenoid valve 16 and the eighth two-way solenoid valve 18. The 3.0 MPa high-pressure nitrogen gas input from the A2 port of the high-pressure nitrogen pipe 102 passes through the second two-way solenoid valve 12 and is then sealed in the connecting pipe 103.

[0035] a2) When the first pressure sensor 31 detects a pressure of 3.0 MPa, the PLC controller 30 sends a signal to close the second two-way solenoid valve 12 and maintain the system pressure for 10 minutes. If the nitrogen pressure decreases by no more than 10 kPa within 10 minutes, the system meets the sealing requirements.

[0036] b) The ammonia fuel engine starts normally and operates without leakage.

[0037] b1) In a dry environment with an air temperature exceeding 20°C and an air humidity of less than 30%, when the ammonia fuel engine 100 is operating normally, ordinary air is used to ventilate the inner wall of the double-walled pipe. The PLC controller 30 sends a signal to start the blower 41, and opens the sixth two-way solenoid valve 16, the eighth two-way solenoid valve 18, the exhaust fan 42, and connects the bypass terminal 83 of the three-way solenoid valve and the direct E1 terminal 81 of the three-way solenoid valve. Atmospheric air at normal temperature and pressure enters through the B2 atmospheric inlet port of the input pipe 108, passes sequentially through the blower 41, the fourth one-way valve 24, the buffer tank 6, the flow meter 9, the third one-way valve 23, and the sixth two-way solenoid valve 16, and enters the outer pipe of the D1 input double-wall pipe 105 of the ammonia fuel low-speed engine 100. Then it is output from the outer pipe of the D2 output double-wall pipe 106 of the ammonia fuel low-speed engine 100, passes sequentially through the eighth two-way solenoid valve 18, the ammonia detector 7, the exhaust fan 42, the bypass end 83 of the three-way solenoid valve, and the direct E1 end 81 of the three-way solenoid valve, and is discharged from the C port of the exhaust pipe 109 that passes through the wall 200.

[0038] b2) In an environment where the ambient temperature does not exceed 20°C and the air humidity is less than 30%, open the manual two-way valve 5. Simultaneously, the PLC controller 30 sends a signal to open the sixth two-way solenoid valve 16, the seventh two-way solenoid valve 17, and the eighth two-way solenoid valve 18, respectively. This connects the bypass terminal 83 of the three-way solenoid valve and the direct E1 terminal 81 of the three-way solenoid valve, allowing 0.7 MPa dry compressed air to be input from the B1 input port of the air inlet pipe 107. The compressed air then passes through the seventh two-way solenoid valve 17 and the manual two-way valve 5 in sequence. 5. The buffer tank 6, flow meter 9, third check valve 23 and sixth two-way solenoid valve 16 enter from the outer pipe of the D1 input double-wall pipe 105 of the ammonia fuel low-speed engine 100, and then exit from the outer pipe of the D2 output double-wall pipe 106 of the ammonia fuel low-speed engine 100. They pass through the eighth solenoid valve 18, ammonia detector 7 and exhaust fan 42 in sequence, and then through the bypass end 83 of the three-way solenoid valve and the direct E1 end 81 of the three-way solenoid valve, and are discharged from the C port of the exhaust pipe 109 leading to the outside.

[0039] c) Start-up operation of ammonia-fueled low-speed engines with a slight leak of no more than 200 ppm

[0040] [Correction 16.12.2025 according to Rule 91] When the ammonia detector 7 detects a slight leak of ammonia fuel of no more than 200 ppm, the PLC controller 30 sends a signal to open the first two-way solenoid valve 11 and the fourth two-way solenoid valve 14 respectively, and close the third two-way solenoid valve 13. At this time, nitrogen gas with a pressure of 0.3 MPa enters from the A1 port of the low-pressure nitrogen pipe 101, passes through the first two-way solenoid valve 11, the fourth two-way solenoid valve 14 and the second one-way valve 22 in sequence, enters from the outer pipe of the ammonia fuel D1 input double-wall pipe 105, and then exits from the outer pipe of the ammonia fuel D2 output double-wall pipe 106. It passes through the eighth solenoid valve 18, the ammonia detector 7 and the exhaust fan 42 in sequence, and then exits from the bypass end 83 of the three-way solenoid valve and the direct end E2 end 82 of the three-way solenoid valve. Finally, it enters the outdoor ammonia vapor tank 20 through the connecting pipe 103 to collect the leaked ammonia fuel. At the same time, the PLC controller 30 sends a signal to open the fifth two-way solenoid valve 15 every 10 minutes and continue for 20 seconds. Nitrogen gas with a pressure of 0.3 MPa is input from the A1 port of the low-pressure nitrogen pipe 101. After passing through the fifth one-way valve 25, it is combined with the ammonia fuel leaking from the nitrogen fuel D3 leak port 104 at the bottom of the ammonia fuel low-speed engine and blown back to the ammonia vapor tank 20 for collecting ammonia fuel.

[0041] d) Start-up operation of ammonia-fueled low-speed engine 100 under severe leakage exceeding 200 ppm

[0042] [Correction based on Rule 91, December 16, 2025] When the ammonia detector 7 detects a serious leak of ammonia fuel exceeding 200 ppm, the PLC controller 30 sends a signal to open the first two-way solenoid valve 11, the second two-way solenoid valve 12, the fourth two-way solenoid valve 14, and the eighth two-way solenoid valve 18, and close the third two-way solenoid valve 13. High-pressure nitrogen gas at 3.0 MPa, input from port A2 of the high-pressure nitrogen pipe 101, passes sequentially through the first two-way solenoid valve 11, the fourth two-way solenoid valve 14, and the second one-way valve 22, then into the outer pipe of the ammonia fuel input double-wall pipe 105 via the ammonia fuel D1 input double-wall pipe 106, and then through the outlet of the ammonia fuel output double-wall pipe 106 via the ammonia fuel D2 output double-wall pipe 106. It then passes sequentially through the eighth two-way solenoid valve 18, the ammonia detector 7, the exhaust fan 42, and then through the bypass end 83 of the three-way solenoid valve and the direct E2 end 82 of the three-way solenoid valve, before finally carrying the leaked ammonia fuel into the outdoor ammonia vapor tank 20 via the connecting pipe 103. At the same time, the PLC controller 30 sends a signal to open the fifth two-way solenoid valve 15. High-pressure nitrogen gas passes through the fifth two-way solenoid valve 15 and the fifth one-way valve 25 in sequence, blowing the ammonia fuel leaking from the bottom D3 port 104 of the ammonia fuel engine 100 back to the ammonia vapor tank 20 for collecting ammonia fuel.

[0043] In addition to the above embodiments, the present invention may have other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A safety system for a low-speed ammonia-fueled engine test bench, comprising several two-way solenoid valves, several one-way valves, several pressure sensors, a blower, an exhaust fan, a manual two-way valve, a buffer tank, an ammonia detector, a three-way solenoid valve, and a flow meter located in the room housing the low-speed ammonia-fueled engine, and an ammonia vapor tank located outdoors; characterized in that, The low-pressure nitrogen pipe merges into a single connecting pipe after passing through the first two-way solenoid valve and the high-pressure nitrogen pipe after passing through the second two-way solenoid valve. This connecting pipe then branches into two separate lines after being connected sequentially to the fifth two-way solenoid valve and the fifth check valve. One connecting pipe connects to the nitrogen fuel leak pipe D3 port at the bottom of the ammonia fuel engine, while the other connecting pipe passes through the wall and connects to one end of the ammonia vapor tank. At the junction of the low-pressure and high-pressure nitrogen pipes, the connecting pipe further branches into two branches. One branch passes sequentially through the third two-way solenoid valve and the first check valve, then connects to the outer pipe of the D2 output double-walled pipe of the ammonia fuel low-speed engine. The connecting pipe of the outer pipe of the D2 output double-walled pipe also... The first branch passes through the eighth two-way solenoid valve, ammonia detector, exhaust fan, three-way solenoid valve bypass terminal, and three-way solenoid valve direct E2 terminal in sequence, then exits the wall and connects to the other end of the ammonia vapor tank; the second branch passes through the fourth two-way solenoid valve and the second one-way valve in sequence, then splits into two branches. One branch connects to the outer pipe of the D1 input double-wall pipe of the ammonia fuel low-speed engine; the other branch passes through the sixth two-way solenoid valve, the third one-way valve, flow meter, buffer tank, fourth one-way valve, and air supply fan in sequence, and connects to the B2 port of the atmospheric input pipe at normal temperature and pressure; one end of the buffer tank is connected to the B1 port of the dry compressed air input pipe with a pressure of 0.7~1.0 MPa in sequence through the manual two-way valve and the seventh solenoid valve; the signal lines of the PLC controller are connected to the control terminals of each two-way solenoid valve, each pressure sensor, air supply fan, exhaust fan, and flow meter respectively.

2. The safety system for the ammonia fuel low-speed engine test stand as described in claim 1, characterized in that: The first pressure sensor is connected in parallel to the connecting pipeline where the first two-way solenoid valve and the second two-way solenoid valve meet; the second pressure sensor is connected in parallel to the connecting pipeline between the first check valve and the outer pipe of the D2 output double-walled pipe of the ammonia fuel low-speed engine; the third pressure sensor is connected in parallel to the connecting pipeline between the flow meter and the buffer tank.

3. The safety system for the ammonia fuel low-speed engine test stand as described in claim 1, characterized in that: The pressure of the low-pressure nitrogen pipe is 0.3 MPa, and the pressure of the high-pressure nitrogen pipe is 3.0 MPa.

4. The safety system for the ammonia fuel low-speed engine test stand as described in claim 1, characterized in that: The pressure detection range of the first, second, and third pressure sensors is 0~15 MPa, and the output current signal is 4~20 mA.

5. The safety system for the ammonia fuel low-speed engine test stand as described in claim 1, characterized in that: The ammonia detector has a measurement range of 0~1000ppm and a measurement accuracy of ≤1ppm; the output current signal is 4~20mA.

6. The safety system for the ammonia fuel low-speed engine test stand as described in claim 1, characterized in that: The air volume of the blower is 60m³. 3 / h, the air volume of the exhaust fan is 40m³ / h. 3 / h.

7. The safety system for the ammonia fuel low-speed engine test stand as described in claim 1, characterized in that: The buffer tank has a capacity of 0.8–1.2 m³. 3 .

8. [Correction 16.12.2025 according to Rule 91] A control method for a safety system of an ammonia fuel low-speed engine test stand as described in any one of claims 1 to 7, characterized in that: The corresponding steps for the following different working conditions are included: a) Sealing performance test before starting the ammonia fuel engine a1) The PLC controller sends a signal to open the second two-way solenoid valve and close the third, fourth, sixth, and eighth two-way solenoid valves. The 3MPa high-pressure nitrogen gas input from the A2 port of the high-pressure nitrogen pipe passes through the second two-way solenoid valve and is then sealed in the connecting pipeline. a2) When the first pressure sensor detects a pressure of 3.0 MPa, the PLC controller sends a signal to close the second two-way solenoid valve and maintain the system pressure for 10 minutes. If the nitrogen pressure decreases by no more than 10 kPa within 10 minutes, the system meets the sealing requirements. b) The ammonia fuel engine starts normally and operates without leaks. b1) In a dry environment with an air temperature exceeding 20°C and an air humidity less than 30%, when the ammonia fuel engine is running normally, ordinary air is used to ventilate the outer wall of the double-walled pipe. The PLC controller sends a signal to start the air supply fan and opens the sixth two-way solenoid valve, the eighth two-way solenoid valve, the exhaust fan, and connects the bypass end of the three-way solenoid valve and the direct E1 end of the three-way solenoid valve. Normal temperature and pressure air enters from the B2 air inlet port of the input pipe, passes through the air supply fan, the fourth one-way valve, the buffer tank, the flow meter, the third one-way valve, and the sixth two-way solenoid valve in sequence, and enters the outer pipe of the D1 input double-walled pipe of the ammonia fuel low-speed engine. Then it is output from the outer pipe of the D2 output double-walled pipe of the ammonia fuel low-speed engine, passes through the eighth two-way solenoid valve, the ammonia detector, the exhaust fan, the connected bypass end of the three-way solenoid valve, and the direct E1 end of the three-way solenoid valve in sequence, and is discharged from the C port of the exhaust pipe that passes through the wall. b2) In an environment where the air temperature does not exceed 20°C and the air humidity is less than 30%, open the manual two-way valve. At the same time, the PLC controller sends a signal to open the sixth, seventh, and eighth two-way solenoid valves respectively, and connect the bypass end of the three-way solenoid valve and the direct E1 end of the three-way solenoid valve. Dry compressed air at 0.7 MPa is input from the B1 input port of the intake pipe. It passes through the seventh two-way solenoid valve, the manual two-way valve, the buffer tank, the flow meter, the third check valve, and the sixth two-way solenoid valve in sequence. It enters from the outer pipe of the D1 input double-wall pipe of the ammonia fuel low-speed engine and exits from the outer pipe of the D2 output double-wall pipe of the ammonia fuel low-speed engine in sequence. It passes through the eighth solenoid valve, the ammonia detector, and the exhaust fan in sequence. Then, it passes through the connected bypass end of the three-way solenoid valve and the direct E1 end of the three-way solenoid valve and is discharged from the C port of the exhaust pipe leading to the outside. c) Start-up operation of ammonia-fueled low-speed engines with a slight leak of no more than 200 ppm When the ammonia detector detects a slight leak of ammonia fuel not exceeding 200 ppm, the PLC controller sends a signal to open the first and fourth two-way solenoid valves and close the third two-way solenoid valve. At this time, nitrogen gas at a pressure of 0.3 MPa enters from port A1 of the low-pressure nitrogen pipe, passes through the first two-way solenoid valve, the fourth two-way solenoid valve, and the second check valve in sequence, enters from the outer pipe of the ammonia fuel inlet double-wall pipe D1, and exits from the outer pipe of the ammonia fuel outlet double-wall pipe D2, passing through the eighth solenoid valve and the ammonia detector in sequence. The device and exhaust fan then output the leaked ammonia fuel from the bypass end of the three-way solenoid valve and the direct E2 end of the three-way solenoid valve, and then through the connecting pipeline into the outdoor ammonia vapor tank to collect the leaked ammonia fuel; at the same time, the PLC controller sends a signal to open the fifth two-way solenoid valve for 20 seconds every 10 minutes, and the nitrogen gas with a pressure of 0.3Mpa input from the A1 port of the low-pressure nitrogen pipe passes through the fifth one-way valve and merges with the ammonia fuel leaking from the nitrogen fuel D3 leak port at the bottom of the ammonia fuel engine, and blows it back into the ammonia vapor tank to collect the ammonia fuel; d) Start-up and operation of ammonia-fueled low-speed engines under severe leakage exceeding 200 ppm When the ammonia detector detects a severe leak of ammonia fuel exceeding 200 ppm, the PLC controller sends a signal to open the first two-way solenoid valve, the second two-way solenoid valve, the fourth two-way solenoid valve, and the eighth two-way solenoid valve, while closing the third two-way solenoid valve. High-pressure nitrogen gas at 3.0 MPa, input from port A2 of the high-pressure nitrogen pipe, passes sequentially through the first two-way solenoid valve, the fourth two-way solenoid valve, and the second check valve, then into the outer pipe of the ammonia fuel input double-wall pipe (D1), and then through the outlet of the ammonia fuel output double-wall pipe (D2). It then passes sequentially through the eighth two-way solenoid valve, the ammonia detector, and the exhaust fan, before flowing through the bypass end of the three-way solenoid valve and the direct connection end of the three-way solenoid valve (E2). Finally, it carries the leaked ammonia fuel into the outdoor ammonia vapor tank via connecting pipes. Simultaneously, the PLC controller sends a signal to open the fifth two-way solenoid valve, and the high-pressure nitrogen gas passes sequentially through the fifth two-way solenoid valve and the fifth check valve, blowing the leaked ammonia fuel from port D3 at the bottom of the ammonia fuel engine back into the ammonia vapor tank.

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