A marine ammonia-electric hybrid power system with integrated cooling system

Abstract

The purpose of this invention is to provide a marine ammonia-electric hybrid power system with an integrated cooling system, including an ammonia fuel engine, a doubly-fed induction motor, a propeller, a gearbox, a diesel generator set, a fuel cell, an ammonia storage and supply system, a power distribution unit, a marine electrical grid, hydraulic components, and an integrated cooling system. The technical solution of this invention enables hybrid propulsion of the ammonia fuel engine and the doubly-fed induction motor, and coordinated power supply from the diesel generator set, fuel cell, and lithium battery, further improving the overall propulsion efficiency of the ship. A coordinated gas path scheme for the engine and fuel cell is proposed, enabling complementary advantages between the two and simplifying gas path design redundancy; an integrated cooling system is designed, improving the system's integration level.

Description

Technical Field

[0001] The present invention relates to a marine propulsion system, specifically a marine hybrid power system. Background Technology

[0002] Currently, marine power systems, which are mainly based on diesel engines, have the disadvantages of high pollution, low energy consumption, and high carbon emissions. Therefore, there is an urgent need to find a low-carbon and efficient power system to meet the increasingly stringent carbon reduction requirements and adapt to the future goals of low-carbonization and even zero carbon.

[0003] Ammonia fuel, as a clean fuel, is widely used in the chemical industry. As a zero-carbon fuel, it has also attracted increasing attention in the marine propulsion field in recent years. Although the concept of ammonia fuel engines has been proposed in the shipbuilding industry, mature products are still lacking due to technological limitations. On the one hand, there is a lack of comprehensive research on the performance of ammonia fuel engines; on the other hand, there is no clear technical solution for matching ammonia fuel engines with appropriate power systems. Therefore, the research and development of ammonia fuel engines is still in its initial stage, and hybrid power systems for ammonia fuel engines are currently a technological void.

[0004] Marine hybrid power systems combine the advantages of traditional internal combustion engine propulsion and pure electric propulsion. Hybrid systems offer significant advantages in overall energy efficiency, energy conservation and emission reduction, and vibration and noise reduction. Furthermore, compared to pure electric propulsion systems, they can achieve long driving ranges with smaller capacity batteries at a lower cost. Hybrid systems based on ammonia fuel engines can meet the requirements of zero-carbon power while mitigating the low efficiency and cold-start difficulties of ammonia fuel engines. The introduction of an electric motor can also improve the dynamic characteristics of ammonia fuel engines, achieving complementary advantages from multiple power sources. Hybrid systems based on ammonia fuel engines will become one of the best power forms for future zero-carbon power. Therefore, securing intellectual property rights for ammonia fuel engine hybrid systems is of great significance for gaining a competitive edge in international technology and protecting key technologies related to ammonia fuel engine hybrid power. Summary of the Invention

[0005] The purpose of this invention is to provide a marine ammonia-electric hybrid propulsion system with an integrated cooling system that enables hybrid propulsion of an ammonia fuel engine and an electric motor, an ammonia-diesel generator set, an energy storage device, and a fuel cell.

[0006] The objective of this invention is achieved as follows:

[0007] This invention discloses a marine ammonia-electric hybrid power system with an integrated cooling system, characterized by comprising: a variable-pitch propeller, an ammonia engine, an ammonia-diesel generator set, a doubly-fed induction motor, an ammonia fuel cell, a lithium-ion battery, a power grid, an ammonia storage tank, an oxygen storage tank, and an integrated cooling system. The ammonia engine is connected to the doubly-fed induction motor and the variable-pitch propeller via a clutch. The rotor excitation winding of the doubly-fed induction motor is connected to the output terminal of the ammonia fuel cell via a doubly-fed induction motor frequency converter. The stator winding of the doubly-fed induction motor is connected to the power grid. The lithium-ion battery is connected to the power grid via a lithium-ion battery inverter, and the ammonia fuel cell is connected to the power grid via an ammonia fuel cell inverter. The ammonia-diesel generator set is directly connected to the power grid. The ammonia storage tank is connected to the ammonia fuel cell via a first shut-off valve, a pressure regulating valve, a flame-retardant valve, and the first outlet of a seventh three-way valve. The ammonia outlet of the ammonia fuel cell is connected to the ammonia-diesel generator set via a first fuel pump, the first outlet of an eighth three-way valve, and a second flow meter. The deaerator is connected to the ammonia-diesel generator set via a second shut-off valve. The second flow meter is connected to the ammonia fuel cell. A portion of the exhaust gas from the exhaust pipe of the ammonia diesel generator enters the ammonia fuel cell through the second outlet of the third three-way valve and the first outlet of the second three-way valve. The exhaust gas generated by the ammonia fuel cell and the exhaust gas generated by the ammonia diesel generator are combined through the three-way valve to the exhaust pipe of the ammonia diesel generator. A portion of the exhaust gas in the exhaust pipe passes through the first outlet of the third three-way valve, the purification device, the first heat exchanger, and the second exhaust gas recirculation pump, and enters the intake pipe of the ammonia diesel generator through the sixth three-way valve. After the air is compressed by the turbocharger of the ammonia diesel generator, a portion enters the exhaust pipe through the second outlet of the fifth three-way valve, and a portion enters the intake pipe through the first outlet of the fifth three-way valve, the second heat exchanger, and the first outlet of the sixth three-way valve. The exhaust gas in the exhaust pipe is discharged into the atmosphere through the turbine, a portion is directly discharged into the atmosphere through the fourth three-way valve, and another portion enters the ammonia fuel cell through the fourth three-way valve and the second three-way valve.

[0008] The integrated cooling system includes a seawater pump, a freshwater pump, a plate heat exchanger, and an expansion tank. The seawater pump draws seawater through the second valve body into the plate heat exchanger, and then returns to the sea through the first valve body. The freshwater pump pumps freshwater from the expansion tank, which is divided into three parts after passing through the thirteenth-way valve, the ninth-way valve, and a flow meter. The first part passes through the seventh and eighth valve bodies to enter the accessory cooling circuit and the electronic device cooling circuit, respectively, and flows out through the ninth and tenth valve bodies. The second part enters the lubricating oil cooling circuit of the ammonia diesel generator set, and is divided into two paths at the outlet of the lubricating oil cooling circuit. The first path enters the cylinder liner water cooling circuit through the eleventh-way valve and the twelfth valve body, and the second path enters the ammonia fuel cell through the eleventh-way valve. The third part enters the lithium-ion battery through the sixteenth valve body and flows out through the seventeenth valve body. The cooling water flowing out from the lithium-ion battery, the ammonia fuel cell, and the cylinder liner water cooling circuit of the ammonia diesel generator set is collected at the twelfth-way valve, flows through the heat exchanger, and then exchanges heat with the seawater.

[0009] The present invention may also include:

[0010] 1. In the start-up mode, the inverter controls the doubly-fed induction motor to drive the ammonia engine to start. The power source of the doubly-fed induction motor is directly provided by the ammonia fuel cell controlled by the inverter. The ammonia fuel required by the fuel cell in the grid enters the ammonia fuel cell through the ammonia storage tank, the first shut-off valve, the pressure regulating valve, the flame retardant valve, the seventh three-way valve and the first flow meter. In cold environments, the ammonia diesel generator unit starts first. A portion of the exhaust gas produced by the exhaust pipe enters the ammonia fuel cell for preheating through the fourth three-way valve, the second three-way valve or the third three-way valve. After the fuel cell is preheated to the preset temperature, the ammonia fuel cell starts.

[0011] 2. In mechanical mode, the clutch is engaged, the doubly fed induction motor does not work, and the ammonia fuel engine drives the variable pitch propeller through the gearbox.

[0012] 3. In electric propulsion mode, the doubly-fed induction motor starts, the clutch disengages, the ammonia engine stops working, and the variable-pitch propeller is driven by the doubly-fed induction motor. When the ship's speed is low, the gearbox selects a high speed ratio gear; when the ship's speed is high, the gearbox selects a low speed ratio gear. When the ship is docked or berthed, the pitch of the variable-pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the gearbox selects a high speed ratio gear.

[0013] 4. In hybrid propulsion mode, the clutch engages, and the doubly fed induction motor and the ammonia fuel engine jointly drive the variable pitch propeller via a gearbox. The doubly fed induction motor is controlled by the ship's electrical network via a frequency converter. The ammonia fuel engine operates in constant power mode or optimal economic curve mode. The engine's operating range is optimized by adjusting the variable pitch propeller pitch ratio and the speed of the doubly fed induction motor.

[0014] 5. In power generation mode, the clutch engages, and part of the power from the ammonia fuel engine drives the doubly-fed induction motor to generate electricity, while another part of the power drives the variable-pitch propeller through the gearbox. The doubly-fed induction motor feeds power to the grid in two ways: when the ammonia engine speed is adjusted to the rated speed by adjusting the variable-pitch propeller pitch ratio to generate 50Hz frequency power, it directly feeds power to the ship's power grid. At this time, the frequency converter does not work, and the doubly-fed induction motor acts as an asynchronous motor; when the speed of the doubly-fed induction motor is less than the rated speed, it feeds power to the ship's power grid through a variable-voltage frequency converter.

[0015] The advantages of this invention are:

[0016] 1. This invention proposes a marine ammonia-electric hybrid power system with an integrated cooling system. It includes an ammonia fuel engine, a doubly-fed induction motor, a dual-ratio gearbox, and a clutch. With a wide power range, it can meet the power requirements of ships under various operating conditions, reducing pollutant and carbon dioxide emissions. The significant technical advantages are as follows: First, the use of a doubly-fed induction motor reduces the inverter capacity by 50% compared to traditional PTO induction or synchronous motors used in ships. Simultaneously, due to the inclusion of an ammonia fuel cell and a lithium-ion battery, the doubly-fed induction motor does not require a starter generator set during startup. The AC power required for the rotor windings of the doubly-fed induction motor is directly obtained from the DC power of the ammonia fuel cell and converted by the inverter. Compared to traditional doubly-fed induction motors, this eliminates the AC-DC-AC conversion stage, improving energy transfer efficiency. The dual-ratio gearbox design overcomes the limitation of the small slip range of the doubly-fed induction motor, which makes it difficult to meet the needs of low-speed navigation. Furthermore, the variable-pitch propeller design avoids the problem of low torque at low speeds, better meeting the high torque requirements of low-speed navigation and improving the propulsion efficiency of the power system. The combination of an ammonia fuel engine and a doubly-fed induction motor serves two purposes. First, the doubly-fed induction motor can adjust the working space of the ammonia fuel engine, thereby improving its efficiency. Second, it can solve the problem of starting difficulties in high-power ammonia fuel engines due to the high ignition point of ammonia fuel. Furthermore, ammonia fuel engines suffer from incomplete combustion and poor dynamic characteristics under low-load conditions. The doubly-fed induction motor can utilize rapid torque response for torque coordination control to meet navigation requirements.

[0017] 2. The ship's power grid utilizes an ammonia-diesel generator set equipped with lithium-ion batteries and an ammonia fuel cell. The lithium-ion batteries can perform peak shaving and valley filling of the power grid, ensuring the ammonia-diesel generator set operates at its optimal efficiency point, thus improving the grid system efficiency. Simultaneously, the ammonia fuel cell, as one of the energy sources, can coordinate with the lithium-ion batteries to optimize the efficiency of the ammonia-diesel generator set, and can also optimize the operating point itself. This combined optimization approach improves the overall efficiency of the power grid and meets the grid's power demand. The specific technical effects are as follows: When grid power demand is low, the ammonia fuel cell and ammonia-diesel generator set operate in a high-efficiency range, with the remaining power charging the lithium-ion batteries. When grid power demand is high or exceeds the rated power of the ammonia-diesel generator set and ammonia fuel cell, the lithium-ion batteries discharge to meet the power demand, ensuring high-efficiency output from both the ammonia-diesel generator set and the ammonia fuel cell. The lithium-ion battery configuration leverages its high power output response to meet the dynamic power needs of the ship, thereby reducing operating fluctuations of the ammonia-diesel generator set and preventing increased engine emissions under extreme operating conditions. Furthermore, lithium-ion batteries and ammonia fuel cells can serve as backup power sources when diesel generators fail, meeting the requirements for black start in the power grid; the ammonia fuel cell is directly connected to the doubly fed motor through an inverter, making black start more reliable.

[0018] 3. The doubly-fed induction motor has two power feeding modes to the ship's power grid. First, when the ammonia-fueled engine operates at a constant speed, the ship can change speeds via variable pitch propellers, and the doubly-fed motor can be directly connected to the ship's power grid. Second, when both the ammonia-fueled engine and the variable-pitch propeller operate at variable speeds, the doubly-fed motor achieves grid connection by adjusting the frequency and phase of synchronous power generation in the rotor excitation windings via a frequency converter. Significant technical advantages can be seen in these two feeding methods. Both methods avoid power losses and rely solely on software control for grid connection. Furthermore, using a small-capacity frequency converter to control the doubly-fed induction motor rotor windings enables variable-speed power generation, improving power generation efficiency and cost. Selecting between these two modes allows for optimal efficiency optimization of the ammonia-fueled engine.

[0019] 4. This invention proposes a marine ammonia-electric hybrid power system with an integrated cooling system. It achieves integrated design of the ammonia-diesel generator and ammonia fuel cell gas path, employing a shared ammonia fuel supply loop to simplify the redundancy of the supply pipeline. Simultaneously, the exhaust gas generated by the fuel cell is introduced into the exhaust pipe of the ammonia-diesel generator, resulting in more efficient waste heat utilization and increased turbine power, which is beneficial for optimizing the performance of the ammonia-diesel generator by increasing compressed air. The exhaust gas recirculation loop design solves the problem of excessive nitrogen oxide emissions from the ammonia-diesel generator, while the cylinder bypass loop prevents compressor surge under partial load.

[0020] 5. Another advantage of the present invention is that by introducing the exhaust gas after the turbine of the ammonia diesel generator into the preheating circuit of the ammonia fuel cell, the cold start of the ammonia fuel cell can be achieved without the need for an additional heat source, thus realizing the reuse of exhaust energy.

[0021] 6. The integrated cooling system designed in this invention utilizes temperature gradients to cool various components of the power system, which can fully realize the gradient utilization of the cooling energy of the cooling system. At the same time, it can rationally design the cooling circuit according to the different cooling water temperature requirements of different components, thereby reducing system redundancy.

[0022] 7. The hybrid power system provided by this system is suitable for the power system of large ocean-going vessels. It can meet the requirements of zero-carbon navigation, ensure low emissions of pollutants such as nitrogen oxides, and guarantee the range of ocean voyages. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the integrated cooling system. Detailed Implementation

[0025] The invention will now be described in more detail with reference to the accompanying drawings:

[0026] Combination Figure 1-2 This invention discloses a marine ammonia-electric hybrid power system with an integrated cooling system, comprising a variable pitch propeller 1, a gearbox 2, a clutch 3, an ammonia engine 4, an ammonia-diesel generator set 5, a doubly-fed induction motor 6, an ammonia fuel cell inverter 7, an ammonia fuel cell 8, a doubly-fed induction motor frequency converter 9, a lithium-ion battery inverter 10, a lithium-ion battery 11, three-way valves 12a, 12b, 12c, 12d, 12e, 12f, 12g, and 12h, an exhaust pipe 13, a turbocharger 14, flow meters 15a, 15b, and 15c, on / off valves 16a and 16b, an ammonia storage tank 17a, an oxygen storage tank 17b, a flame-retardant valve 18, a pressure regulating valve 19, a fuel pump 20a, an exhaust gas recirculation pump 20b, a purification device 21, heat exchangers 22a and 22b, and an intake pipe 23. The connection is as follows: the output of the ammonia fuel engine 4 is mechanically connected to the doubly-fed induction motor 6 and the variable-pitch propeller 1 via the clutch 3 in the gearbox 2; the rotor excitation winding of the doubly-fed induction motor 6 is connected to the output of the ammonia fuel cell 8 via the frequency converter 9, and the stator winding is directly connected to the power grid. The lithium-ion battery 11 is connected to the power grid via the lithium-ion battery inverter 10, the ammonia fuel cell 8 is connected to the power grid via the ammonia fuel cell inverter 7, and the ammonia-diesel generator set 5 is directly connected to the power grid. The ammonia fuel in the ammonia storage tank 17a enters the fuel cell 8 through the first outlet of the three-way valve 12g via the switch shut-off valve 16a, the pressure regulating valve 19, and the flame retardant valve 18. The ammonia gas outlet of the ammonia fuel cell 8 enters the ammonia-diesel generator set 23 via the first outlet of the three-way valve 12h and the fuel flow meter 15c via the fuel pump 20a. The oxygen in the oxygen storage tank 17b enters the ammonia fuel cell 8 via the shut-off valve 16b and the flow meter 15b. A portion of the exhaust gas from the ammonia-diesel generator exhaust pipe 13 enters the ammonia fuel cell via the second outlet of three-way valve 12c and the first outlet of three-way valve 12b. The exhaust gas generated by the ammonia fuel cell 8 and the ammonia-diesel generator 5 are combined into the exhaust pipe 13 via three-way valve 12a. A portion of the exhaust gas from the exhaust pipe 13 passes through the first outlet of three-way valve 12c, the purification device 21, the heat exchanger 22a, the exhaust gas recirculation pump 20b, and then enters the intake pipe via three-way valve 12f; this is the exhaust gas recirculation loop. After being compressed by the turbocharger 14, part of the ambient air enters the exhaust pipe via the second outlet of three-way valve 12e; this is the cylinder bypass loop. Another portion enters the intake pipe 23 via the first outlet of three-way valve 12e, the heat exchanger 22b, and the first outlet of three-way valve 12f. Most of the exhaust gas in the exhaust pipe 13 is discharged into the atmosphere through the turbine in the turbocharger 14. Part of it is discharged directly into the atmosphere through the three-way valve 12d, and the other part enters the fuel cell through the three-way valve 12d and the three-way valve 12b. This is the cold start circuit of the ammonia fuel cell.

[0027] See Figure 2The integrated cooling system includes: seawater pump 24a, freshwater pump 24b, plate heat exchanger 25, pipeline valve bodies 26a, 26b, 26c, 26d, 26e, 26f, 26g, 26h, 26i, 26j, 26k, 26l, 26m, 26n, 26o, 26p, 26q, 26r, 26s, three-way valves 27a, 27b, 27c, 27d, accessory cooling circuit 29, electronic component cooling circuit 30, expansion tank 31, lubricating oil cooling circuit 32, and cylinder liner water cooling circuit 33. The connection is as follows: water pump 24a draws seawater, which passes through valve 26b into plate heat exchanger 25 and then returns to the sea through valve 26a; freshwater is pumped from expansion tank 31 by freshwater pump 24b, passing through three-way valves 27b and 27a, and flow meter 28 to the cooling circuits of various components, with freshwater replenished through valve 26m. The cooling water from water pump 24b is divided into three parts: one part passes through valve bodies 26g and 26h to enter the accessory cooling circuit and electronic component cooling circuit respectively, and flows out through valve bodies 26i and 26j; another part enters the lubricating oil cooling circuit 32 in ammonia diesel generator set 5, and the cooling water from the outlet of lubricating oil cooling circuit 32 is divided into two parts: one part enters cylinder liner water cooling through three-way valve 27c and valve body 26l, and the other part enters the ammonia fuel cell 8 for cooling through three-way valve 27c; the last part of the cooling water from water pump 24b enters the battery 11 for cooling through valve body 26p and flows out through valve body 26q. Finally, the cooling water flowing from the lithium-ion battery 11, the ammonia fuel cell 8, and the cylinder liner water cooling circuit 33 of the ammonia diesel generator 5 is finally collected at the three-way valve 27d, flows through the heat exchanger 25, and then exchanges heat with seawater to form a cycle.

[0028] In this embodiment, the ammonia fuel engine 4 is preferably a compression ignition engine, the ammonia diesel generator set 5 is preferably a spark ignition engine, and the lithium-ion battery 11 is preferably a lithium iron phosphate battery with high power density and small volume and weight.

[0029] The main working modes of this invention are as follows:

[0030] In the ship's standby mode, the start-up mode is initiated by the inverter 9 controlling the doubly-fed induction motor 6 to pull the ammonia fuel engine 4. The power source for the doubly-fed induction motor is directly provided by the ammonia fuel cell 8 controlled by the inverter 7. This setup prevents insufficient power due to ship grid failures and reduces energy loss during power transmission. The ammonia fuel required by the fuel cell in the grid enters the ammonia fuel cell through the ammonia storage tank 17a, shut-off valve 16a, pressure regulating valve 19, flame retardant valve 18, three-way valve 12g, and flow meter 15a. It should be noted that in cold environments, the ammonia-diesel generator unit 5 starts first. A portion of the exhaust gas produced by the exhaust pipe 13 enters the ammonia fuel cell for preheating through three-way valves 12d, 12b, or 12c. After the fuel cell has been preheated to a suitable temperature, it starts up.

[0031] In mechanical mode, clutch 3 is engaged, at which time doubly fed induction motor 6 is not working, and ammonia fuel engine 4 drives variable pitch propeller 1 through gearbox 2.

[0032] In electric propulsion mode, the doubly-fed induction motor 6 starts, the clutch 3 disengages, and the ammonia engine 4 stops operating. The variable-pitch propeller 1 is driven by the doubly-fed induction motor 6. At this time, the speed ratio of the gearbox 2 can be selected according to the ship's speed and pitch ratio. The control rule is as follows: when the ship's speed is low, the gearbox 2 selects a high speed ratio gear; when the ship's speed is high, a low speed ratio gear is selected. When the ship is docked or berthed, the pitch of the variable-pitch propeller 1 is reduced to meet the speed range of the doubly-fed induction motor 6, and the speed ratio of the gearbox 2 should also be selected at a high speed ratio.

[0033] In the hybrid propulsion mode, clutch 3 engages, and the doubly-fed induction motor 6 and the ammonia fuel engine 4 jointly drive the variable-pitch propeller 1 via gearbox 2. In this mode, the doubly-fed induction motor 6 is controlled by the ship's electrical network via frequency converter 9. In this mode, the ammonia fuel engine 4 can operate in constant power mode or optimal economic curve mode, and the engine operating range is optimized by adjusting the pitch ratio of the variable-pitch propeller 1 and the speed of the doubly-fed induction motor.

[0034] In power generation mode, clutch 3 engages, and part of the power from ammonia fuel engine 4 drives doubly-fed induction motor 6 to generate electricity, while another part of the power drives variable-pitch propeller 1 through gearbox 2. At this time, the doubly-fed induction motor can feed power to the grid in two ways: when adjusting the pitch ratio of variable-pitch propeller 1 to make the speed of ammonia engine 4 reach the rated speed and generate 50Hz frequency power, it directly feeds power to the ship's power grid. At this time, frequency converter 9 does not work, and doubly-fed induction motor 6 can act as an asynchronous motor; when the speed of doubly-fed induction motor 6 is less than the rated speed, it feeds power to the ship's power grid through variable-voltage frequency converter 9.

[0035] The ship's electrical grid system includes an ammonia-diesel generator set (5), an ammonia fuel cell (8), and a lithium-ion battery (11). Its main operating modes are divided into individual operating mode and combined operating mode.

[0036] In standalone mode, the ammonia-diesel generator 5, ammonia fuel cell 8, or lithium-ion battery 11 supply power to the ship's power grid independently, based on the power demand of the ship's power grid. In joint operation mode, when the ship's power demand exceeds that of one of the generators, the two or three generators supply power together, and the power output of each generator is optimized according to the energy management strategy.

Claims

1. A marine ammonia-electric hybrid power system with an integrated cooling system, characterized in that: The system includes a variable-pitch propeller, an ammonia engine, an ammonia-diesel generator set, a doubly-fed induction motor, an ammonia fuel cell, a lithium-ion battery, a power grid, an ammonia storage tank, an oxygen storage tank, and a comprehensive cooling system. The ammonia engine is connected to the doubly-fed induction motor and the variable-pitch propeller via a clutch. The rotor excitation winding of the doubly-fed induction motor is connected to the output of the ammonia fuel cell via a doubly-fed induction motor inverter. The stator winding of the doubly-fed induction motor is connected to the power grid. The lithium-ion battery is connected to the power grid via a lithium-ion battery inverter, and the ammonia fuel cell is connected to the power grid via an ammonia fuel cell inverter. The ammonia-diesel generator set is directly connected to the power grid. The ammonia storage tank is connected to the ammonia fuel cell via a first shut-off valve, a pressure regulating valve, a flame-retardant valve, and the first outlet of a seventh three-way valve. The ammonia outlet of the ammonia fuel cell is connected to the ammonia-diesel generator set via a first fuel pump, the first outlet of an eighth three-way valve, and a second flow meter. The deaerator tank is connected to the ammonia fuel cell via a second shut-off valve and a second flow meter. A portion of the exhaust gas from the diesel generator set's exhaust pipe enters the ammonia fuel cell via the second outlet of the third three-way valve and the first outlet of the second three-way valve. The exhaust gas generated by the ammonia fuel cell and the exhaust gas generated by the ammonia diesel generator set are combined via a three-way valve into the exhaust pipe of the ammonia diesel generator set. A portion of the exhaust gas in the exhaust pipe passes through the first outlet of the third three-way valve, the purification device, the first heat exchanger, and the second exhaust gas recirculation pump, and then enters the intake pipe of the ammonia diesel generator set via the sixth three-way valve. After the air is compressed by the turbocharger of the ammonia diesel generator set, a portion enters the exhaust pipe through the second outlet of the fifth three-way valve, and a portion enters the intake pipe through the first outlet of the fifth three-way valve, the second heat exchanger, and the first outlet of the sixth three-way valve. The exhaust gas in the exhaust pipe is discharged into the atmosphere via the turbine, a portion is directly discharged into the atmosphere via the fourth three-way valve, and another portion enters the ammonia fuel cell via the fourth three-way valve and the second three-way valve. The integrated cooling system includes a seawater pump, a freshwater pump, a plate heat exchanger, and an expansion tank. The seawater pump draws seawater through the second valve body into the plate heat exchanger, and then returns to the sea through the first valve body. The freshwater pump pumps freshwater from the expansion tank, which is divided into three parts after passing through the thirteenth-way valve, the ninth-way valve, and a flow meter. The first part passes through the seventh and eighth valve bodies to enter the accessory cooling circuit and the electronic device cooling circuit, respectively, and flows out through the ninth and tenth valve bodies. The second part enters the lubricating oil cooling circuit of the ammonia diesel generator set, and is divided into two paths at the outlet of the lubricating oil cooling circuit. The first path enters the cylinder liner water cooling circuit through the eleventh-way valve and the twelfth valve body, and the second path enters the ammonia fuel cell through the eleventh-way valve. The third part enters the lithium-ion battery through the sixteenth valve body and flows out through the seventeenth valve body. The cooling water flowing out from the lithium-ion battery, the ammonia fuel cell, and the cylinder liner water cooling circuit of the ammonia diesel generator set is collected at the twelfth-way valve, flows through the heat exchanger, and then exchanges heat with the seawater.

2. A marine ammonia-electric hybrid power system with an integrated cooling system according to claim 1, characterized in that: In startup mode, the inverter controls the doubly-fed induction motor to drive the ammonia engine to start. The power source for the doubly-fed induction motor is directly provided by the ammonia fuel cell controlled by the inverter. The ammonia fuel required by the fuel cell in the grid enters the ammonia fuel cell through the ammonia storage tank, the first shut-off valve, the pressure regulating valve, the flame retardant valve, the seventh three-way valve, and the first flow meter. In cold environments, the ammonia diesel generator unit starts first. A portion of the exhaust gas produced by the exhaust pipe enters the ammonia fuel cell for preheating through the fourth three-way valve, the second three-way valve, or the third three-way valve. After the fuel cell is preheated to the preset temperature, the ammonia fuel cell starts.

3. A marine ammonia-electric hybrid power system with an integrated cooling system according to claim 1, characterized in that: In mechanical mode, the clutch engages, the doubly fed induction motor does not operate, and the ammonia fuel engine drives the variable pitch propeller through the gearbox.

4. A marine ammonia-electric hybrid power system with an integrated cooling system according to claim 1, characterized in that: In electric propulsion mode, the doubly-fed induction motor starts, the clutch disengages, the ammonia engine stops working, and the variable-pitch propeller is driven by the doubly-fed induction motor. When the ship's speed is low, the gearbox selects a high speed ratio gear, and when the ship's speed is high, the gearbox selects a low speed ratio gear. When the ship is docked or berthed, the pitch of the variable-pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the gearbox speed ratio is selected at a high speed ratio gear.

5. A marine ammonia-electric hybrid power system with an integrated cooling system according to claim 1, characterized in that: In hybrid propulsion mode, the clutch engages, and the doubly fed induction motor and the ammonia fuel engine jointly drive the variable pitch propeller via a gearbox. The doubly fed induction motor is controlled by the ship's electrical network via a frequency converter, and the ammonia fuel engine operates in constant power mode or optimal economic curve mode. The engine's operating range is optimized by adjusting the variable pitch propeller pitch ratio and the speed of the doubly fed induction motor.

6. A marine ammonia-electric hybrid power system with an integrated cooling system according to claim 1, characterized in that: In power generation mode, the clutch engages, and part of the power from the ammonia fuel engine drives the doubly-fed induction motor to generate electricity, while another part of the power drives the variable-pitch propeller through the gearbox. The doubly-fed induction motor feeds power to the grid in two ways: when the ammonia engine speed is adjusted to the rated speed by adjusting the variable-pitch propeller pitch ratio to generate 50Hz frequency power, it directly feeds power to the ship's power grid. At this time, the frequency converter does not work, and the doubly-fed induction motor acts as an asynchronous motor; when the speed of the doubly-fed induction motor is less than the rated speed, it feeds power to the ship's power grid through a variable-voltage frequency converter.

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