Ammonia fuel combined supply system coupling hydrogen production and Kalina cycle and operation method

Abstract

The invention discloses a hydrogen production and Kalina cycle coupled ammonia fuel combined supply system and an operation method, and relates to the technical field of ammonia fuel power of ship and ocean engineering platforms. Comprising an ammonia fuel supply unit, a combustion reaction unit, a Kalina circulation unit, an ammonia decomposition reactor, a flue gas distribution control unit, a cryogenic recovery branch and a phase change energy storage device. High-temperature flue gas is sequentially subjected to ammonia decomposition, Kalina cycle power generation and liquid ammonia gasification energy supply through three series branches, and gradient utilization of heat energy is achieved. The cryogenic recovery branch constructs a closed ammonia working medium cycle, and liquid ammonia cools a Kalina cycle working medium and is heated by itself and supplied by branches; the fuel injection system adopts hydrogen-ammonia double direct injection sequential control, and an electronic control unit dynamically adjusts the hydrogen doping ratio. According to the invention, synergistic coupling of chemical energy and physical energy is realized, comprehensive energy efficiency is remarkably improved, combustion stability is improved, unburned ammonia emission is reduced, operation safety is guaranteed through a triple safety protection system, and an efficient and safe solution is provided for zero-carbon power.

Description

Technical Field

[0001] This invention relates to the field of ammonia fuel power systems on ships and marine engineering platforms, specifically to an ammonia fuel cogeneration system coupled with hydrogen production and the Karina cycle, and its operation method. Background Technology

[0002] The application of zero-carbon energy in ship propulsion, offshore engineering platforms, and distributed power generation has become a focus of the industry. Ammonia fuel, with its high hydrogen content, ease of liquefaction, storage, and transportation, and its ability to be produced from renewable energy sources, is considered a highly promising zero-carbon alternative fuel. However, ammonia fuel still faces many technical bottlenecks in practical applications. Existing ammonia fuel power systems have significant shortcomings in energy utilization, combustion stability, safety, and adaptability to special operating conditions, hindering its large-scale promotion.

[0003] In terms of energy utilization, existing technologies generally suffer from low energy efficiency and severe grade mismatch. Prior art document (CN202511010972.3) discloses a system for the coupled utilization of ammonia fuel waste heat and a Karina cycle. This system, through the coupling of an ammonia fuel supply system and a Karina cycle system, realizes the utilization of liquid ammonia cold energy, the supply and return of liquid cold heat energy, and flue gas heat energy. However, this system is limited to energy recovery at the physical cycle level and does not involve chemical energy conversion processes. Its energy utilization method is relatively simple, only converting waste heat into electrical energy through the Karina cycle, failing to couple high-temperature flue gas heat energy with the ammonia decomposition hydrogen production reaction. This results in the incomplete utilization of the grade advantage of the high-temperature heat energy, limiting the overall energy efficiency improvement of the system.

[0004] Prior art document (CN202411025112.2) discloses an ammonia-hydrogen combustion-ammonia decomposition hydrogen production-fuel cell coupling system. This system achieves cascaded energy utilization by coupling ammonia decomposition hydrogen production with fuel cell power generation. However, this system is mainly applicable to distributed power generation scenarios and is not designed for the special operating conditions of ships and marine engineering platforms. It uses the burner's exhaust gas to heat the ammonia decomposition reaction, and the combustion products are directly emitted, failing to form a closed loop with the waste heat recovery of the power system, resulting in significant energy waste. Furthermore, this system does not involve the Kalina cycle, and the waste heat in the medium and low temperature range is not effectively utilized. At the same time, it lacks consideration for the high power output, variable load adaptability, and space compactness requirements of ship power systems, making it difficult to directly apply to ship main propulsion systems.

[0005] In addition to the shortcomings of the aforementioned comparative documents, existing technologies also face the following common problems: First, poor combustion stability and insufficient safety of external mixing. Pure ammonia fuel has a low laminar flame velocity and a long ignition delay, leading to easy misfire at low speeds and easy detonation at high speeds. Existing technologies mostly use external premixed hydrogen to improve combustion performance, but this method will form a persistent combustible gas mixture in the burner or pipeline, posing significant safety risks. Furthermore, external mixing is difficult to precisely control the in-cylinder mixing process, which can easily lead to combustion failure and serious exceedances of unburned ammonia emissions, making it difficult to meet international maritime environmental regulations. Second, poor adaptability to special ship operating conditions. On ammonia-fueled ships, liquid ammonia is directly injected into the main engine cylinder at high pressure for combustion, requiring the installation of return pipes and overpressure relief pipes; the high toxicity of ammonia and the risk of explosion after leakage necessitate the installation of strict ammonia capture facilities. Existing technologies fail to effectively coordinate the high-grade thermal energy (temperatures exceeding 400°C) of the flue gas after combustion with the high-grade cold energy (storage temperature -33°C) of the liquid ammonia storage tank, resulting in energy waste and increased power consumption of auxiliary systems. Furthermore, existing Karina cycles primarily utilize seawater systems for cooling and heat exchange. Contact between seawater and ammonia can easily lead to safety risks such as working fluid dilution, pipeline freezing, and toxic leaks, making them unsuitable for the special environments of ships with limited engine room space and stringent explosion-proof requirements.

[0006] Third, the energy cascade utilization lacks a closed-loop design. Existing waste heat utilization technologies mostly utilize single or partial levels, failing to achieve full-process cascade matching based on energy grade differences. Heat from the high-temperature stage is not used to drive chemical reforming reactions, and irreversible heat transfer losses occur in the medium- and low-temperature stages, making it difficult to overcome bottlenecks in overall system energy efficiency. Simultaneously, the control strategies of existing systems are relatively simple, failing to dynamically adjust energy distribution and fuel blending ratios according to load changes, resulting in poor stability and energy efficiency under variable load conditions.

[0007] Therefore, developing an ammonia fuel power system capable of precise energy quality matching, stable and safe combustion, and adaptability to the special operating conditions of ships has become a pressing technical problem for the industry. This invention, by coupling hydrogen production with the Karina cycle, constructs a cascaded utilization architecture for synergistic chemical and physical energy utilization. Combined with in-cylinder direct injection stratified combustion and cryogenic recovery design, it aims to overcome many shortcomings of existing technologies and provide a highly efficient, clean, and safe zero-carbon power solution for ships and marine engineering platforms. Summary of the Invention

[0008] The present invention aims to overcome at least one of the defects of the prior art mentioned above, and provides an ammonia fuel cogeneration system and operation method that couples hydrogen production and the Karina cycle, so as to achieve precise matching and cascade utilization of energy grade, improve combustion stability and safety, reduce emission risks, and adapt to the special operating conditions of ships and marine engineering platforms.

[0009] The ammonia fuel supply unit of this invention serves as the core of the system's fuel supply, comprising a liquid ammonia storage tank and a main gasification heat exchanger. The liquid ammonia storage tank stores high-pressure liquid ammonia, while the main gasification heat exchanger handles the gasification of low-pressure liquid ammonia. Together, they provide a continuous and stable source of ammonia for subsequent combustion and hydrogen production processes. The combustion reaction unit generates high-temperature flue gas at a temperature not lower than 400°C by burning ammonia-hydrogen mixed fuel, laying the foundation for the cascaded energy utilization of the entire system. The Karina cycle unit focuses on capturing the heat in the mid-temperature range of 120-420°C from the high-temperature flue gas, driving the turbine to convert thermal energy into electrical energy. The ammonia decomposition reactor utilizes the heat from the high-temperature flue gas to decompose part of the ammonia fuel into hydrogen and nitrogen. The decomposition rate can be flexibly adjusted according to operating conditions, supplementing the combustion reaction unit with hydrogen to improve combustion performance. The flue gas distribution and control unit plays a crucial role in regulating the flow direction of the flue gas from the combustion reaction unit, while simultaneously reducing unburned ammonia emissions in the flue gas to a safe concentration, ensuring the environmentally friendly operation of the system. This core architecture forms the foundation for fuel supply, energy conversion, and emission control, ensuring efficient operation in the future.

[0010] The flue gas distribution control unit of this invention is further refined into three series-connected branches: a high-temperature reforming branch, a medium-temperature driving branch, and a low-temperature gasification branch. The high-temperature flue gas generated by the combustion reaction unit flows sequentially through these three branches, achieving cascaded utilization of thermal energy. The high-temperature reforming branch guides the high-temperature flue gas into the ammonia decomposition reactor, providing sufficient heat for the ammonia decomposition reaction. The medium-temperature driving branch guides the flue gas after the ammonia decomposition reactor into the Karina circulation unit, driving the ammonia-water working fluid to generate steam, thereby promoting the power generation process. The low-temperature gasification branch guides the subsequent flue gas into the main gasification heat exchanger, providing the necessary heat for liquid ammonia gasification. This series-connected branch design ensures full utilization of flue gas at different temperatures and grades, avoiding thermal energy waste and significantly improving the system's efficiency in recovering flue gas thermal energy.

[0011] The system incorporates a cryogenic recovery branch. After liquid ammonia flows from the storage tank, it passes through the Karina circulation unit, where its internal working fluid is cooled. During this process, the liquid ammonia itself is heated. The heated liquid ammonia is then divided into two streams. The first stream, accounting for 50-90% of the total flow, enters the combustion reaction unit through a first pipeline and is directly injected into the cylinder in liquid form to participate in combustion. The second stream, accounting for 10-50% of the total flow, enters the main gasification heat exchanger through a second pipeline and, after gasification, enters the ammonia decomposition reactor to participate in the decomposition reaction. The cryogenic recovery branch design creates a closed ammonia working fluid cycle, achieving both the recovery and utilization of the liquid ammonia's cold energy and preventing direct contact between ammonia and the external environment, reducing the risk of ammonia leakage. Simultaneously, the reasonable flow distribution meets the dual requirements of combustion and hydrogen production.

[0012] The flue gas distribution control unit, based on three series branches, is also equipped with an exhaust pipe, a first flue gas temperature sensor, a second flue gas temperature sensor, a flue gas logic control unit, and third, fourth, and fifth valves. The fourth valve is installed on the exhaust pipe to control the flue gas flow rate. The input end of the high-temperature reforming branch is connected to the exhaust pipe, and the output end is connected to the ammonia decomposition reactor. The third valve and the first flue gas temperature sensor are sequentially installed on the high-temperature reforming branch, respectively responsible for controlling the flue gas flow rate and monitoring the flue gas temperature. The input end of the medium-temperature drive branch is connected to the flue gas outlet of the ammonia decomposition reactor, and the output end is connected to the second heat exchanger, enabling relay power supply of the flue gas. The input end of the low-temperature gasification branch is connected to the flue gas outlet of the second heat exchanger, and the output end is connected to the main gasification heat exchanger. The second flue gas temperature sensor is installed on the low-temperature gasification branch to monitor the flue gas temperature in real time. A fifth valve is installed on the first branch, with its input end connected to the flue gas outlet of the main gasification heat exchanger and its output end connected to the exhaust pipe, forming a complete flue gas emission loop. The flue gas logic control unit can precisely adjust the opening degrees of the third, fourth, and fifth valves based on the combustion load and hydrogen blending ratio requirements of the combustion reaction unit. This changes the flow distribution ratio between the exhaust pipe and the high-temperature reforming branch, thereby regulating the hydrogen production (i.e., the decomposition rate) of the ammonia decomposition reactor and ensuring that the hydrogen volume ratio in the ammonia-hydrogen mixed fuel remains stable within a reasonable range of 5%-20%. This intelligent control design allows the system to flexibly adjust according to actual operating conditions, ensuring combustion stability and energy utilization efficiency.

[0013] The combustion reaction unit consists of an ammonia-fueled internal combustion engine and a fuel injection system. The fuel injection system includes a liquid ammonia direct injection system, a hydrogen direct injection system, and an electronic control unit. The liquid ammonia direct injection system includes a high-pressure ammonia pump and a liquid ammonia direct injector. The high-pressure ammonia pump is installed on the first pipeline. The cryogenic recovery branch is branched off to the first pipeline after passing through the condenser. The output end of the first pipeline is connected to the liquid ammonia direct injector to provide it with high-pressure liquid ammonia. The hydrogen direct injection system consists of a hydrogen supply device and a hydrogen direct injector, which are connected by a hydrogen pipeline to ensure a stable hydrogen supply. The liquid ammonia direct injector and the hydrogen direct injector are respectively connected to the cylinders of the ammonia-fueled internal combustion engine. The electronic control unit is configured to control the opening timing of the hydrogen direct injector and the liquid ammonia direct injector at different phases of the engine's compression stroke, and dynamically adjust the hydrogen-ammonia injection ratio according to the real-time operating conditions of the internal combustion engine, thereby achieving stratified combustion within the internal combustion engine cylinders. This dual direct injection and precise control design solves the problem of poor combustion stability of pure ammonia. The guiding combustion effect of hydrogen shortens the ignition delay period, the stratified combustion mode improves combustion efficiency, and at the same time reduces unburned ammonia emissions.

[0014] The fuel injection system supports closed-loop feedback correction, and its operating parameters have been optimized. Regarding pressure settings, the high-pressure ammonia pump pressurizes liquid ammonia to at least 50 bar, while the hydrogen supply unit maintains the hydrogen rail pressure between 5 and 20 bar, ensuring the injection pressure meets combustion requirements. For phase settings, the electronic control unit controls the hydrogen direct injector to begin injection within the 30%-50% phase of the compression stroke and the liquid ammonia direct injector to begin injection within the 90%-95% phase of the compression stroke, strictly ensuring that hydrogen injection ends before ammonia injection begins, allowing sufficient time for complete combustion of the ammonia fuel. Regarding accuracy settings, the electronic control unit achieves a steady-state deviation of no more than ±5% and a transient deviation of no more than ±10% in controlling the hydrogen blending volume ratio. These optimized operating parameters and closed-loop feedback correction function further improve the accuracy of fuel injection and the stability of the combustion process, ensuring the system maintains good combustion performance under different operating conditions.

[0015] The electrical energy generated by the Karina cycle unit is stored through a phase change energy storage device (PVC). This PVC consists of two stages: a high-temperature stage (400-600℃) and a medium-temperature stage (100-200℃), connected to the ammonia decomposition reactor and the main gasification heat exchanger, respectively. When the inlet temperature of the high-temperature reforming branch is detected by the flue gas temperature sensor as below or equal to 400℃, the PVC releases the latent heat from the high-temperature stage to supplement heating for the ammonia decomposition reactor. When the inlet temperature of the low-temperature gasification branch is detected by the flue gas temperature sensor as below or equal to 180℃, the PVC releases the latent heat from the medium-temperature stage to supplement heating for the main gasification heat exchanger, forming a closed loop for electrical energy utilization. Simultaneously, the gasification cooling capacity can be calculated in real time using the inlet and outlet temperature difference of the main gasification heat exchanger and the liquid ammonia flow rate, providing data support for system control. The PVC solves the problem of insufficient heat under varying operating conditions, ensuring the stable operation of the ammonia decomposition reactor and the main gasification heat exchanger, and improving the system's adaptability to load changes.

[0016] The Karina cycle unit consists of a condenser, a first booster pump, a first heat exchanger, a second heat exchanger, a separator, a mixer, a steam turbine, and a generator. The ammonia solution output from the mixer first flows through the condenser for cooling, then is pressurized by the first booster pump, heated by the first and second heat exchangers, and finally enters the separator. High-temperature, pressurized ammonia vapor is separated from the upper layer of the separator. This vapor enters the steam turbine, driving it to perform work, which in turn drives the generator to produce electricity. The electricity generated by the generator is transmitted via electrical connections to a phase change energy storage device for storage and to supply end users. The solution returning from the bottom of the separator and the exhaust gas from the steam turbine outlet mix in the mixer to form a new ammonia solution, which re-enters the cycle. The components of the Karina cycle unit work together to form a complete energy conversion cycle, efficiently converting the heat in the flue gas into electrical energy, providing additional electrical output to the system and improving overall energy recovery efficiency. The ammonia solution entering the separator has a pressure of 4-55 bar, a temperature of 120-400℃, and a concentration of 20%-90%.

[0017] The combustion reaction unit also includes a return pipe, and the fuel injection system also includes an oxygen sensor and a cylinder pressure sensor; the input end of the return pipe is connected to the liquid ammonia direct injector, and the output end is connected to the liquid ammonia storage tank; the oxygen sensor and the cylinder pressure sensor are located on the cylinder of the internal combustion engine. The main gasification heat exchanger is an ammonia-resistant plate heat exchanger, with plates made of 316L stainless steel or Ni-Cr corrosion-resistant alloy, wherein the Ni content is ≥35%, the plate thickness is 0.5-1.0 mm, and the design pressure is ≥2.5 MPa; or it is an immersed coil heat exchanger, with the coil placed inside the liquid ammonia storage tank, the coil outer diameter is ≥20 mm, and the wall thickness is ≥2 mm; the reaction side outlet of the ammonia decomposition reactor is equipped with a three-stage temperature interlock protection device and a hydrogen concentration detector to prevent catalyst sintering and loss of activity and to feed back the hydrogen volume concentration signal to the flue gas distribution control unit to adjust the decomposition rate; the combustion reaction unit is an ammonia fuel two-stroke low-speed internal combustion engine with a power range of 5-20 MW; or it is a gas turbine with an exhaust temperature of 500-600℃.

[0018] This invention also provides an operating method for the above-mentioned ammonia fuel cogeneration system coupled with hydrogen production and the Karina cycle, the method comprising the following steps: S1: Liquid ammonia flows out from the liquid ammonia storage tank and passes through the condenser of the Karina cycle unit, where it is heated while cooling the Karina cycle working fluid; S2: The heated liquid ammonia is divided into two streams, with 50% to 90% of the flow entering the main stream and being injected into the ammonia fuel internal combustion engine in liquid form through the fuel injection system, and 10% to 50% of the flow entering the branch stream, where it is vaporized by the main gasification heat exchanger and then enters the ammonia decomposition reactor; S3: A portion of the high-temperature flue gas generated by the combustion of the ammonia fuel internal combustion engine flows through a high-temperature reformer. The system consists of three branches: S1, S2, and S3, S4. The hydrogen produced in the third step and the liquid ammonia from the main circuit in the second step are injected into the cylinders of an ammonia-fueled internal combustion engine through independent fuel injection systems. During the compression stroke, in-cylinder mixing and combustion are achieved, continuously generating high-temperature flue gas. S5. The high-temperature flue gas generated in the ammonia-fueled internal combustion engine in the third and fourth steps flows sequentially through a high-temperature reforming branch to drive ammonia decomposition for hydrogen production, a medium-temperature driving branch to drive the Karina cycle power generation, and a low-temperature gasification branch to supply energy for liquid ammonia gasification. This operating method has a clear logic, with each step closely linked, fully leveraging the synergistic effect of each unit to maximize the cascade utilization and efficient conversion of energy.

[0019] The in-cylinder mixing injection method in step four of the operation method employs a precise timing control strategy. Hydrogen-guided injection occurs during the 30%-50% phase of the compression stroke, where the injected hydrogen forms a lean mixture, providing a guiding flame for subsequent combustion. The main ammonia fuel injection is implemented during the 90%-95% phase of the compression stroke, injecting liquid ammonia at a pressure of no less than 50 bar, using the flame formed by hydrogen combustion to ignite the liquid ammonia. The hydrogen volume ratio in the ammonia-hydrogen mixture is controlled at 5%-20%, and the hydrogen-guided injection ends before the main ammonia fuel injection begins. This timing design ensures thorough mixing of hydrogen to form a uniform guiding flame, effectively solving the problems of difficult ignition and slow combustion speed of pure ammonia, significantly improving combustion stability, reducing combustion cycle variability, and simultaneously reducing emissions of unburned ammonia and nitrogen oxides.

[0020] The regulation of the hydrogen blending volume ratio in ammonia-hydrogen blended fuel is executed by the electronic control unit (ECU), specifically in three steps: T1: Target determination. The ECU, based on engine speed and load, queries a 3D MAP (Modular Mapping) and determines a hydrogen blending volume ratio target of 5%-20%, prioritizing combustion stability and minimizing unburned ammonia emissions. T2: Pulse width calculation. Based on the hydrogen rail pressure (PH2) and temperature (TH2), and corrected using the state equation, the hydrogen pulse width is calculated using the flow pulse spectrum. Simultaneously, based on the liquid ammonia rail pressure (PNH3), the liquid ammonia pulse width is calculated using the flow pulse spectrum. T3: Closed-loop correction. The ECU, based on exhaust oxygen concentration or cylinder pressure signals, back-calculates the actual hydrogen blending ratio and dynamically corrects the pulse width using a PID or MPC controller, ensuring that the steady-state deviation of the hydrogen blending volume ratio does not exceed ±5%, and the transient deviation does not exceed ±10%. This precise regulation strategy ensures optimal matching of the hydrogen blending volume ratio under different operating conditions, consistently maintaining good combustion performance and improving the system's adaptability and operational stability under varying operating conditions.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Breaking through traditional energy efficiency bottlenecks and realizing cross-dimensional energy synergy: The innovative construction of a four-level series energy cascade utilization architecture of "high temperature hydrogen production - medium temperature power generation - low temperature gasification - cryogenic recovery" deeply couples chemical energy conversion with physical cycle, breaking through the limitation of traditional ammonia fuel system only utilizing a single energy form; the flue gas series branch is equipped with multi-level temperature interlock protection and intelligent flow control to ensure that each unit always operates in the specified temperature range; the Karina cycle efficiently captures medium temperature waste heat and converts it into electrical energy; the cryogenic recovery branch realizes the precise replacement of liquid ammonia cold energy and circulating working fluid heat energy; compared with the traditional ammonia fuel power system, the overall energy efficiency is significantly improved.

[0022] (2) Innovation in combustion mechanism, achieving a dual breakthrough in environmental protection and stability: The hydrogen-ammonia in-cylinder stratified direct injection guided combustion technology is proposed. By controlling the timing of early hydrogen injection to form a uniform guiding flame and late liquid ammonia injection for precise ignition, the industry pain points of low laminar flame velocity and long ignition delay of pure ammonia are fundamentally solved. The laminar flame velocity is significantly improved, the combustion cycle variation rate is stably controlled at an extremely low level, and the emissions of unburned ammonia and N2O are greatly reduced.

[0023] (3) Safety design closed loop, adaptable to harsh working conditions: Construct a triple safety protection system of "instantaneous mixing - closed loop - interlock protection". The in-cylinder instantaneous mixing strategy eliminates the explosion risk of continuous combustible gas mixture in the pipeline; the closed ammonia working fluid circulation design blocks the ammonia leakage path from the source; and meets the explosion protection specifications of the classification society and the special working conditions of limited space in the ship's engine room and strict explosion protection requirements.

[0024] (4) Optimization of life cycle value, highlighting the dual advantages of economy and operation and maintenance: The cryogenic recovery branch uses liquid ammonia cryogenic energy to replace traditional seawater cooling or mechanical refrigeration, avoiding operation and maintenance risks such as seawater pollution and pipeline freezing, while saving a lot of auxiliary system power consumption; the phase change energy storage device realizes cross-time optimization of electrical energy and thermal energy, significantly reducing operating costs. The system adopts a modular (four major modules: ammonia fuel supply unit, Karina circulation unit, ammonia decomposition reactor, and flue gas distribution control unit) integrated design, with a compact structure and strong compatibility of key components, reducing equipment space occupation and maintenance nodes, significantly extending the maintenance cycle, and significantly optimizing the life cycle cost compared with traditional solutions, achieving a synergistic improvement in energy efficiency, safety and environmental performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the ammonia fuel cogeneration system coupled with hydrogen production and the Karina cycle, provided in an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of a fuel injection system provided in an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the hydrogen doping injection process provided in an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached drawings: 100-Ammonia fuel supply unit; 101-Liquid ammonia storage tank; 103-Separator; 104-Hydrogen supply device; 106-First booster pump; 111-First heat exchanger; 112-Second heat exchanger; 113-Main gasification heat exchanger; 119-Condenser; 120-Steam turbine; 121-Mixer; 122-Generator; 131-First valve; 132-Second valve; 133-Third valve; 134-Fourth valve; 135-Fifth valve; 137-First flue gas temperature sensor; 138-Second flue gas temperature sensor; 139-Throttle valve; 141-High-temperature reforming branch; 142-Medium-temperature drive branch; 143-Low-temperature gasification branch; 144-First pipe 145-Second Pipeline; 146-First Branch Pipe; 148-Oxygen Sensor; 149-Cylinder Pressure Sensor; 150-Spark Plug; 200-Combustion Reaction Unit; 201-Cryogenic Recovery Branch Line; 202-Return Liquid Pipe; 203-Ammonia Pipe; 213-Electronic Control Unit; 204-Exhaust Pipe; 205-Steam Pipe; 206-Hydrogen Tank; 207-Liquid Ammonia Direct Injector; 208-Hydrogen Direct Injector; 209-High Pressure Ammonia Pump; 210-Fuel Injection System; 211-Liquid Ammonia Direct Injection System; 212-Hydrogen Direct Injection System; 300-Karina Circulation Unit; 400-Ammonia Decomposition Reactor; 500-Flue Gas Distribution Control Unit; 501-Flue Gas Logic Control Unit; 600-Phase Change Energy Storage Device. Detailed Implementation

[0029] The accompanying drawings illustrate the technical solutions of the embodiments of the present invention in more detail. Throughout the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0031] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0032] Example 1

[0033] This embodiment provides an ammonia fuel cogeneration system that couples hydrogen production with the Karina cycle, such as Figures 1-2 As shown, it includes: The ammonia fuel supply unit 100 includes a liquid ammonia storage tank 101 and a main gasification heat exchanger 113, used to provide a high-pressure liquid ammonia source and low-pressure gasified ammonia gas; the main gasification heat exchanger 113 is an ammonia corrosion resistant plate heat exchanger, the plate material is 316L stainless steel or Ni-Cr corrosion resistant alloy, wherein the Ni content is ≥35%, the plate thickness is 0.5-1.0mm, and the design pressure is ≥2.5MPa; or it is an immersed coil heat exchanger, the coil is placed inside the liquid ammonia storage tank 101, the outer diameter of the coil is ≥20mm, and the wall thickness is ≥2mm; Combustion reaction unit 200 is used to burn ammonia-hydrogen mixed fuel and generate high-temperature flue gas, the temperature of which is ≥400℃; the combustion reaction unit 200 includes an ammonia fuel internal combustion engine and a fuel injection system 210; the ammonia fuel internal combustion engine is an ammonia fuel two-stroke low-speed internal combustion engine with a power range of 5-20MW; or a gas turbine with an exhaust temperature of 500-600℃. The fuel injection system (210) includes: a liquid ammonia direct injection system (211): including a high-pressure ammonia pump (209) and a liquid ammonia direct injector (207), the high-pressure ammonia pump (209) is located on the first pipeline (144), the cryogenic recovery branch (201) is branched to the first pipeline (144) after passing through the condenser (119), and the output end of the first pipeline (144) is connected to the liquid ammonia direct injector (207); a hydrogen direct injection system (212): including a hydrogen supply device (1 04) Hydrogen direct injector (208), which is connected to the hydrogen pipe (206); the liquid ammonia direct injector (207) and the hydrogen direct injector (208) are respectively connected to the cylinder of the ammonia fuel internal combustion engine; the electronic control unit (213) is configured to control the opening of the hydrogen direct injector (208) and the liquid ammonia direct injector (207) at different phases of the engine compression stroke, and dynamically adjust the hydrogen / ammonia injection ratio according to the internal combustion engine operating conditions to achieve stratified combustion in the internal combustion engine cylinder.

[0034] The fuel injection system supports closed-loop feedback correction, and its operating parameters are as follows: Pressure setting: The high-pressure ammonia pump pressurizes liquid ammonia to ≥50 bar, and the hydrogen supply device maintains the hydrogen rail pressure at 5-20 bar; Phase setting: The electronic control unit (213) controls the hydrogen direct injector to start injection within the 30%-50% phase of the compression stroke, and controls the liquid ammonia direct injector to start injection within the 90%-95% phase of the compression stroke, and ensures that the hydrogen injection ends before the ammonia injection begins. Accuracy setting: The control accuracy of the electronic control unit (213) for the hydrogen blending volume ratio is: steady-state deviation ≤ ±5%, transient deviation ≤ ±10%. The fuel injection system 210 also includes an oxygen sensor 148 and a cylinder pressure sensor 149; the input end of the return pipe 202 is connected to the liquid ammonia direct injector 207, and the output end is connected to the liquid ammonia storage tank 101; the oxygen sensor 148 and the cylinder pressure sensor 149 are located on the internal combustion engine cylinder.

[0035] The Karina cycle unit 300 is used to drive the steam turbine 120 to generate electricity using the intermediate-temperature heat in the high-temperature flue gas, wherein the temperature range of the intermediate-temperature heat is 120-420℃. The Karina cycle unit 300 includes a condenser 119, a first booster pump 106, a first heat exchanger 111, a second heat exchanger 112, a separator 103, a mixer 121, a steam turbine 120, and a generator 122. The ammonia solution output from the mixer 121 flows sequentially through the condenser 119. 19. After passing through the first booster pump 106, the first heat exchanger 111, and the second heat exchanger 112, the solution enters the separator 103. The ammonia solution entering the separator 103 has a pressure of 4-55 bar, a temperature of 120-400℃, and a concentration of 20%-90%. Ammonia vapor is separated from the upper layer of the separator 103 and enters the turbine 120 to drive it to perform work, which in turn generates electricity via the generator 122. The generator 122 is electrically connected to the phase change energy storage device 600 and the end user. The solution returning from the bottom of the separator 103 and the exhaust gas from the turbine 120 outlet are mixed in the mixer 121 to form an ammonia solution.

[0036] The ammonia decomposition reactor 400 is used to decompose part of the ammonia fuel into hydrogen and nitrogen using the heat in the high-temperature flue gas. The reaction-side outlet of the ammonia decomposition reactor 400 is equipped with a three-stage temperature interlock protection device and a hydrogen concentration detector to prevent the catalyst from sintering and losing its activity, and to feed back the hydrogen volume concentration signal to the flue gas distribution control unit 500 to adjust the decomposition rate. The input end of the ammonia pipe 203 is connected to the main gasification heat exchanger 113, and the output end is connected to the ammonia decomposition reactor 400.

[0037] The flue gas distribution control unit 500 includes a high-temperature reforming branch 141, a medium-temperature driving branch 142, and a low-temperature gasification branch 143 connected in series. The high-temperature flue gas generated by the combustion reaction unit 200 flows sequentially through the three branches. The high-temperature reforming branch 141 is used to introduce the high-temperature flue gas into the ammonia decomposition reactor 400. The medium-temperature driving branch 142 is used to introduce the flue gas into the Karina circulation unit 300 to drive the ammonia water working fluid to generate steam for power generation. The low-temperature gasification branch 143 is used to introduce the flue gas into the main gasification heat exchanger 113 to provide heat for liquid ammonia gasification. The flue gas distribution control unit 500 also includes an exhaust pipe 204, a first flue gas temperature sensor 137, a second flue gas temperature sensor 138, a flue gas logic control unit 501, and a third valve 133, a fourth valve 134, and a fifth valve 135 electrically connected to the flue gas logic control unit 501. 35; The fourth valve 134 is installed on the exhaust pipe 204; the input end of the high-temperature reforming branch 141 is connected to the exhaust pipe 204, and the output end is connected to the ammonia decomposition reactor 400; the third valve 133 and the first flue gas temperature sensor 137 are sequentially installed on the high-temperature reforming branch 141; the input end of the medium-temperature driving branch 142 is connected to the ammonia decomposition reactor 400, and the output end is connected to the second heat exchanger 112; the input end of the low-temperature gasification branch 143 is connected to the second heat exchanger 112, and the output end is connected to the main gasification heat exchanger 113; the second flue gas temperature sensor 138 is installed on the low-temperature gasification branch 143; it also includes a first branch pipe 146, on which a fifth valve 135 is installed, the input end of which is connected to the main gasification heat exchanger 113, and the output end of which is connected to the exhaust pipe 204. The flue gas logic control unit 501 adjusts the flow distribution ratio between the exhaust pipe 204 and the high-temperature reforming branch 141 by adjusting the opening of the third valve 133, the fourth valve 134, and the fifth valve 135 according to the combustion load and hydrogen blending ratio requirements of the combustion reaction unit 200, so as to adjust the hydrogen production (i.e., decomposition rate) of the ammonia decomposition reactor 400 and achieve a hydrogen blending volume ratio in the ammonia-hydrogen mixed fuel of 5%-20%.

[0038] In the cryogenic recovery branch 201, liquid ammonia flows out from the liquid ammonia storage tank 101, and is cooled by the Karina circulation unit 300. The liquid ammonia itself is heated and supplied to the combustion reaction unit 200 and the ammonia decomposition reactor 400 respectively, forming a closed ammonia working fluid circulation. The phase change energy storage device 600 is divided into two stages: a high-temperature stage and a medium-temperature stage, which are respectively connected to the ammonia decomposition reactor 400 and the main gasification heat exchanger 113 to supplement the heat gap under varying operating conditions. The temperature range of the high-temperature stage is 400-600°C, and the temperature range of the medium-temperature stage is 100-200°C.

[0039] The regulation of the hydrogen blending volume ratio in ammonia-hydrogen blended fuel is executed by the electronic control unit (ECU), specifically in three steps: T1: Target determination. The ECU, based on engine speed and load, queries a 3D MAP (Modular Mapping) and determines a hydrogen blending volume ratio target of 5%-20%, prioritizing combustion stability and minimizing unburned ammonia emissions. T2: Pulse width calculation. Based on the hydrogen rail pressure (PH2) and temperature (TH2), and corrected using the state equation, the hydrogen pulse width is calculated using the flow pulse spectrum. Simultaneously, based on the liquid ammonia rail pressure (PNH3), the liquid ammonia pulse width is calculated using the flow pulse spectrum. T3: Closed-loop correction. The ECU, based on exhaust oxygen concentration or cylinder pressure signals, back-calculates the actual hydrogen blending ratio and dynamically corrects the pulse width using a PID or MPC controller, ensuring that the steady-state deviation of the hydrogen blending volume ratio does not exceed ±5%, and the transient deviation does not exceed ±10%. This precise regulation strategy ensures optimal matching of the hydrogen blending volume ratio under different operating conditions, consistently maintaining good combustion performance and improving the system's adaptability and operational stability under varying operating conditions.

[0040] Example 2

[0041] This embodiment details the specific application, workflow, and outstanding results of a scientifically verified and highly optimized ammonia fuel cogeneration system in the power scenario of large ships.

[0042] 1. System Core Configuration Ammonia-fueled internal combustion engine: 10MW ammonia-fueled low-speed two-stroke marine internal combustion engine: Total fuel consumption: 1.0kg / s. Flue gas source: Flow rate 6.0kg / s, temperature 470℃.

[0043] 2. Optimized energy cascade utilization process The core innovation of this system lies in the refined design of "grade matching and tiered utilization" of flue gas thermal energy.

[0044] First stage (high temperature reforming): 470℃→420℃; Heat extraction power: 330kW.

[0045] Function: This part uses high-grade heat energy to partially decompose gaseous ammonia at a rate of 0.2 kg / s through a countercurrent heat exchange ammonia decomposition reactor 400.

[0046] Key parameters: Under the action of a highly efficient catalyst, a decomposition rate of 25% and a hydrogen production rate of 0.0088 kg / s are achieved.

[0047] The flue gas outlet temperature is precisely set to 420℃, matching the upper limit of the optimal operating temperature for the next stage of the Karina cycle, achieving seamless connection of energy quality and minimizing loss.

[0048] In this embodiment, the ammonia decomposition reactor 400 and the main gasification heat exchanger 113 do not employ traditional shell-and-tube heat exchangers, but rather compact plate-fin heat exchangers or printed circuit board heat exchangers (PCHEs). The specific surface area (heat exchange area per unit volume) of these advanced heat exchangers is 10-50 times that of conventional methods. Therefore, a PCHE with a heat exchange area of ​​100 m² may only have a volume of 0.5-1 cubic meters, which can be fully integrated into the piping or reactor shell of a ship's engine room, perfectly meeting space-constrained requirements.

[0049] Second stage (medium-temperature power generation): 420℃→180℃ Heat extraction power: 1584kW.

[0050] Function: Utilizing the medium-grade thermal energy in this section, the ammonia-water working fluid within the Karina cycle unit 300 undergoes a Karina cycle. This cycle leverages the variable-temperature evaporation characteristics of the ammonia-water mixture to achieve a better match with the flue gas temperature curve, thereby efficiently driving the steam turbine 120 to generate electricity.

[0051] Key parameters: Net power generation is 285.1kW at a design efficiency of 18%.

[0052] Third stage (low-temperature vaporization): 180℃ → 133.3℃ Heat extraction power: ~308kW.

[0053] Function: Utilizing this portion of low-grade waste heat, 0.2 kg / s of liquid ammonia is completely vaporized in the main gasification heat exchanger 113, and then preheated to 45°C before being sent to the decomposition reactor.

[0054] 3. Detailed description of key equipment parameters To achieve the above-mentioned efficient process, the key design parameters for the ammonia decomposition reactor 400 are as follows: Type and structure: It adopts a fixed-bed reactor with an internally integrated counter-current heat exchanger to maximize thermal energy utilization efficiency.

[0055] Catalyst: A highly active ruthenium-based catalyst, specifically Ru / CeO2-Al2O3, with a ruthenium loading of 2 wt%, was selected. Ruthenium serves as the active component, while the CeO2 promoter enhances the metal-support interaction by providing oxygen vacancies, significantly improving the dispersibility and low-temperature activity of ruthenium.

[0056] Operating conditions: The reaction is carried out under low pressure on the flue gas side of the system. The peak temperature of the catalyst bed is controlled slightly below 470℃, and the average reaction temperature is 440-460℃.

[0057] Performance parameters: Under these temperature and catalyst conditions, when the reaction space velocity is maintained in the range of 1200-1800 h⁻¹, a stable decomposition rate of 25% can be achieved, ensuring efficient and stable operation.

[0058] 4. Fuel path, recovery and in-cylinder mixture composition This system employs sophisticated fuel management and recycling pathways to ensure both efficiency and safety.

[0059] Fuel path: Main path: 0.8 kg / s of liquid ammonia is directly injected into the cylinder via the high-pressure direct injection system 211.

[0060] Branch line: 0.2 kg / s of liquid ammonia undergoes "gasification-decomposition", and its products are processed separately.

[0061] Decomposition product treatment and recycling: Ammonia gas at a rate of 0.2 kg / s enters the ammonia decomposition reactor 400, of which 25% (i.e., 0.05 kg / s) is decomposed, producing hydrogen gas at a rate of 0.0088 kg / s and corresponding nitrogen gas.

[0062] The remaining 75% of undecomposed ammonia gas (0.15 kg / s) is guided out of the ammonia decomposition reactor 400, and after separation, compression, and cooling, it is returned to the liquid ammonia storage tank 101 for recycling, thus avoiding fuel waste.

[0063] Calculation of the theoretical air-fuel mixture composition in an ammonia fuel internal combustion engine: The fuel entering the cylinder of an ammonia-fueled internal combustion engine consists of only two parts: liquid ammonia in the main circuit and hydrogen produced in the branch circuit.

[0064] Total ammonia molar flow rate n entering the cylinder of an ammonia-fueled internal combustion engine NH3 =0.8kg / s≈47.06mol / s (based on 0.17kg / mol).

[0065] The molar flow rate n of hydrogen entering the cylinder of an ammonia-fueled internal combustion engine H2 =0.0088kg / s=4.40mol / s (based on 0.002kg / mol).

[0066] Hydrogen / ammonia molar ratio = n H2 / n NH3 =4.40 / 47.06≈0.094.

[0067] Theoretical hydrogen doping volume ratio = n H2 / (n H2 +n NH3 =4.40 / (4.40+47.06)≈8.55%.

[0068] This approximately 8.5% hydrogen blending ratio, and / or in-cylinder direct injection stratified combustion strategy, can significantly improve the combustion stability of ammonia fuel and effectively control the emissions of unburned ammonia and nitrogen oxides.

[0069] 5. Optional intelligent energy storage module (to cope with changing operating conditions) Function: To solve the problem of insufficient flue gas heat under low load conditions and maintain the temperature of the ammonia decomposition reactor at 400°C.

[0070] Medium: Ternary nitrate with a phase change temperature of ~420℃.

[0071] Capacity: Total thermal storage 648MJ (approximately equivalent to 3600kg of material).

[0072] Mode: Under high load, it charges and stores heat using electricity (approximately 300kW); under low load / transient conditions, it releases heat to the reactor through a high-temperature heat pipe (average power 120kW), which can sustain it for 1.5 hours.

[0073] 6. Intelligent control and combustion optimization Key decision variables: hydrogen yield, ammonia working fluid concentration, and gasification cooling capacity.

[0074] Control strategy: An optimization algorithm based on model predictive control (MPC) is adopted. High load (>80%) prioritizes hydrogen production, low load (<50%) maintains the minimum hydrogen blending ratio, and medium load involves comprehensive optimization. The control cycle is 10ms.

[0075] Combustion control: Hydrogen is injected early (30-50% phase of compression stroke), and liquid ammonia is injected late (90-95% phase). Based on closed-loop correction of exhaust oxygen / cylinder pressure signals, the steady-state hydrogen blending ratio deviation is ≤±5%.

[0076] Hydrogen-ammonia molar ratio: Target is 0.094 (corresponding to a theoretical hydrogen doping volume ratio of approximately 8.55%), significantly improving combustion.

[0077] 7. Overall System Performance and Benefits Total output power: 10MW (main shaft power) + 285.1kW (net power generation) = 10.285MW.

[0078] Waste heat utilization: After three-stage utilization, the flue gas temperature drops from 470℃ to 134.5℃, and can then be finally discharged into the atmosphere through a seawater cooler.

[0079] Environmental indicators: Unburned ammonia emissions <110ppm; combustion cycle variation rate reduced by 67%.

[0080] Dynamic response: Load change recovery time <7 seconds; after integrated energy storage, the lower limit of the effective working load range of the decomposition reactor can be extended to ~20%.

[0081] Control parameters: Karina circulating condensing pressure fluctuation ≤ ±3% Energy efficiency: Through the cascade utilization of chemical-physical energy coupling and cryogenic cold energy recovery, the overall energy efficiency of the system is significantly improved compared with traditional solutions.

[0082] Environmental indicators: A hydrogen blending ratio of 8.55% ensures that unburned ammonia and nitrogen are mixed. X O emissions have been significantly reduced, meeting stringent international maritime environmental regulations such as IMO Tier III.

[0083] Safety: Instantaneous mixing inside the cylinder eliminates the risk of explosion from externally premixed hydrogen; the closed ammonia working fluid circulation significantly reduces the risk of ammonia leakage.

[0084] Economic benefits: The additional 285.1kW of power generated can be used in the ship's electrical grid, reducing the operating time of auxiliary generator sets.

[0085] 8. Conclusion This embodiment demonstrates a scientifically verified and highly optimized integrated ammonia fuel energy system. Through precise energy cascade utilization design and a refined fuel recovery path, it achieves a key leap from theoretical feasibility to engineering practice, providing ocean-going vessels with an efficient, clean, safe, and economical zero-carbon power solution.

[0086] In this embodiment, the specific heat capacity of the flue gas used in the calculation is taken as 1.1 kJ / (kg•K), and the physical properties of ammonia (latent heat of vaporization, specific heat capacity) are referenced from the standard thermodynamic data table.

[0087] Example 3

[0088] Combination Figure 3 As shown, this embodiment is for the verification of preferred injection operating parameters. Method for determining parameter combinations: The optimal hydrogen rail pressure is based on the following engineering considerations: Injection and Mixing: To ensure effective turbulent mixing of hydrogen within the cylinder, the hydrogen rail pressure needs to be maintained within the range of 5-20 bar. Computational fluid dynamics (CFD) simulations and bench tests have verified that this pressure range can achieve injection velocities of 50-100 m / s, ensuring the formation of a uniform hydrogen-air mixture within the limited time of the compression stroke. Low-Pressure Limitation: When the pressure is below 5 bar, the injection momentum is severely insufficient, leading to a deterioration in the mixing process and a significant decrease in combustion efficiency. High-Pressure Limitation: When the pressure exceeds 40 bar, excessive demands are placed on the hydrogen permeation and hydrogen embrittlement resistance of the system piping, seals, and injector materials, drastically increasing system cost and long-term operational risks. Considering mixing effect, combustion stability, and system reliability, setting the hydrogen rail pressure between 5-20 bar is the preferred solution for this system.

[0089] Injection phase: When hydrogen is injected at a compression ratio of 30-50%, the in-cylinder temperature is 400-500℃, which avoids pre-ignition and ensures uniform mixing; when liquid ammonia is injected at 90-95%, the in-cylinder temperature is >650℃, which meets the conditions for rapid ammonia vaporization and ignition. When the phase deviation is >5%, the cycle variation rate (COV) deteriorates from 2.1% to 8.5%.

[0090] Pulse width accuracy: ±0.1ms accuracy corresponds to a hydrogen mass flow rate deviation of ±2.5%, implemented in the ECU through the Bosch CCP calibration protocol, and the hardware uses the Infineon TC3xx HSM module to capture the rising edge of the injector current.

[0091] To more clearly illustrate how the above-mentioned preferred parameters play a role in the actual combustion process and achieve excellent combustion performance, this embodiment further combines its core in-cylinder stratified combustion strategy and provides a detailed explanation of the working mechanism as follows: Detailed explanation of the three steps of in-cylinder compression ignition.

[0092] The core of the system described in this invention lies in achieving efficient and stable combustion of ammonia fuel. To this end, the system employs an advanced in-cylinder stratified combustion strategy, which, through precise control of the electronic control unit 213 (ECU), decomposes the fuel injection and ignition process within a single compression stroke into the following three key steps: Step 1: Hydrogen premixing injection (forming a pilot flame) Execution timing: 30%-50% of the engine compression stroke.

[0093] Technical objective: The goal of this stage is not to do work directly, but to form a homogeneous hydrogen-air mixture in the cylinder that is easy to ignite, serving as a "guide flame" or "ignition source" for the subsequent combustion of the main fuel.

[0094] Working mechanism: At this time, the piston is moving upwards, and the cylinder temperature (approximately 400-500℃) and pressure are moderate. The ECU controls the hydrogen direct injector 208 to inject hydrogen, and the hydrogen mixes thoroughly with air under the action of turbulence in the cylinder. This temperature range ensures a good mixing effect while effectively preventing uncontrolled pre-ignition of hydrogen due to excessively high temperature.

[0095] Step 2: Liquid ammonia main combustion injection (to release energy) Execution timing: at 90%-95% of the engine's compression stroke, i.e., when the piston is about to reach top dead center (TDC).

[0096] Technical objective: To introduce the main fuel—liquid ammonia—at the moment when the in-cylinder thermodynamic environment is most severe, in order to prepare for energy release.

[0097] Working mechanism: At this time, the temperature inside the cylinder has exceeded 650℃ and the pressure is extremely high. The ECU controls the liquid ammonia direct injector (207) to inject high-pressure liquid ammonia. After the liquid ammonia comes into contact with the high temperature and high pressure gas, it will instantly absorb heat, vaporize and rapidly diffuse to form a combustible mixture mainly composed of ammonia.

[0098] Step 3: Spark plug 150 co-ignition (triggering stratified combustion) Execution timing: The optimal ignition advance angle after the liquid ammonia injection begins and before the piston reaches top dead center.

[0099] Technical objective: To trigger and control the initiation of the entire combustion process.

[0100] Working Mechanism: Spark plug 150 does not ignite liquid ammonia, but rather the hydrogen-air mixture core prepared in step one, which has excellent combustion characteristics. After the hydrogen core burns, it generates extremely high temperatures, pressures, and a large number of reactive free radicals (such as H₂, O₂, OH₂), forming a powerful flame front. This flame front rapidly and steadily propagates outward, igniting the surrounding ammonia-air mixture, which is relatively difficult to ignite, formed from the vaporization of liquid ammonia.

[0101] Final Result: Through the aforementioned three steps of "premixing-main combustion-ignition," this system achieves a smooth and controllable combustion transition from the pilot flame (hydrogen) to the main fuel (ammonia). This not only successfully solves the fundamental problems of difficult ammonia fuel ignition and slow combustion speed, but also significantly improves combustion efficiency and stability through a stratified combustion strategy, significantly reducing the emissions of unburned ammonia and nitrogen oxides, and achieving clean and efficient power output.

[0102] Example 4

[0103] This embodiment describes the intelligent control strategy of the flue gas distribution control unit 500: This embodiment illustrates how the flue gas distribution control unit 500 dynamically adjusts under different load conditions of a 10MW power unit to optimize the overall performance of the system.

[0104] Control logic core: The flue gas logic control unit 501 of this system receives real-time load signals from the combustion reaction unit 200 ECU and, based on a preset control strategy, precisely controls the flue gas flow into the bypass branches, namely the high-temperature reforming branch 141, the medium-temperature driving branch 142, and the low-temperature gasification branch 143, by adjusting the opening of the fourth valve 134, the third valve 133, and the fifth valve 135, thereby dynamically adjusting the hydrogen production (i.e., ammonia decomposition rate) of the ammonia decomposition reactor 400.

[0105] Adjustment process under specific operating conditions: High load conditions (>80% load): Input: When the ECU detects that the host load exceeds 80%, it sends a "priority hydrogen production" command to the flue gas logic control unit 501.

[0106] Action: The flue gas logic control unit 501 reduces the opening of the fourth valve 134 and / or increases the opening of the third valve 133 and the fifth valve 135, so that more high-temperature flue gas is directly discharged from the exhaust pipe 204 and diverted to the bypass branch pipe.

[0107] Result: The flue gas flow rate and temperature entering the high-temperature reforming branch 141 both increased, which can improve the hydrogen production of the ammonia decomposition reactor 400 to meet the demand for a high hydrogen blending ratio (such as close to 20%) under high load, and ensure strong and stable combustion.

[0108] Low load conditions (<50% load): Input: When the host load is below 50%, the ECU issues a "maintain minimum hydrogen blending ratio" command.

[0109] Action: The flue gas logic control unit 501 increases the opening of the fourth valve 134 and decreases the opening of the third valve 133 and the fifth valve 135, allowing most of the flue gas to be discharged directly through the exhaust pipe 204, and only allowing a small amount of flue gas to enter the bypass branch pipe.

[0110] Results: The ammonia decomposition reactor 400 operated at low power, producing only the amount of hydrogen needed to maintain minimum stable combustion (approximately 5%), saving fuel and avoiding energy waste caused by excessive hydrogen production at low loads.

[0111] Medium load conditions (50%-80% load): Input: In this range, the ECU issues a "comprehensive optimization" command.

[0112] Action: The control unit dynamically and finely adjusts the opening of the fourth valve 134, the third valve 133, and the fifth valve 135 based on real-time combustion stability (such as the COV value monitored by the cylinder pressure sensor) and emission data.

[0113] Result: Under the premise of ensuring stable combustion, the system automatically finds the optimal balance point of the total system efficiency (main shaft power + Karina cycle power generation + hydrogen production benefits), thus achieving refined energy utilization.

[0114] Through the above control strategies, this system can intelligently respond to complex changes in the operating conditions of the ship's power system, achieving coordinated control of energy efficiency, emissions, and safety.

[0115] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the preferred embodiments above, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention should not depart from the spirit and scope of the present invention. Those skilled in the art can also make other changes within the spirit of the present invention and use them in the design of the present invention, as long as they do not deviate from the technical effects of the present invention. These changes made according to the spirit of the present invention should all be included within the scope of protection claimed by the present invention.

Claims

1. A combined ammonia fuel supply system integrating hydrogen production and the Karina cycle, characterized in that, include: The ammonia fuel supply unit (100) includes a liquid ammonia storage tank (101) and a main gasification heat exchanger (113) for providing a high-pressure liquid ammonia source and low-pressure gasified ammonia gas; Combustion reaction unit (200) is used to burn ammonia-hydrogen mixed fuel and generate high-temperature flue gas with a temperature ≥400°C; The Karina cycle unit (300) is used to drive the steam turbine (120) to generate electricity using the medium-temperature heat in the high-temperature flue gas, wherein the temperature range of the medium-temperature heat is 120-420°C. An ammonia decomposition reactor (400) is used to decompose part of the ammonia fuel into hydrogen and nitrogen using the heat in the high-temperature flue gas, and the decomposition rate is adjustable. The flue gas distribution control unit (500) controls the flue gas flow direction of the combustion reaction unit (200) and reduces the unburned ammonia emissions in its flue gas to a safe concentration.

2. The ammonia fuel cogeneration system according to claim 1, characterized in that, The flue gas distribution control unit (500) includes a high-temperature reforming branch (141), a medium-temperature driving branch (142), and a low-temperature gasification branch (143) connected in series. The high-temperature flue gas flows through the three branches in sequence to achieve cascaded energy utilization. The high-temperature reforming branch (141) is used to introduce the high-temperature flue gas into the ammonia decomposition reactor (400). The medium-temperature driving branch (142) is used to introduce the flue gas into the Karina circulation unit (300) to drive the ammonia water working fluid to generate steam for power generation. The low-temperature gasification branch (143) is used to introduce the flue gas into the main gasification heat exchanger (113) to provide heat for liquid ammonia gasification.

3. The ammonia fuel cogeneration system according to claim 1, characterized in that, The system includes a cryogenic recovery branch (201), from which liquid ammonia flows out of the liquid ammonia storage tank (101), and is cooled by the Karina circulation unit (300) to cool the working fluid of the Karina circulation unit (300). The liquid ammonia itself is heated and divided into two paths. The first path enters the combustion reaction unit (200) through the first pipeline (144), and 50-90% of the flow is injected into the cylinder in liquid form. The second path enters the main gasification heat exchanger (113) through the second pipeline (145), and 10-50% of the flow is injected into the ammonia decomposition reactor (400).

4. The ammonia fuel cogeneration system according to claim 2, characterized in that, The flue gas distribution control unit (500) further includes a flue pipe (204), a first flue gas temperature sensor (137), a second flue gas temperature sensor (138), a flue gas logic control unit (501), and a third valve (133), a fourth valve (134), and a fifth valve (135) electrically connected to the flue gas logic control unit (501); the fourth valve (134) is located on the flue pipe (204); The input end of the high-temperature reforming branch (141) is connected to the flue pipe (204), and the output end is connected to the ammonia decomposition reactor (400). The third valve (133) and the first flue gas temperature sensor (137) are sequentially installed on the high-temperature reforming branch (141). The input end of the medium-temperature drive branch (142) is connected to the ammonia decomposition reactor (400), and the output end is connected to the second heat exchanger (112). The input end of the low-temperature gasification branch (143) is connected to the second heat exchanger (112), and the output end is connected to the main gasification heat exchanger (113); the second flue gas temperature sensor (138) is installed on the low-temperature gasification branch (143); It also includes a first branch pipe (146), on which a fifth valve (135) is provided, the input end of which is connected to the main gasification heat exchanger (113), and the output end is connected to the flue pipe (204). The flue gas logic control unit (501) adjusts the flow distribution ratio between the exhaust pipe (204) and the high-temperature reforming branch (141) by adjusting the opening of the third valve (133), the fourth valve (134), and the fifth valve (135) according to the combustion load and hydrogen blending ratio requirements of the combustion reaction unit (200), so as to adjust the hydrogen production of the ammonia decomposition reactor (400) and achieve a hydrogen blending volume ratio range of 5%-20% in the ammonia-hydrogen mixed fuel.

5. The ammonia fuel cogeneration system according to claim 1, characterized in that, The combustion reaction unit (200) includes an ammonia fuel internal combustion engine and a fuel injection system (210); the fuel injection system (210) includes: Liquid ammonia direct injection system (211): includes a high-pressure ammonia pump (209) and a liquid ammonia direct injector (207). The high-pressure ammonia pump (209) is located on the first pipeline (144). The cryogenic recovery branch (201) is branched to the first pipeline (144) after passing through the condenser (119). The output end of the first pipeline (144) is connected to the liquid ammonia direct injector (207). Hydrogen direct injection system (212): includes a hydrogen supply device (104) and a hydrogen direct injector (208), which are connected by a hydrogen pipe (206); The liquid ammonia direct injector (207) and the hydrogen direct injector (208) are respectively connected to the cylinder of the ammonia fuel internal combustion engine; Electronic control unit (213): configured to control the opening of the hydrogen direct injector (208) and the liquid ammonia direct injector (207) at different phases of the engine compression stroke, and dynamically adjust the hydrogen / ammonia injection ratio according to the internal combustion engine operating conditions to achieve stratified combustion in the internal combustion engine cylinder.

6. The system according to claim 5, characterized in that, The fuel injection system supports closed-loop feedback correction, and its operating parameters are as follows: Pressure setting: The high-pressure ammonia pump pressurizes liquid ammonia to ≥50 bar, and the hydrogen supply device maintains the hydrogen rail pressure at 5-20 bar; Phase setting: The electronic control unit (213) controls the hydrogen direct injector to start injection within the 30%-50% phase of the compression stroke, and controls the liquid ammonia direct injector to start injection within the 90%-95% phase of the compression stroke, and ensures that the hydrogen injection ends before the ammonia injection begins. Accuracy setting: The control accuracy of the electronic control unit (213) for the hydrogen doping volume ratio is: steady state deviation ≤ ±5%, transient deviation ≤ ±10%.

7. The system according to claim 4, characterized in that, The electrical energy generated by the Karina cycle unit is stored in a phase change energy storage device (600), which is divided into a high-temperature section and a medium-temperature section. The temperature range of the high-temperature section is 400-600℃, and the temperature range of the medium-temperature section is 100-200℃. These sections are connected to the ammonia decomposition reactor (400) and the main gasification heat exchanger (113), respectively. When the inlet temperature of the high-temperature reforming branch (141) is detected by the first flue gas temperature sensor (137) as T1≤400℃, the phase change energy storage device (600) releases the latent heat of the high-temperature section to supplement the heating of the ammonia decomposition reactor (400). When the inlet temperature of the low-temperature gasification branch (143) is detected by the second flue gas temperature sensor (138) as T2≤180℃, the phase change energy storage device (600) releases the latent heat of the medium-temperature section to supplement the heating of the main gasification heat exchanger (113), forming a closed loop for the utilization of electrical energy. The gasification cooling capacity is obtained by real-time calculation of the temperature difference between the inlet and outlet of the main gasification heat exchanger and the liquid ammonia flow rate.

8. The ammonia fuel cogeneration system according to claim 1, characterized in that, The Karina circulation unit (300) includes a condenser (119), a first booster pump (106), a first heat exchanger (111), a second heat exchanger (112), a separator (103), a mixer (121), a steam turbine (120), and a generator (122). The ammonia solution output from the mixer (121) flows sequentially through the condenser (119), the first booster pump (106), the first heat exchanger (111), and the second heat exchanger (112) before entering the separator (103). The separator (103) separates ammonia vapor from the upper layer, which enters the steam turbine (120) to drive it to do work and generate electricity through the generator (122). The generator (122) is electrically connected to the phase change energy storage device (600) and the end user. The solution returning from the bottom of the separator (103) and the exhaust gas from the outlet of the steam turbine (120) are mixed in the mixer (121) to form an ammonia solution.

9. A method for operating an ammonia fuel cogeneration system using the coupled hydrogen production and Karina cycle as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Liquid ammonia flows out from the liquid ammonia storage tank (101), and is cooled by the condenser (119) of the Karina circulation unit (300) to cool the Karina circulation working fluid, while the liquid ammonia itself is heated; S2: The heated liquid ammonia is divided into two transmission routes: 50% to 90% of the flow enters the main route and is injected into the ammonia fuel internal combustion engine in liquid form through the fuel injection system (210); 10% to 50% of the flow enters the branch route, is vaporized through the main gasification heat exchanger (113) and then enters the ammonia decomposition reactor (400). S3: The high-temperature flue gas in the ammonia fuel internal combustion engine in step S2, part of which flows through the high-temperature reforming branch (141) to drive the decomposition of ammonia to produce hydrogen and nitrogen; S4: The hydrogen produced in step S3 and the liquid ammonia produced in step S2 are injected into the cylinder of the ammonia fuel internal combustion engine through an independent fuel injection system (210) to achieve in-cylinder mixing and combustion during the compression stroke, forming high-temperature flue gas; S5: In steps S3 and S4, the high-temperature flue gas generated in the ammonia fuel internal combustion engine flows sequentially through the high-temperature reforming branch (141) to drive ammonia decomposition to produce hydrogen, the medium-temperature driving branch (142) to drive the Karina cycle power generation, and the low-temperature gasification branch (143) to supply energy for liquid ammonia gasification.

10. The operation method of the ammonia fuel cogeneration system coupled with hydrogen production and the Karina cycle according to claim 9, characterized in that, The in-cylinder mixing injection method in step S4 is as follows: Hydrogen-guided injection: Hydrogen is injected during the 30%-50% phase of the compression stroke to form a lean mixture; Ammonia fuel main injection: Liquid ammonia is injected at a pressure of ≥50 bar during the 90%-95% phase of the compression stroke and ignited by a hydrogen flame. The hydrogen volume ratio in the ammonia-hydrogen blended fuel is 5%-20%; Furthermore, the hydrogen-guided injection ends before the main ammonia fuel injection begins.

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