An ammonia and brown gas dual fuel engine and a control method thereof

Abstract

This invention relates to an ammonia and Brown gas dual-fuel engine and its control method. While adding hydrogen to improve the slow flame propagation, high ignition energy, and poor combustion stability of ammonia fuel, problems exist such as the dangers of hydrogen storage and transportation, the susceptibility to high-load knocking, and the complexity and inefficiency of the reforming hydrogen production system. The engine structure is designed and constructed using Brown gas supply components, a central controller, and a liquid ammonia storage tank. Brown gas, with its high calorific value, low ignition energy, and fast flame propagation speed, is used as a combustion improver to increase the combustion rate of the in-cylinder mixture and improve the combustion performance of ammonia fuel. Brown gas is produced and used immediately, avoiding storage and transportation risks. Brown gas is injected into the intake manifold along with the air intake, while liquid ammonia is directly injected into the cylinder. The central controller, based on engine speed, load, and sensor feedback, combined with a calibrated pulse spectrum, executes single or multiple injection strategies to vaporize the liquid ammonia, absorb heat, and reduce the local temperature inside the cylinder, actively suppressing knocking. The engine is simple in structure, highly efficient, achieves stable and efficient combustion of ammonia fuel, is low in cost, and has good safety.

Description

Technical Field

[0001] This invention relates to the field of dual-fuel engine technology, and more particularly to an ammonia and Brown gas dual-fuel engine and its control method. Background Technology

[0002] With the implementation of the strategic goal of "carbon peaking and carbon neutrality," hydrogen, as a clean and renewable energy source, has received attention and faced challenges. However, due to numerous bottlenecks in its manufacturing, storage, and transportation technologies, large-scale commercial application has not yet been realized. Compared to hydrogen, ammonia, as a hydrogen carrier, is carbon-free and easily liquefied. It can be stored in liquid form at room temperature with only about 9 bar pressure or by cooling to -33°C at atmospheric pressure. Furthermore, the volumetric energy density of liquid ammonia is approximately 1.6 times that of liquid hydrogen, giving it a significant advantage as an energy carrier. However, the direct application of ammonia as fuel in engines remains limited, mainly due to slow flame propagation speed, high ignition energy, and a narrow combustible range. Additionally, in spark-ignition engines, the stability of pure ammonia combustion under low-load conditions is poor; in compression-ignition engines, the compression ratio required for reliable ignition of pure ammonia is as high as 35 or more, making it difficult to apply in practice. Therefore, overcoming the inherent combustion inertia of ammonia fuel to achieve its efficient and stable application has become a core technical challenge in its application to engines.

[0003] Currently, the main technologies for achieving stable combustion of ammonia fuel in engines are as follows:

[0004] One approach involves physically blending ammonia with highly reactive fuels. This method involves directly introducing easily combustible auxiliary fuels such as gasoline, natural gas, or hydrogen into the engine's fuel supply end, mixing them with ammonia, and then sending the mixture into the cylinder for combustion. For example, CN116291919B discloses a control method and system for the periodic and specific proportion blending and combustion of natural gas. This method uses intake manifold injection to mix natural gas and ammonia before supplying them to the engine. Through control logic, such as coolant temperature judgment, pulse spectrum determination, and air-fuel ratio closed-loop compensation, the stable combustion of the mixed fuel is ensured, reducing carbon emissions. However, this approach still relies on fossil fuels and cannot achieve zero emissions, let alone direct injection into the engine.

[0005] Secondly, ammonia is partially cracked into more reactive hydrogen and nitrogen using an online reforming unit, which is then used for blending; this is known as ammonia reforming to produce hydrogen blending technology. This technology utilizes external energy sources such as engine exhaust heat or plasma to crack a portion of ammonia into a mixture of more reactive hydrogen and nitrogen, which is then fed into the cylinder for combustion along with ammonia. For example, CN120968967A discloses an ammonia fuel reforming system and method suitable for ammonia-fueled engines, including devices for liquid ammonia supply, preheating, decomposition, pressurization, and injection. It utilizes the synergistic effect of engine exhaust heat and plasma to crack ammonia online into an ammonia-hydrogen mixture containing 5-15% hydrogen, thereby improving the combustion performance of ammonia. Another example is CN117231389A, which discloses an ammonia-fueled internal combustion engine hybrid system and its control method. It designs a multi-stage heat exchange system, using the high-temperature mixture generated from cracking to preheat liquid ammonia or ammonia gas, achieving energy cascade utilization. For example, CN117128087B discloses an ammonia-hydrogen engine and its control method, which directly uses pure hydrogen as a combustion aid. Through timing control, it improves the combustion of ammonia with hydrogen while effectively suppressing the risk of knocking under high load conditions. However, this method requires the pre-storage of pure hydrogen, resulting in high hydrogen storage and transportation costs and significant safety risks, which severely limits its widespread use.

[0006] In summary, existing technologies for achieving stable combustion of ammonia fuel in engines still face numerous technical challenges. Firstly, ammonia cannot be directly injected into the engine; it must be mixed with active fuel components before injection. Secondly, the reforming process for hydrogen production involves a complex and costly system where some of the cracked ammonia is converted into hydrogen and then mixed with the ammonia gas. Furthermore, the energy conversion efficiency is low, and the reforming catalyst exhibits insufficient activity at low temperatures, resulting in low production efficiency. Thirdly, hydrogen production, storage, and transportation are difficult, costly, and dangerous. There is a lack of precise and coordinated injection control methods for ammonia fuel and oxidizers under high-load conditions, making it difficult to simultaneously achieve high power output and knock-free stable operation, and making knocking highly likely under high-load conditions. Finally, the fuel supply method is singular, lacking flexible and composite injection strategies designed based on the differences in the physicochemical properties of ammonia and oxidizers, making it difficult to meet optimized combustion requirements under different loads. Summary of the Invention

[0007] Based on the above-mentioned technical problems, the present invention provides a dual-fuel engine of ammonia and Brown gas and its control method, which uses Brown gas "produced and used immediately" as a combustion aid for ammonia fuel to achieve direct injection into the engine for mixed combustion.

[0008] The specific technical solution is as follows:

[0009] One objective of this invention is to provide a dual-fuel engine for ammonia and Brown gas, comprising an engine body, a Brown gas supply assembly, a central controller, and a liquid ammonia storage tank. The engine body is a spark-ignition reciprocating piston internal combustion engine. The engine body contains a combustion chamber, with a coolant flow channel between the combustion chamber and the inner wall of the engine body. The combustion chamber is equipped with a spark plug for igniting the gas mixture, an exhaust pipe for discharging exhaust gases generated during combustion, an intake pipe for connecting to and supplying the combustion chamber with a mixture of air and Brown gas, and a liquid ammonia injector. A liquid ammonia supply monitoring assembly is located between the liquid ammonia injector and the liquid ammonia storage tank. A cooling system is installed within the coolant flow channel. The engine body includes a liquid ammonia injector, a knock sensor on its outer wall, an exhaust oxygen sensor in its exhaust pipe, and an intake pressure sensor in its intake pipe. A Brown gas injector is installed on the intake pipe and connected to a Brown gas supply assembly, with a one-way valve between the injector and the supply assembly. A crankshaft position sensor is located on the front end of the crankshaft. The spark plug, liquid ammonia injector, Brown gas injector, liquid ammonia supply monitoring assembly, coolant sensor, knock sensor, exhaust oxygen sensor, intake pressure sensor, one-way valve, crankshaft position sensor, and Brown gas supply assembly are all electrically connected to the central controller.

[0010] This invention addresses the problems of slow flame propagation, high ignition energy, and poor combustion stability associated with ammonia fuel, which can be improved by adding hydrogen. However, hydrogen storage and transportation are dangerous and prone to causing high-load knocking, while reforming hydrogen production systems are complex and inefficient. Through engine structural improvements, including the design of the Brown gas supply component, central controller, and liquid ammonia storage tank, Brown gas (a hydrogen-oxygen mixture) produced by water electrolysis is used as a combustion aid. Brown gas has a high calorific value, low ignition energy, and fast flame propagation speed, significantly improving the combustion rate of the in-cylinder mixture and enhancing the ignition and combustion performance of ammonia fuel. Furthermore, Brown gas is produced and used immediately, avoiding storage and transportation risks. Brown gas is injected into the intake manifold along with the air intake, while liquid ammonia is directly injected into the cylinder. The central controller, based on operating conditions such as engine speed and load, as well as sensor feedback and a calibrated pulse spectrum, executes single or multiple injection strategies. The heat absorption from liquid ammonia vaporization reduces the local temperature within the cylinder, actively suppressing knocking. The design is simple, efficient, achieves stable and efficient combustion of ammonia fuel, is low-cost, and safe.

[0011] In order to achieve accurate control of engine operating performance, preferably, the liquid ammonia monitoring and supply component includes a common rail connecting the liquid ammonia injector and the liquid ammonia storage tank, an ammonia pressure sensor is installed in the common rail, and a liquid ammonia pump is installed between the ammonia pressure sensor and the liquid ammonia storage tank; both the ammonia pressure sensor and the liquid ammonia pump are electrically connected to the central controller.

[0012] To enable Brown gas to be used "on demand" as a combustion aid for ammonia fuel, preferably, the Brown gas supply assembly includes a Brown gas supply body and an adjustable DC power supply, a generator, and a backfire prevention assembly disposed within the Brown gas supply body; the generator includes electrodes for a cathode and an anode, with oxygen generated at the anode and hydrogen generated at the cathode during electrolysis; the adjustable DC power supply is electrically connected to the electrodes of the generator; the generator is provided with a mixing pipe for collecting oxygen and hydrogen, and the mixing pipe is connected to the Brown gas injector via the backfire prevention assembly; the adjustable DC power supply is electrically connected to the central controller.

[0013] To improve the safety of unidirectional Brown gas delivery, preferably, a one-way valve is provided between the anti-backfire assembly and the Brown gas injector.

[0014] In some technical solutions of this invention, the anti-backfire assembly includes several layers of metal filter screens along the gas flow direction and / or a water seal partition component along the gas flow direction. This simplifies the overall improved structure of the anti-backfire assembly and helps reduce improvement costs.

[0015] In some technical solutions of this invention, the water seal isolation component includes an isolation body, a first connecting pipe extending into the bottom of the isolation body, and a second connecting pipe inserted into the top of the isolation body. The first connecting pipe communicates with the mixing pipe, and the second connecting pipe communicates with a Brown gas injector. The isolation body is filled with sealing water, which submerges the bottom end of the first connecting pipe, and the bottom end of the second connecting pipe is located above the horizontal plane of the sealing water. Preferably, a one-way valve is provided on the second connecting pipe.

[0016] Preferably, the central controller includes an input terminal and an output terminal. The input terminal is electrically connected to the crankshaft position sensor, intake pressure sensor, exhaust oxygen sensor, knock sensor, ammonia pressure sensor, and coolant sensor, respectively. The output terminal is electrically connected to the adjustable DC power supply, Brown gas injector, liquid ammonia pump, liquid ammonia injector, and spark plug, respectively.

[0017] Preferably, the central controller stores a control pulse spectrum diagram calibrated according to bench tests, and can obtain basic control parameters by looking up tables based on the current speed and load, and generate precise control commands after closed-loop correction by combining the input feedback parameters, and then output the control from the output end.

[0018] The second objective of this invention is to provide a control method for an ammonia and Brown gas dual-fuel engine, including the aforementioned ammonia and Brown gas dual-fuel engine. The central controller stores a control pulse spectrum diagram calibrated according to bench tests. It can look up basic control parameters based on the current speed and load, and generate precise control commands after closed-loop correction by combining the input feedback parameters, and then output the control from the output end.

[0019] Compared with the prior art, the technical effects of the invention are as follows:

[0020] The invention forms a dual injection structure system of ammonia and oxyhydrogen by using an oxyhydrogen supply assembly and a liquid ammonia supply monitoring assembly, so that oxyhydrogen and ammonia fuel can be directly injected into a combustion chamber respectively, and independent supply control of ammonia fuel and oxyhydrogen can be realized. Combined with the arrangement of structural components electrically connected to the input end of a central controller and the arrangement of structural components electrically connected to the output end of the central controller, the injection timing and injection times of ammonia fuel, oxyhydrogen and the like can be effectively controlled, so that a concentration stratification effect of a mixed gas formed by oxyhydrogen and ammonia fuel in the combustion chamber can be realized. Furthermore, the internal temperature is reduced by using the endothermic effect of ammonia gasification, thereby suppressing knocking and reducing the generation of nitrogen oxides.

[0021] In the invention, the oxyhydrogen supply assembly is constructed by adjustable direct current, a generator and a flashback prevention assembly for generating and conveying oxyhydrogen. Meanwhile, an oxyhydrogen injector is arranged in an air intake pipeline, so that a vacuum negative pressure process is formed in the combustion chamber, and oxyhydrogen is sucked in along with the suction of air, which effectively prevents premature ignition of high-activity oxyhydrogen in the injection and conveying process, is beneficial to forming uniform mixed gas, and reduces the probability and risk of knocking.

[0022] In the invention, in the liquid ammonia supply monitoring assembly, a common rail pipe is connected with a liquid ammonia injector, and an ammonia pressure sensor is arranged in the common rail pipe, which can monitor the pressure in the common rail pipe in real time and feed the pressure back to the central controller, so that the liquid ammonia injector is monitored and controlled by the central controller in real time, and the purpose of high-precision, multiple direct injection of ammonia fuel into a combustion cylinder is satisfied.

[0023] Through the above structural improvement, the invention fundamentally solves the technical problem of poor combustion performance of ammonia fuel, contributes to the rapid promotion of the zero carbon emission strategy, and realizes the composite supply of oxyhydrogen and ammonia fuel. Through the ignition and combustion acceleration effects of oxyhydrogen, the overall flame propagation speed and combustion stability of the mixed gas in the cylinder are significantly improved, the inherent defects of difficult ignition and slow combustion of ammonia fuel are effectively overcome, and stable and efficient operation of an engine is realized.

[0024] The invention realizes the "instant production and instant use" of oxyhydrogen. By combining the improvement of the engine structure, oxyhydrogen is prepared by electrolyzing aqueous solution in real time according to the requirements of the engine and directly supplied to the engine for use. High-cost and high-risk hydrogen storage and transportation links are avoided, the system has simpler structure, higher safety and lower use cost in the whole life cycle, and has good commercial promotion value. Description of Drawings

[0025] In order to enable those skilled in the art to fully understand the technical solution of the present invention, the following description is made in conjunction with the technical solution content and the accompanying drawings. This description is not intended to limit the technical solution of the present invention.

[0026] Figure 1 A schematic diagram of the structure of a dual-fuel engine using ammonia and Brown gas is provided for this invention.

[0027] Figure 2 A schematic diagram of the control method for this invention.

[0028] 1-Engine body 2-Brown gas supply assembly 3-Central controller 4-Spark plug 5-Liquid ammonia injector 6-Ammonia pressure sensor 7-Liquid ammonia pump 8-Liquid ammonia storage tank 9-Exhaust pipe 10-Exhaust oxygen sensor 11-Combustion chamber 12-Crankshaft position sensor 13-Coolant sensor 14-Knock sensor 15-Intake pressure sensor 16-Brown gas injector 17-One-way valve 18-Intake pipe;

[0029] 2.1-Adjustable DC power supply 2.2-Generator 2.3-Backfire prevention assembly. Detailed Implementation

[0030] To facilitate a correct understanding of the present invention by those skilled in the art, and to enable them to fully understand the technical content of the present invention, the technical solution of the present invention will be further described below in conjunction with specific embodiments. However, this description does not limit the scope of protection claimed by the present invention. Those skilled in the art should not limit the scope of protection of the present invention to the following description. Any equivalent substitutions or changes made by those skilled in the art or those familiar with the art based on the present invention, and based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0031] like Figure 1As shown, in some embodiments, an ammonia and Brown gas dual-fuel engine includes an engine body 1, a Brown gas supply assembly 2, a central controller 3, and a liquid ammonia storage tank 8; the engine body 1 is a spark-ignition reciprocating piston internal combustion engine; the engine body 1 has a combustion chamber 11, and a coolant flow channel is formed between the combustion chamber 11 and the inner wall of the engine body 1; the combustion chamber 11 is equipped with a spark plug 4, an exhaust pipe 9, an intake pipe 18, and a liquid ammonia injector 5; a liquid ammonia supply monitoring assembly is provided between the liquid ammonia injector 5 and the liquid ammonia storage tank 8; a coolant sensor 13 is provided in the coolant flow channel; a knock sensor 14 is provided on the outer wall of the engine body 1; and exhaust oxygen is provided in the exhaust pipe 9. Sensor 10; intake pressure sensor 15 is provided inside intake pipe 18; Brown gas injector 16 is provided on intake pipe 18, Brown gas injector 16 is connected to Brown gas supply assembly 2, and a one-way valve 17 is provided between Brown gas injector 16 and Brown gas supply assembly 2; crankshaft position sensor 12 is provided on the front end of crankshaft of engine body 1; spark plug 4, liquid ammonia injector 5, Brown gas injector 16, liquid ammonia supply monitoring assembly, coolant sensor 13, knock sensor 14, exhaust oxygen sensor 10, intake pressure sensor 15, one-way valve 17, crankshaft position sensor 12 and Brown gas supply assembly 2 are all electrically connected to central controller 3.

[0032] Through the design and improvement of the Brown gas supply component and the liquid ammonia supply monitoring component, it is possible to directly inject ammonia fuel into the engine combustion chamber, and to inject Brown gas into the intake pipe of the engine combustion chamber as needed. By utilizing the intake stroke along with the air, the phenomenon of combustion occurring before the gas enters the combustion chamber is avoided, thereby reducing the probability and risk of engine knock.

[0033] like Figure 1 As shown, in some embodiments, the liquid ammonia monitoring and supply assembly includes a common rail connecting the liquid ammonia injector 5 and the liquid ammonia storage tank 8. An ammonia pressure sensor 6 is installed within the common rail, and a liquid ammonia pump 7 is installed between the ammonia pressure sensor 6 and the liquid ammonia storage tank 8. Both the ammonia pressure sensor 6 and the liquid ammonia pump 7 are electrically connected to the central controller 3. The central controller receives feedback information to control the ammonia pump's injection of ammonia fuel, enabling precise and coordinated control of the ammonia fuel injection, which helps improve the combustion efficiency and effect of the ammonia and Brown gas mixture.

[0034] like Figure 1As shown, in some embodiments, the Brown gas supply assembly 2 includes a Brown gas supply body and an adjustable DC power supply 2.1, a generator 2.2, and a backfire prevention assembly 2.3 disposed within the Brown gas supply body. The generator 2.2 includes cathode and anode electrodes; during electrolysis, oxygen is generated at the anode and hydrogen at the cathode. The adjustable DC power supply 2.1 is electrically connected to the electrodes of the generator 2.2. The generator 2.2 is provided with a mixing pipe for collecting oxygen and hydrogen, and the mixing pipe is connected to the Brown gas injector 16 via the backfire prevention assembly 2.3. Both the adjustable DC power supply 2.1 and the generator 2.2 are electrically connected to the central controller 3. This avoids the risk of backfire and allows Brown gas to be produced on demand and directly supplied to the engine, avoiding the Brown gas storage and transportation process, which helps to improve the safety factor and promote the widespread application of Brown gas in ammonia fuel system engines.

[0035] In some embodiments of the present invention, a one-way valve 17 is provided between the anti-backfire assembly 2.3 and the Brown gas injector 16. The structure is simple, easy to improve, and inexpensive. Specifically, the anti-backfire assembly 2.3 has several layers of metal filter screens along the gas flow direction and / or a water seal isolation component is provided within the anti-backfire assembly 2.3 along the gas flow direction.

[0036] The water seal isolation component of this invention includes an isolation body, a first connecting pipe extending into the bottom of the isolation body, and a second connecting pipe inserted into the top of the isolation body. The first connecting pipe is connected to the mixing pipe, and the second connecting pipe is connected to the Brown gas injector 16. The isolation body is filled with sealing water, which submerges the bottom end of the first connecting pipe, and the bottom end of the second connecting pipe is located above the horizontal plane of the sealing water. A one-way valve 17 is provided on the second connecting pipe.

[0037] In this invention, the central controller 3 includes an input terminal and an output terminal. The input terminal is electrically connected to the crankshaft position sensor 12, intake pressure sensor 15, exhaust oxygen sensor 10, knock sensor 14, ammonia pressure sensor 6, and coolant sensor 13, respectively. The output terminal is electrically connected to the adjustable DC power supply 2.1, Brown gas injector 16, liquid ammonia pump 7, liquid ammonia injector 5, and spark plug 4, respectively. This effectively satisfies the requirement that the input terminal provides feedback to the central controller based on the operating conditions, and the central controller generates accurate commands to control the operation of the output terminal based on the feedback, which helps to improve the stability of the combustion operation of the ammonia and Brown gas dual-system fuel engine directly injected into the engine.

[0038] like Figure 2As shown, a control method for an ammonia and Brown gas dual-fuel engine includes the aforementioned ammonia and Brown gas dual-fuel engine. The central controller 3 stores a control pulse spectrum calibrated based on bench tests. It can retrieve basic control parameters from a lookup table based on the current engine speed and load, and after closed-loop correction using input feedback parameters, generate precise control commands and output them from the output end. By storing the control pulse spectrum calibrated based on bench tests in the central controller, the central controller, according to the current engine speed, load, and other operating conditions, follows the method described above. Figure 2 The control logic method shown retrieves basic control parameters by looking up a table, and after closed-loop correction based on the input feedback parameters, generates a precise control command, which is then output from the output. This ensures effective control of the injection of Brown gas and ammonia fuel.

[0039] like Figure 2 As shown, in some embodiments of the present invention, the control pulse spectrum calibrated according to bench tests includes, but is not limited to, the basic ammonia injection pulse spectrum, the Brown gas mixing ratio pulse spectrum, the liquid ammonia injection timing and injection frequency pulse spectrum, and the ignition advance angle pulse spectrum. This enables the central controller to obtain basic control parameters by looking up tables based on several operating conditions such as current speed and load. After combining these parameters or data that are electrically connected to the input terminal of the central controller and fed back to the central controller for closed-loop correction, the overall control logic generates precise control commands.

[0040] For start-up and warm-up control: When the coolant temperature sensor 13 detects a temperature below a preset threshold (e.g., 60℃), the central controller determines it to be a cold start or warm-up condition. At this time, generator 2.2 starts to produce Brown gas until stable gas production. Before stable gas production, the central controller first controls the liquid ammonia injector 5 to perform a direct injection into the combustion chamber (in-cylinder), and controls the spark plug 4 to perform multiple high-energy ignitions near the top dead center of the engine compression stroke, using a small amount of liquid ammonia combustion to raise the temperature of the combustion chamber (in-cylinder). When generator 2.2 is operating at full power to produce Brown gas, the Brown gas supply is stable. The central controller controls the Brown gas injector 16 to inject into the intake manifold 18, which reduces the negative pressure in the combustion chamber (in-cylinder) to draw in Brown gas and reduces the corresponding amount of ammonia fuel injection, allowing the engine to smoothly transition to normal operating conditions, thereby achieving the purpose of rapid and stable cold start.

[0041] For idling and low-load conditions, the central controller implements a single-injection strategy for Brown gas direct injection into the intake manifold and ammonia fuel direct injection into the combustion chamber (cylinder): During the intake stroke, the Brown gas injector 16 is opened, and the negative pressure in the combustion chamber draws in Brown gas, which mixes with air to form a lean mixture (Brown gas accounts for 10-20% of the total calorific value of the fuel); in the later stage of the intake stroke or the early stage of the compression stroke, the central controller controls the liquid ammonia injector 5 to perform a single in-cylinder direct injection into the combustion chamber (cylinder), and before the top dead center of the compression stroke, the ECU controls the spark plug (102) to ignite. Because the ignition energy of Brown gas is extremely low, it can be quickly ignited to form a high-temperature, high-speed flame, which then ignites the surrounding ammonia gas, thereby ensuring stable combustion.

[0042] For medium-to-high load conditions, the central controller implements a two-stage injection strategy: direct injection of Brown gas into the intake manifold and direct injection of ammonia fuel into the combustion chamber (in-cylinder). The first injection occurs during the intake stroke, where the central controller opens the Brown gas injector 16 to inject Brown gas into the intake manifold. The negative pressure in the combustion chamber draws in the Brown gas (10-15% of the Brown gas is drawn in). Simultaneously, the central controller controls the liquid ammonia injector 5 to perform the first in-cylinder direct injection (40-60% of the total required injection amount), resulting in a homogeneous mixture of Brown gas, air, and ammonia fuel, effectively ensuring ignition reliability. The second injection occurs in the later stages of the compression stroke, 30° to 60° before the crankshaft reaches top dead center. The central controller controls the liquid ammonia injector 5 to perform the second in-cylinder direct injection of the remaining ammonia fuel. This allows the ammonia fuel to rapidly atomize and vaporize under the high temperature and pressure generated by the first injection, absorbing a large amount of heat from the combustion chamber, effectively reducing the local temperature in the combustion chamber, and helping to suppress knocking. At the same time, it can stratify the fuel concentration in the combustion chamber and ignite it using the high-temperature flame generated by the first combustion. This controls the spark plug ignition timing to be 10°-20° before the compression top dead center.

[0043] Under heavy load conditions, the central controller controls and executes a three-stage injection strategy: Brownian gas direct injection into the intake manifold and ammonia fuel direct injection into the combustion chamber (in-cylinder).

[0044] First stage (intake stroke): The central controller controls the Brown gas injector 16 to open the intake manifold and utilizes the negative pressure in the combustion chamber to draw in all the required Brown gas (5%-10% calorific value, reduced to suppress knocking). Simultaneously, the central controller controls the liquid ammonia injector 5 to perform the first in-cylinder (combustion chamber) direct injection (accounting for 30%-50% of the total). At this time, the Brown gas, some ammonia, and air form a relatively uniform lean mixture.

[0045] The second stage (mid-compression stroke): The central controller controls the liquid ammonia injector 5 to perform a second in-cylinder direct injection (accounting for 20%-30% of the total). The injected liquid ammonia rapidly vaporizes and absorbs heat, significantly reducing the temperature of the in-cylinder mixture, extending the flame propagation path, and disrupting the conditions for the spontaneous combustion of highly reactive Brownian gas.

[0046] The third stage (late compression stroke to top dead center, crankshaft angle 30° before top dead center to 10° after top dead center): The central controller controls the liquid ammonia injector 5 to perform the third direct injection into the cylinder (accounting for 20%-40% of the total). The central controller adjusts the precise timing and injection quantity of this injection in real time based on the signal from the knock sensor 14. This part of the liquid ammonia is injected very late, and its main function is not to participate in premixed combustion, but to rapidly cool the combustion chamber walls and end mixture through intense phase change endothermic reaction, thereby fundamentally eliminating the possibility of spontaneous combustion of the end mixture. Spark plug 4 ignites 5°-15° before top dead center of compression. Because a temperature and concentration stratification conducive to suppressing knock has been formed in the cylinder, the combustion process is stable and controllable.

[0047] Under all operating conditions, the central controller uses signals from the exhaust oxygen sensor to adjust the liquid ammonia injection quantity in real time, ensuring that the excess air coefficient (λ) is always controlled within the range of 0.8-1.0 (when Brownian gas is mixed in, it contains its own oxygen, and the air-fuel ratio control needs to be adjusted accordingly). Simultaneously, the central controller uses signals from the knock sensor to adjust the timing of the third liquid ammonia injection and the ignition advance angle in real time, proactively intervening before knock occurs.

[0048] This invention creates a specific control logic flow as follows: Figure 2 As shown. The introduction of this control logic helps improve the stability of the Brownian gas and ammonia dual-fuel engine in this invention, achieving precise and coordinated control. It accurately manages the formation process, concentration stratification, and combustion chemical reaction path of the in-cylinder mixture, ensuring stable ignition and combustion under low loads, suppressing knocking and improving thermal efficiency under high loads, thus achieving comprehensive optimization of engine power, economy, and emissions across the entire operating range. The control method under this logic allows for precise acquisition of crankshaft angles and generation of control commands, especially under high load conditions, enabling coordinated control of single injection of Brownian gas (or highly reactive hydrogen components) and multiple injections of liquid ammonia (e.g., during the intake stroke, late compression stroke, and near top dead center). Utilizing the phase change endothermic effect and high octane number characteristics of liquid ammonia during compression and combustion, it effectively reduces the local temperature of the combustion chamber, suppresses abnormal auto-ignition of the mixture, and completely eliminates knocking, ensuring stable and efficient engine operation even under high load conditions, thus helping to broaden the efficient operating range of the ammonia fuel engine.

[0049] For any other matters not covered in this invention, conventional technical means can be used to implement them, referring to existing technology or common knowledge known to those skilled in the art. For example, the central control in this invention can be implemented using a self-programmable controller or other controllers that can achieve the corresponding functions in the above embodiments, which are common in existing technology. For another example, the crankshaft position sensor 12, intake pressure sensor 15, exhaust oxygen sensor 10, knock sensor 14, ammonia pressure sensor 6, and coolant sensor 13 mentioned in this invention are all common in existing technology and can be purchased directly from the market. The coolant sensor 13 is used to measure the coolant temperature; the crankshaft position sensor 12 is used to measure the position of the crankshaft; the intake pressure sensor 15 is used to measure the overall pressure change in the intake manifold; the exhaust oxygen sensor 10 is used to detect the oxygen concentration or content in the exhaust gas; the knock sensor 14 is used to detect whether knocking has occurred in the engine; and the ammonia pressure sensor 6 is used to detect the pressure in the common rail supply system for ammonia fuel entering the combustion chamber. For example, the specific structure of the engine is the same as that of the engine in the prior art. Any structure not specified in this invention is based on the engine structure in the prior art.

Claims

1. A dual-fuel engine for ammonia and Brown gas, characterized in that, The engine includes an engine body (1), a Brown gas supply assembly (2), a central controller (3), and a liquid ammonia storage tank (8). The engine body (1) is a spark-ignition reciprocating piston internal combustion engine. The engine body (1) is equipped with a combustion chamber (11), and a coolant flow channel is formed between the combustion chamber (11) and the inner wall of the engine body (1). The combustion chamber (11) is equipped with a spark plug (4), an exhaust pipe (9), an intake pipe (18), and a liquid ammonia injector (5). A liquid ammonia supply monitoring assembly is provided between the liquid ammonia injector (5) and the liquid ammonia storage tank (8). A coolant sensor (13) is provided in the coolant flow channel, a knock sensor (14) is provided on the outer wall of the engine body (1), an exhaust oxygen sensor (10) is provided in the exhaust pipe (9), and the intake pipe (18) is provided with a liquid ammonia supply monitoring assembly. 8) An intake pressure sensor (15) is provided inside; a Brown gas injector (16) is provided on the intake pipe (18), the Brown gas injector (16) is connected to the Brown gas supply assembly (2), and a one-way valve (17) is provided between the Brown gas injector (16) and the Brown gas supply assembly (2); a crankshaft position sensor (12) is provided on the front end of the crankshaft of the engine body (1); the spark plug (4), liquid ammonia injector (5), Brown gas injector (16), liquid ammonia supply monitoring assembly, coolant sensor (13), knock sensor (14), exhaust oxygen sensor (10), intake pressure sensor (15), one-way valve (17), crankshaft position sensor (12) and Brown gas supply assembly (2) are all electrically connected to the central controller (3).

2. The ammonia and Brown gas dual-fuel engine as described in claim 1, characterized in that, The liquid ammonia monitoring and supply component includes a common rail pipe connecting the liquid ammonia injector (5) and the liquid ammonia storage tank (8). An ammonia pressure sensor (6) is installed in the common rail pipe, and a liquid ammonia pump (7) is installed between the ammonia pressure sensor (6) and the liquid ammonia storage tank (8). The ammonia pressure sensor (6) and the liquid ammonia pump (7) are both electrically connected to the central controller (3).

3. The ammonia and Brown gas dual-fuel engine as described in claim 1, characterized in that, The Brown gas supply assembly (2) includes a Brown gas supply body and an adjustable DC power supply (2.1), a generator (2.2), and a backfire prevention assembly (2.3) disposed within the Brown gas supply body. The generator (2.2) includes electrodes for a cathode and an anode. During electrolysis, oxygen is generated at the anode and hydrogen is generated at the cathode. The adjustable DC power supply (2.1) is electrically connected to the electrodes of the generator (2.2). The generator (2.2) is provided with a mixing pipe for collecting oxygen and hydrogen. The mixing pipe is connected to the Brown gas injector (16) via the backfire prevention assembly (2.3). The adjustable DC power supply (2.1) is electrically connected to the central controller (3).

4. The ammonia and Brown gas dual-fuel engine as described in claim 3, characterized in that, A one-way valve (17) is provided between the anti-backfire assembly (2.3) and the Brown gas injector (16).

5. The ammonia and Brown gas dual-fuel engine as described in claim 3, characterized in that, The anti-backfire assembly (2.3) is provided with several layers of metal filter screens along the gas flow direction and / or the anti-backfire assembly (2.3) is provided with water seal partitions along the gas flow direction.

6. The ammonia and Brown gas dual-fuel engine as described in claim 4, characterized in that, The water seal partition component includes a partition body, a first connecting pipe extending into the bottom of the partition body, and a second connecting pipe inserted from the top of the partition body. The first connecting pipe is connected to the mixing pipe, and the second connecting pipe is connected to the Brown gas injector (16). The partition body is filled with sealing water, which submerges the bottom end of the first connecting pipe, and the bottom end of the second connecting pipe is located above the horizontal plane of the sealing water.

7. The ammonia and Brown gas dual-fuel engine as described in claim 6, characterized in that, The second connecting pipe is equipped with a one-way valve (17).

8. The ammonia and Brown gas dual-fuel engine as described in claim 1, 2, or 3, characterized in that, The central controller (3) includes an input terminal and an output terminal. The input terminal is electrically connected to the crankshaft position sensor (12), intake pressure sensor (15), exhaust oxygen sensor (10), knock sensor (14), ammonia pressure sensor (6), and coolant sensor (13), respectively. The output terminal is electrically connected to the adjustable DC power supply (2.1), Brown gas injector (16), liquid ammonia pump (7), liquid ammonia injector (5), and spark plug (4), respectively.

9. The ammonia and Brown gas dual-fuel engine as described in claim 8, characterized in that, The central controller (3) stores a control pulse spectrum diagram calibrated according to bench tests. It can look up the basic control parameters according to the current speed and load, and generate precise control commands after closed-loop correction by combining the input feedback parameters and output the control from the output end.

10. A control method for a dual-fuel engine using ammonia and Brown gas, characterized in that, Including the ammonia and Brown gas dual-fuel engine as described in any one of claims 1-9, the central controller (3) stores a control pulse spectrum diagram calibrated according to bench tests, and can obtain basic control parameters by looking up a table according to the current speed and load, and generate precise control commands after closed-loop correction by combining the input feedback parameters and outputting control from the output end.

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