Engine hydrogen-ammonia two-stage reforming system capable of dynamically switching four strokes / six strokes

Abstract

A four-stroke / six-stroke dynamic switching engine hydrogen-ammonia two-stage reforming system comprises a primary reforming unit, a combustion control unit and a secondary reforming gas storage unit. A secondary reforming unit is arranged at the top of the cylinder cover; the primary reforming unit has a built-in heating function, and a catalyst layer for catalyzing ammonia reforming is arranged on the surface of the primary reforming unit; the primary reforming unit is used for primarily reforming passing ammonia-air mixed gas to form ammonia-hydrogen-air mixed gas; the secondary reforming gas storage unit comprises a reforming cavity and a gas storage valve, a catalyst layer for catalyzing ammonia gas reforming is arranged on the inner surface of the reforming cavity, and the reforming cavity is used for reforming mixed gas from a fuel chamber, generating hydrogen-rich mixed gas and completing staged storage and release of energy; and the mixed gas of the combustion chamber is stored and reformed at the last stage of the first compression stroke, and the generated hydrogen-rich mixed gas is released back to the combustion chamber after the first exhaust is finished.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine technology, and more specifically to a two-stage hydrogen-ammonia reforming system for engines with dynamic switching between four-stroke and six-stroke operation. Background Technology

[0002] The demand for clean and efficient power systems is increasingly urgent in sectors such as transportation, shipbuilding, and heavy equipment. Ammonia and hydrogen, as highly promising zero-carbon fuels, are considered ideal alternatives to traditional fossil fuels due to their relatively mature storage and transportation infrastructure and the absence of carbon pollution in their combustion products. However, both have significant drawbacks when used alone: ​​ammonia fuel has inherent defects such as low calorific value, high minimum ignition energy, and slow flame propagation speed, leading to unstable engine combustion and low efficiency; hydrogen fuel faces challenges such as low energy density during storage, high safety requirements for long-distance transportation, and high costs. Therefore, overcoming the limitations of single fuels and achieving efficient and reliable energy conversion has become a core challenge for the green upgrading of engine technology.

[0003] To balance the safety of ammonia storage and transportation with the combustion characteristics of hydrogen, existing technologies have incorporated ammonia reforming into hydrogen production combined with thermodynamic cycles. However, mainstream fuel supply methods, such as single-stage ammonia reforming, are often limited by the temperature field distribution and reaction kinetics within the reactor, resulting in incomplete ammonia decomposition and insufficient hydrogen yield. This makes it difficult to continuously provide the engine with a sufficient and stable hydrogen-air mixture, leading to limited combustion improvement. Another approach, direct ammonia / hydrogen injection, can partially improve ignition and flame propagation performance, but it is prone to ammonia escape, resulting in increased unburned ammonia emissions and nitrogen oxide formation. Furthermore, its system energy conversion efficiency still needs improvement.

[0004] In terms of thermodynamic cycle, traditional engines face inherent bottlenecks in pursuing high power density, such as excessively high maximum combustion pressure, increased heat load, and serious waste of exhaust heat, which restrict further breakthroughs in overall thermal efficiency.

[0005] Furthermore, existing combustion control strategies are mostly based on fixed ignition timing and injection patterns, lacking the ability to actively adapt to different engine load conditions. Under low load, the cylinder temperature and pressure are low, making it difficult for the ammonia mixture to ignite, easily leading to misfires or combustion cycle fluctuations. Under high load, however, poor matching between the energy release rate and the cylinder pressure rise rate can cause abnormal combustion phenomena such as knocking. This rigid control mode makes it difficult for the engine to achieve efficient, stable, and clean combustion simultaneously across a wide operating range, limiting its adaptability and operational reliability.

[0006] Therefore, there is an urgent need for a hydrogen-ammonia two-stage reforming and combustion control technology based on a novel thermodynamic cycle to solve the technical problems of existing ammonia-hydrogen fuel engines, such as low fuel conversion efficiency, poor combustion stability, limited operating conditions, and insufficient emission control. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a two-stage hydrogen-ammonia reforming system for engines with dynamic switching between four-stroke and six-stroke operation. The reforming system achieves efficient fuel conversion and on-demand supply through staged hydrogen production in the intake manifold and reforming chamber, combined with catalyst optimization and plasma-assisted methods. Furthermore, it comprehensively improves engine combustion efficiency, power performance, and environmental performance through intelligent ignition and adaptive switching of combustion modes.

[0008] This invention provides a two-stage hydrogen-ammonia reforming system for a four-stroke / six-stroke engine with dynamic switching, including a cylinder head, a cylinder block and a two-stage hydrogen-ammonia reforming system, wherein the two-stage hydrogen-ammonia reforming system includes a primary reforming unit, a combustion control unit and a secondary reforming gas storage unit.

[0009] The cylinder head top is provided with an exhaust valve, an intake valve, a spark plug, and a secondary reforming unit;

[0010] The end of the injector is connected to the air intake duct. The injector injects ammonia fuel, which mixes with the air in the air intake duct to form an ammonia-air mixture. The primary reforming unit is located in the air intake duct and below the injector.

[0011] The primary reforming unit has a built-in heating function and its surface is provided with a catalyst layer for catalyzing ammonia reforming; the ammonia-air mixture that has passed through the primary reforming unit is initially reformed to form an ammonia-hydrogen-air mixture.

[0012] The secondary reforming gas storage unit includes a reforming chamber and a gas storage valve. The inner surface of the reforming chamber has a catalyst layer for catalyzing ammonia reforming, which is used to reform the mixed gas from the fuel chamber to generate a hydrogen-rich mixed gas, thus completing the staged storage and release of energy.

[0013] The mixture stored and reformed in the combustion chamber at the end of the first compression stroke is released back into the combustion chamber after the first exhaust stroke.

[0014] The combustion control unit is used to dynamically adjust the four-stroke or six-stroke mode according to the engine load, and to adjust the opening / closing of the intake valve, exhaust valve, and gas storage valve, as well as the ignition timing of the spark plugs and the injection timing of the injectors using the ECU.

[0015] In one embodiment of a marine engine application, the secondary reforming gas storage unit has a built-in heating function and an inner surface with a catalyst layer for catalytic ammonia reforming, wherein the catalyst layer is a non-metallic catalyst. Preferably, the active component of the catalyst in the catalyst layer is selected from one or more of the following: boron, carbon, ruthenium, nickel, iron, and cobalt.

[0016] In one embodiment of an in-vehicle infotainment system, the secondary reforming gas storage unit is a plasma reactor, and the inner surface of the plasma reactor has a catalyst layer for catalyzing ammonia reforming, and the catalyst layer is a metal catalyst.

[0017] Furthermore, the inner surface of the reforming chamber has a microrib structure to enhance the contact area between the gas and the catalyst.

[0018] Preferably, the microrib structure is a continuous or discontinuous raised / recessed rib. Of course, depending on the specific application, the internal wall surface can be designed differently. The microrib structure can be a continuous spiral, parallel straight ribs, or discrete nail-like, scale-like, or wavy shape. Furthermore, the cross-sectional shape of the microrib can be rectangular, triangular, trapezoidal, or semi-circular. A streamlined semi-circular or trapezoidal cross-section is preferred to reduce flow resistance and avoid stress concentration.

[0019] Furthermore, the intake duct is connected to the intake valve, through which air is injected into the combustion chamber. The intake valve is opened by the combustion control unit during the intake stroke to allow air to enter the combustion chamber; it remains closed during the compression, combustion, and exhaust phases.

[0020] Furthermore, the primary reforming unit is a reforming mesh, which employs an electrically heated structure and is coated with a Ru-Ni catalyst.

[0021] Furthermore, the primary reforming unit comprises multiple layers of stacked reforming networks, which are rotated sequentially from top to bottom by a certain angle. Each reforming grid is rotated relative to the reforming grid above it by an angle. .

[0022] The combustion strategy of the hydrogen-ammonia two-stage reforming system in the four-stroke / six-stroke dynamically switching engine includes:

[0023] The cycle mode and hydrogen function are dynamically adjusted according to the real-time load zone of the engine.

[0024] When the engine load is in the low load range of 0% to 20%, the engine is controlled to adopt a four-stroke cycle mode and a high-energy ignition method is activated so that the hydrogen in the ammonia-hydrogen-air mixture generated by the primary reforming unit is used as the main ignition source to ignite in the cylinder to stabilize combustion.

[0025] When the engine load is in the low to medium load range of 20% to 40%, the engine is controlled to maintain a four-stroke cycle mode, so that the hydrogen in the mixture is used as an auxiliary combustion stabilizer to support the continuous combustion of ammonia.

[0026] When the engine load is in the medium-high load range of 40% to 100%, the engine is controlled to switch from the four-stroke cycle mode to the six-stroke cycle mode, and the high-frequency low-voltage pulse ignition mode is activated. In the second stroke stage, the ammonia is deeply decomposed using the secondary reforming gas storage unit. In the fourth stroke stage, the hydrogen-rich mixture in the secondary reforming gas storage unit is added to the cylinder, and the high combustion rate of hydrogen is used to compensate for the insufficient energy release when ammonia is used as the main fuel.

[0027] Furthermore, the operation process of the four-stroke cycle mode includes:

[0028] During the first stroke intake and primary reforming stage, the heated reforming grid is activated, the intake valve is opened, and the ammonia fuel from the injector mixes with the air in the intake manifold 8. After preliminary reforming by the primary reforming unit, an ammonia-hydrogen-air mixture is formed and enters the combustion chamber; the piston 6 moves downward; at this time, the exhaust valve and the gas storage valve remain closed.

[0029] During the compression phase of the second stroke, the piston moves upward from the bottom dead center, compressing the gas-fuel mixture in the combustion chamber;

[0030] During the third stroke's combustion and power phase, the spark plug ignites the gas-fuel mixture in the combustion chamber, pushing the piston down from top dead center to complete the combustion and power process.

[0031] During the fourth stroke exhaust phase, the piston moves upward from the bottom dead center, opening the exhaust valve. After exhausting, the exhaust valve closes, thus completing a full four-stroke cycle.

[0032] Furthermore, the operation process of the six-stroke cycle mode includes:

[0033] During the first stroke intake and primary reforming stage, the heated reforming grid is activated, the intake valve is opened, and the ammonia fuel from the injector mixes with the air in the intake manifold. After preliminary reforming by the primary reforming unit, an ammonia-hydrogen-air mixture is formed and enters the combustion chamber; the piston moves downward; at this time, the exhaust valve and the gas storage valve remain closed.

[0034] During the second stroke compression and secondary reforming stage, the piston moves upward from the bottom dead center, compressing the gas mixture in the combustion chamber. Before the piston approaches the top dead center, the gas storage valve is opened, allowing some of the high-temperature and high-pressure gas to be introduced into the reforming chamber for storage and secondary reforming. Then the gas storage valve is closed. The gas mixture from the combustion chamber completes the deep decomposition of ammonia in the reforming chamber.

[0035] During the ignition and first combustion power stage of the third stroke, the spark plug discharges and ignites at the end of the compression, igniting the mixture in the combustion chamber; pushing the piston down from top dead center to complete the combustion power process;

[0036] During the first exhaust phase of the fourth stroke, the piston moves upward from the bottom dead center and opens the exhaust valve; after exhaust is completed, the exhaust valve closes and the gas storage valve opens, releasing the mixture from the reforming chamber back into the combustion chamber to form a new combustible gas environment;

[0037] During the second combustion power phase of the fifth stroke, the piston continues to move upward, compressing the air-fuel mixture from the reforming chamber; when the piston approaches top dead center, the spark plug discharges again, igniting the combustible mixture in the combustion chamber and initiating the second combustion; then the piston moves downward again to complete the second combustion power phase.

[0038] During the second exhaust phase of the sixth stroke, the piston moves upward again from the bottom dead center, opening the exhaust valve and releasing the exhaust gases after the second combustion.

[0039] The beneficial effects of this invention are as follows:

[0040] This invention constructs a hydrogen-ammonia two-stage reforming path by implementing primary reforming through a reforming mesh in the intake manifold and secondary deep reforming in a secondary reforming storage unit on the cylinder head. This design can provide a hydrogen-rich mixture under all operating conditions, not only improving the problems of high ignition energy and slow flame propagation speed of ammonia fuel, but also effectively improving fuel decomposition rate and combustion completeness. Compared with traditional single-stage reforming, this invention achieves dual ignition and dual power output per unit cycle, significantly improving thermal efficiency and energy conversion efficiency, and solving the technical bottleneck of incomplete combustion of ammonia fuel.

[0041] Furthermore, this invention incorporates a collaborative design between the gas storage valve and the reforming chamber in the secondary reforming gas storage unit. This allows for the temporary storage of some high-temperature, high-pressure gases, which are then released at appropriate times, forming a secondary combustion process and ensuring stable engine operation under various load conditions. In marine applications, non-metallic catalysts and resistance wire temperature compensation are used to ensure stable hydrogen production at low speeds. In automotive applications, metallic catalysts combined with plasma discharge are used to achieve rapid hydrogen production under high-speed transient conditions. This differentiated design meets the requirements of long-term high-load marine engines and rapid dynamic response automotive engines, significantly improving the continuity and reliability of power output. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a single-cylinder structure of the marine four-stroke / six-stroke dynamically switching engine in Example 1;

[0043] Figure 2 yes Figure 1 The diagram shows a primary reforming unit in the intake manifold of the engine.

[0044] Figure 3 This is a schematic diagram of the reforming chamber of a marine four-stroke / six-stroke dynamically switching engine as shown in Example 1.

[0045] Figure 4 This is a schematic diagram of the reforming network layout of the primary reforming unit of a marine four-stroke / six-stroke dynamically switching engine, as shown in Example 1. The three reforming networks on the left side of the diagram represent n reforming networks stacked together, with each stacked network rotated a certain angle from top to bottom. The right side of the diagram shows an exploded view of the superimposed reforming networks.

[0046] Figure 5 This is a comparison diagram of the combustion control strategies for four-stroke and six-stroke engines in the intelligent operation method of the hydrogen-ammonia two-stage reforming system of the marine four-stroke / six-stroke dynamically switching engine.

[0047] Figure 6 This is a schematic diagram of the reforming chamber of a vehicle engine with dynamic switching between four-stroke and six-stroke strokes, as shown in Example 2.

[0048] Among them, 1: exhaust passage; 2: exhaust valve; 3: reforming chamber; 4: spark plug; 5: air reservoir valve; 6: piston; 7: intake valve; 8: intake passage; 9: reforming mesh; 10: injector. Detailed Implementation

[0049] To make the objectives, technical solutions, beneficial effects, and significant advancements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings provided in the examples of the present invention. Obviously, all the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In the description of this application, unless otherwise expressly specified and limited, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more; unless otherwise specified or explained, the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0051] Example 1

[0052] like Figure 1As shown, a marine four-stroke / six-stroke dynamically switching engine includes a cylinder head, cylinder block, and a hydrogen-ammonia two-stage reforming system. The hydrogen-ammonia two-stage reforming system includes a primary reforming unit, a combustion control unit, and a secondary reforming gas storage unit.

[0053] The cylinder block has a cylindrical structure and contains a piston 6. The piston 6 reciprocates along the cylinder block axis to realize the basic cycle processes of intake, compression, combustion, and exhaust. It performs two power strokes during its downward movement and sequentially performs compression and exhaust during its upward movement, converting the energy released by combustion into mechanical energy output. The space formed by the cylinder head, cylinder block, and piston 6 constitutes the combustion chamber. The top of the cylinder head is equipped with an exhaust valve 2, an intake valve 7, a spark plug 4, and a secondary reforming unit. The bottom of the spark plug 4 extends into the combustion chamber to ignite the air-fuel mixture in the cylinder. The spark plug 4 is installed in the center of the cylinder head and performs discharge ignition at the end of the first compression and at the end of the second compression after the release of stored gas (during the six-stroke process), achieving two combustion processes.

[0054] The intake manifold 8 is connected to the intake valve 7, through which air is injected into the combustion chamber. During the intake stroke, the intake manifold 8 is opened by the combustion control unit to allow air to enter the combustion chamber; during the compression, combustion, and exhaust phases, it remains closed to ensure cylinder sealing and complete combustion. Furthermore, the upper end of the intake manifold 8 is equipped with an injector 10 and a primary reforming unit.

[0055] like Figure 2 , Figure 4 As shown, the primary reforming unit is a multi-layered reforming mesh 9 fixedly mounted on the intake duct. The primary reforming unit is located below the injector 10 and at approximately 2 / 3 of the total length of the intake duct 8 (starting from the intake valve). The reforming mesh 9 employs an electrically heated structure and is coated with a Ru-Ni catalyst. Figure 4 As shown, the primary reforming unit includes n layers of reforming networks 9, which are rotated sequentially from top to bottom by a certain angle. Each reforming mesh 9 is rotated relative to the reforming mesh above it by an angle. The reforming mesh is made of metal and heats up when connected to an external power source to assist the catalytic reforming process.

[0056] When the intake valve is open, the injector 10 injects ammonia fuel into the intake manifold. After the ammonia fuel mixes with air, it undergoes a reforming process through the reforming screen 9. The catalyst on the heated reforming screen 9 works synergistically with the thermal effect to cause some ammonia molecules in the ammonia-air mixture to undergo preliminary decomposition, releasing a certain amount of hydrogen gas, thereby improving combustion characteristics.

[0057] The secondary reforming gas storage unit includes a reforming chamber 3 and a gas storage valve 5, such as Figure 1The reforming chamber 3 shown is connected to the combustion chamber via a pipeline, and a gas storage valve 5 is also installed on the pipeline leading to the cylinder block to control whether the air-fuel mixture enters the combustion chamber. Specifically, the gas storage valve 5 opens at the end of the first compression stroke, forcing a portion of the high-temperature, high-pressure mixture into the gas storage chamber for storage; it reopens after the first exhaust stroke, releasing the stored gas back into the combustion chamber to provide energy for secondary combustion. The reforming chamber 3 is also connected to the intake unit via a pipeline, used to perform secondary ammonia decomposition on the ammonia-containing mixture from the combustion chamber under the high-temperature, high-pressure environment generated by the engine, generating more hydrogen and directly introducing the hydrogen-rich mixture into the combustion chamber. The gas storage valve 5 is regulated by the combustion control unit during the compression, combustion, and exhaust phases to ensure orderly gas flow.

[0058] like Figure 3 As shown, the reforming chamber is a high-temperature and high-pressure resistant structure, a three-layer composite structure comprising, from the outside in, a substrate layer, a heating layer, and a catalyst layer. The substrate layer is made of high-strength austenitic stainless steel to withstand an internal pressure of 20 MPa. The heating layer, made of a nickel-based alloy, is fixed to the inner surface of the substrate layer and contains a resistance wire that is spirally and continuously wound around the heating layer and connected to an external power source. A catalyst layer, a sprayed non-metallic BC-based catalyst, is coated on the inner surface of the heating layer for the reforming reaction. The active components of the catalyst include boron and carbon, which exist in nanoparticle form and are coated on the inner wall to provide maximum specific surface area, supplemented by resistance wire heating compensation during use.

[0059] Furthermore, the wall of the reforming chamber is optimized and processed into a micro-rib structure. The micro-rib structure is a continuous spiral rib with a triangular cross-section, which enhances the contact area between the gas and the catalyst, allowing the mixed gas to have a longer residence time in the reforming chamber, thereby achieving efficient cracking of ammonia.

[0060] Because marine engines operate at low speeds and have long gas residence times, this method ensures efficient ammonia decomposition and stable hydrogen production over extended periods.

[0061] In this invention, the first-stage reforming efficiency Mainly affected by the number of network layers Weak current intensity and ammonia concentration The influence of this. To describe its nonlinearity and parameter coupling, this invention establishes the following model using a complete quadratic function form:

[0062]

[0063] in: : First-stage reforming efficiency (%) Number of reforming network layers; : Weak current intensity (A); : Inlet ammonia concentration (volume fraction, %); : Regression coefficients, obtained from experimental fitting or numerical calculation.

[0064] Similarly, the efficiency of quadratic reorganization It is mainly affected by the following parameters:

[0065] : Heating resistance wire temperature (K or °C); Ammonia concentration in the cylinder (volume fraction, %); Cylinder pressure (MPa); : In-cylinder gas temperature (K or °C); : Fin heat transfer influence coefficient (taking into account fin height, arrangement, heat transfer coefficient, etc., and treated as dimensionless).

[0066] To characterize the nonlinearity and coupling effects among the parameters, this invention establishes the following complete quadratic function model:

[0067]

[0068] in, Secondary reforming efficiency (ammonia decomposition rate or hydrogen production rate, %) Undetermined regression coefficients can be obtained through experimental determination or numerical simulation fitting.

[0069] An exhaust passage 1 is provided at exhaust valve 2, which opens during the exhaust stroke to discharge the exhaust gas after combustion from the cylinder, ensuring the continuity of cylinder circulation and combustion stability.

[0070] The combustion control unit is used to dynamically adjust the ignition mode according to the engine load: under low load, a four-stroke cycle combined with high-energy ignition is used to stabilize combustion; under high load, it switches to a six-stroke cycle and uses high-frequency low-pressure pulse ignition to enhance power output and suppress knock. In specific control, the ECU adjusts the opening / closing of the intake valve, exhaust valve, and gas storage valve 5, the ignition timing of the spark plug and the injection timing of the injector 10, as well as the heating timing of the resistance wire of the first reforming unit and the second reforming gas storage unit.

[0071] This invention achieves fuel and air preparation and primary reforming through intake duct 8, injector 10 and reforming mesh 9, secondary high-efficiency reforming through reforming chamber 3, dual ignition and dual combustion through spark plug 4, staged energy storage and release through second reforming gas storage unit, and finally, the piston performs two power strokes and the exhaust valve discharges exhaust gas, thus forming a two-stage reforming, six-stroke cycle high-efficiency combustion system.

[0072] The operation process of the hydrogen-ammonia two-stage reforming system for the marine four-stroke / six-stroke dynamically switching engine includes:

[0073] At low loads, a four-stroke cycle combined with high-energy ignition is used to stabilize combustion. The specific operating process includes:

[0074] In the first stroke intake and primary reforming stage, the heated reforming screen 9 is activated, and the intake valve 7 is opened, allowing air to enter the intake manifold 8. The injector 10 injects a measured amount of ammonia fuel into the intake manifold 8. After mixing with the air in the intake manifold 8, the ammonia fuel passes through the heated reforming screen 9 arranged within the intake manifold. The catalyst on the reforming screen 9, in conjunction with thermal action, causes some ammonia molecules in the ammonia-air mixture to undergo preliminary decomposition to form hydrogen, creating a premixed ammonia-hydrogen-air mixture. The hydrogen-rich ammonia-hydrogen-air mixture enters the combustion chamber through the intake valve 7. The piston 6 moves downward from top dead center, drawing in sufficient fresh mixture to provide the necessary conditions for the subsequent two combustion cycles. At this time, the exhaust valve 2 and the gas storage valve 5 remain closed to prevent gas leakage and ensure cylinder charging efficiency. Although the intake temperature is low at this stage and the primary reforming efficiency is limited, it effectively reduces the difficulty and energy consumption of subsequent deep reactions, serving as a pretreatment process.

[0075] During the compression phase of the second stroke, piston 6 moves upward from bottom dead center, compressing the gas mixture in the combustion chamber and causing the pressure and temperature in the combustion chamber to gradually increase.

[0076] During the third stroke's combustion and power phase, the spark plug ignites the gas-fuel mixture in the combustion chamber; the high-temperature, high-pressure gas produced by combustion expands rapidly, pushing piston 6 downward from top dead center to complete the combustion and power process.

[0077] During the fourth stroke exhaust phase, piston 6 moves upward from bottom dead center, opening exhaust valve 2 to completely expel the combusted exhaust gas from the cylinder. After exhaust is complete, exhaust valve 2 is closed, thus forming a complete four-stroke cycle.

[0078] Under high load, the system switches to a six-stroke cycle and uses high-frequency, low-voltage pulse ignition. The specific operating process includes:

[0079] In the first stroke intake and primary reforming stage, the heating reforming mesh 9 and the resistance wire of the heating reforming chamber 3 are activated, and the intake valve 7 is opened to allow air to enter the intake manifold 8. The injector 10 injects a fixed amount of ammonia fuel (the amount of ammonia fuel injected) into the intake manifold 8. The ammonia fuel mixes with the air in the intake manifold 8 to form a premixed ammonia-air mixture. Subsequently, the heated reforming mesh 9 arranged in the intake manifold, with the catalyst on the reforming mesh 9 acting synergistically with the heat, causes some ammonia molecules in the ammonia-air mixture to undergo preliminary decomposition to form hydrogen. The hydrogen-rich mixture enters the combustion chamber through the intake valve 7. The piston 6 moves downward from top dead center, drawing in sufficient fresh mixture to provide the necessary conditions for the subsequent two combustion cycles. At this time, the exhaust valve 2 and the gas storage valve 5 remain closed to prevent gas leakage and ensure cylinder charging efficiency. Although the intake temperature is low at this stage and the primary reforming efficiency is limited, it effectively reduces the difficulty and energy consumption of subsequent deep reactions, serving as a pretreatment process.

[0080] During the second stroke compression and secondary reforming stage, piston 6 moves upward from bottom dead center, compressing the gas mixture in the combustion chamber and gradually increasing the pressure and temperature in the combustion chamber. Before piston 6 approaches top dead center, gas storage valve 5 is opened, allowing some high-temperature and high-pressure gas to be introduced into reforming chamber 3 for storage and secondary reforming. Then, gas storage valve 5 is closed. The gas mixture from the combustion chamber completes the deep decomposition of ammonia in reforming chamber 3.

[0081] During the ignition and first combustion power stage of the third stroke, spark plug 4 discharges and ignites at the end of compression, igniting the mixture in the combustion chamber; the high-temperature and high-pressure gas generated by combustion expands rapidly, pushing piston 6 down from top dead center to complete the first combustion power process; at this time, intake valve 7, exhaust valve 2 and gas storage valve 5 are all in the closed state, so that the combustion process is in a completely closed environment, ensuring complete combustion of fuel and maximum energy release.

[0082] During the first exhaust phase of the fourth stroke, piston 6 moves upward from bottom dead center, opening exhaust valve 2; the exhaust gas produced in the first combustion is discharged from the combustion chamber through exhaust passage 1. When exhaust is nearly complete, exhaust valve 2 is closed, and gas storage valve 5 is opened, releasing the high-energy mixture stored in reforming chamber 3 back into the combustion chamber, forming a new combustible gas environment, providing additional energy input for the second compression and combustion process.

[0083] During the second combustion power phase of the fifth stroke, piston 6 continues to move upward, compressing the air-fuel mixture from reforming chamber 3. When piston 6 approaches top dead center, spark plug 4 discharges again, igniting the combustible mixture in the combustion chamber and initiating a second combustion. The high-temperature, high-pressure gas generated by combustion pushes the piston downward again, completing the second combustion power phase. At this time, intake valve 7, exhaust valve 2, and gas storage valve 5 remain closed to ensure combustion stability and energy utilization.

[0084] In the second exhaust phase of the sixth stroke, piston 6 moves upward again from bottom dead center, opening exhaust valve 2 to completely expel the exhaust gas after the second combustion from the cylinder. After exhaust is completed, exhaust valve 2 is closed, thus forming a complete six-stroke cycle.

[0085] The exhaust valve remains closed during non-exhaust phases to ensure cylinder sealing and combustion integrity.

[0086] Based on the engine load, the following operating process is executed: Four-stroke and six-stroke combustion control strategies, for example... Figure 5 As shown:

[0087] In the 0–20% low-load range, the engine operates in a four-stroke cycle. At this point, power demand is low, intake air volume is low, and cylinder temperature is insufficient. Simply injecting ammonia fuel, due to its high ignition energy and slow flame propagation speed, can easily lead to ignition failure. Therefore, it is necessary to maintain a high hydrogen conversion rate, utilizing the low ignition energy and high propagation speed characteristics of hydrogen, combined with a high-energy ignition strategy, to rapidly form a stable flame core in the lean ammonia-hydrogen mixture, ensuring smooth combustion start-up while avoiding localized over-rich combustion and flameout.

[0088] In the 20–40% low-load range, the cylinder temperature gradually increases, combustion conditions improve, and the engine maintains a four-stroke cycle. At this time, the ammonia injection rate increases with load, and combustion shifts from "ignition-driven" to "stable exothermic combustion." The role of hydrogen transitions from primary ignition to auxiliary combustion, and its conversion rate gradually decreases with increasing load. During this stage, the combustion environment established by hydrogen allows ammonia to sustain flame propagation autonomously, reducing hydrogen consumption and lowering NOx emissions caused by high-hydrogen combustion. x Emissions, achieving a balance between economic efficiency and environmental protection.

[0089] In the 40–100% medium-high load range, the engine switches to a six-stroke cycle mode to meet the strong power demand. Due to the low calorific value of ammonia fuel limiting energy release, hydrogen transitions from ignition assistance to power compensation during this phase, with the conversion rate significantly increasing with load to compensate for the insufficient ammonia energy. The ignition method simultaneously switches to high-frequency, low-pressure pulse discharge, replacing the single high-energy ignition of the four-stroke cycle. This ensures stable ignition of the high-hydrogen-ammonia mixture while preventing localized knocking, keeping the maximum cylinder pressure below 20 MPa. Thus, the dual goals of "high power output + safe combustion" are achieved under high load.

[0090] The intelligent operation method of the hydrogen-ammonia two-stage reforming system for a marine four-stroke / six-stroke dynamically switching engine described in this invention uses a digital twin model to map, simulate, monitor, and predict the state, performance, and behavior of the six-stroke engine throughout its entire lifecycle. With the ECU as the core, and in conjunction with sensors such as pressure, temperature, and flow, real-time sensor data is transmitted and mapped to the virtual model for trend judgment and fault prediction. Through dynamic control of key actuators such as the intake valve, exhaust valve, gas storage valve, and injector 10, optimal matching of combustion timing, precise adjustment of the hydrogen-ammonia ratio, and second-level fault response are achieved, ensuring stable and efficient engine operation under all operating conditions.

[0091] Example 2

[0092] A vehicle-mounted four-stroke / six-stroke dynamically switching engine includes a cylinder head, cylinder block, and a hydrogen-ammonia two-stage reforming system. The hydrogen-ammonia two-stage reforming system includes a primary reforming unit, a combustion control unit, and a secondary reforming gas storage unit. This embodiment is for use in an automotive engine and is similar to Embodiment 1; only the differences are described below.

[0093] The secondary reforming gas storage unit includes a reforming chamber 3 and a gas storage valve 5, such as Figure 6 As shown, the reforming cavity 3 has the same structure as in Example 1, and is still a three-layer composite structure.

[0094] Unlike Example 1, the reforming chamber 3 does not contain a resistance wire. Instead, it contains a Ru-Ni metal catalyst and a coaxial cylindrical plasma reactor (DBD reactor). A metal rod serves as the central high-voltage electrode, surrounded by an insulator. The inner wall of the reforming chamber 3 acts as a grounding electrode. The plasma reactor is connected to an external high-voltage power supply for energy input. Upon energization, an arc discharge occurs between the electrodes, generating a high-energy electron flow that breaks the chemical bonds of ammonia molecules, forming highly active plasma. Under the action of the catalyst, this plasma accelerates the hydrogen generation process, meeting the high-speed, short-time combustion requirements of automotive engines.

[0095] The reforming chamber of the vehicle engine is a high-temperature and high-pressure resistant structure. The reforming chamber is a three-layer composite structure, which includes a base layer, a heating layer and a catalyst layer from the outside to the inside. The base layer is made of high-strength austenitic stainless steel to withstand the internal pressure of 3MPa.

[0096] The spark plugs in the engine use high-frequency, low-pressure pulse ignition to avoid knocking and improve combustion stability.

[0097] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A hydrogen-ammonia dual-stage reforming system for a four-stroke / six-stroke dynamically-switched engine, characterized by The cylinder head, the cylinder block and the hydrogen-ammonia two-stage reforming system, the hydrogen-ammonia two-stage reforming system comprising a primary reforming unit, a combustion control unit and a secondary reforming gas storage unit; The top of the cylinder head is provided with an exhaust valve (2), an intake valve (7), a spark plug (4) and a secondary reforming unit; The end of the injector (10) is connected to the intake port (8), the injector (10) injects ammonia fuel, mixes with air in the intake port to form ammonia-air mixture; the primary reforming unit is arranged in the intake port (8) and below the injector (10); The primary reforming unit has a built-in heating function, and the surface is provided with a catalyst layer for catalyzing ammonia gas reforming; the primary reforming unit preliminarily reforms the ammonia-air mixture to form ammonia-hydrogen-air mixture; The secondary reforming gas storage unit comprises a reforming cavity (3) and a gas storage valve (5), the inner surface of the reforming cavity (3) has a catalyst layer for catalyzing ammonia gas reforming, which is used to reform the mixture from the fuel chamber to generate hydrogen-rich mixture, and complete the phased storage and release of energy; The mixture in the combustion chamber is stored and reformed at the end of the first compression stroke, and the generated hydrogen-rich mixture is released back to the combustion chamber after the first exhaust is completed; The combustion control unit is used to dynamically adjust the four-stroke or six-stroke mode according to the engine load, and adjust the opening / closure of the intake valve, the exhaust valve and the gas storage valve (5) by ECU, the ignition time of the spark plug and the injection time of the injector (10).

2. The hydrogen-ammonia dual-stage reforming system for a four-stroke / six- stroke dynamically-switching engine of claim 1, wherein, In the application of marine engine, the secondary reforming gas storage unit has a built-in heating function, and the inner surface has a catalyst layer for catalyzing ammonia gas reforming, and the catalyst layer adopts a non-metal catalyst.

3. The hydrogen-ammonia dual stage reforming system for four-stroke / six- stroke dynamically switched engine of claim 2, wherein, The active component of the catalyst of the catalyst layer is selected from one or more of boron, carbon, ruthenium, nickel, iron, cobalt.

4. The hydrogen-ammonia dual stage reforming system for four-stroke / six- stroke dynamically switched engine of claim 1, wherein, In the application of vehicle engine, the secondary reforming gas storage unit is in a plasma reactor, the inner surface of the plasma reactor has a catalyst layer for catalyzing ammonia gas reforming, and the catalyst layer adopts a metal catalyst.

5. The hydrogen-ammonia dual-stage reforming system for a four-stroke / six- stroke dynamically-switching engine according to claim 2 or 4, characterized in that, The inner surface of the reforming cavity (3) has a micro-rib structure.

6. The hydrogen-ammonia dual stage reforming system for four-stroke / six- stroke dynamically switched engine of claim 5, wherein, The micro-rib structure is a continuous or intermittent convex / concave rib part.

7. The hydrogen-ammonia dual stage reforming system for four-stroke / six- stroke dynamically switched engine of claim 1, wherein, The primary reforming unit is a reforming net (9), the reforming net (9) adopts an electric heating structure, and the surface is coated with Ru-Ni catalyst.

8. The hydrogen-ammonia dual stage reforming system for four-stroke / six- stroke dynamically switched engine of claim 7, wherein, The primary reforming unit comprises a plurality of superimposed reforming nets (9), and the plurality of reforming nets (9) are rotated by a certain angle from top to bottom, and each reforming net (9) is rotated by a certain angle relative to the reforming net above it.

9. The hydrogen-ammonia dual stage reforming system for four-stroke / six- stroke dynamically switched engine of claim 1, wherein, The combustion strategy of the hydrogen-ammonia two-stage reforming system comprises: According to the real-time load partition of the engine, the cycle mode and hydrogen function are dynamically adjusted; When the engine load is in the low load range of 0% to 20%, the engine is controlled to adopt the four-stroke cycle mode, and the high-energy ignition mode is enabled, so that the hydrogen in the ammonia-hydrogen-air mixture generated by the primary reforming unit is ignited as the main ignition source in the cylinder to stabilize the combustion; When the engine load is in the medium-low load range of 20% to 40%, the engine is controlled to maintain the four-stroke cycle mode, so that the hydrogen in the mixture acts as an auxiliary stable combustion medium to support the continuous combustion of ammonia gas; When the engine load is in the middle and high load range of 40% to 100%, the engine is switched from the four-stroke cycle mode to the six-stroke cycle mode, and the high-frequency low-voltage pulse ignition mode is enabled, the deep decomposition of ammonia is carried out by the secondary reforming gas storage unit in the second stroke stage, and the hydrogen-rich gas in the secondary reforming gas storage unit is supplemented into the cylinder in the fourth stroke stage, and the high combustion rate of hydrogen is used to compensate for the insufficient energy release of ammonia as the main fuel.

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