Engine combustion system and method of controlling the same

Abstract

The present application belongs to the technical field of engine, and particularly relates to an engine combustion system and a control method thereof. The engine combustion system comprises a cylinder and a jet ignition device. The cylinder comprises a main combustion chamber. The jet ignition device comprises a shell, the shell is provided with an ignition chamber and a spray hole, the ignition chamber is communicated with the main combustion chamber of the cylinder through the spray hole, the spray hole comprises a first spray hole and a second spray hole, the first spray hole and the second spray hole are respectively communicated with the ignition chamber and the main combustion chamber; the inner diameter of the first spray hole gradually decreases along the direction from the inlet of the first spray hole to the outlet of the first spray hole; the inner diameter of the second spray hole gradually increases along the direction from the inlet of the second spray hole to the outlet of the second spray hole; the inlet inner diameter of the first spray hole at the inlet of the first spray hole is smaller than the inlet inner diameter of the second spray hole at the inlet of the second spray hole. By using the engine combustion system in the technical solution, the jet penetration and the flame energy density can be simultaneously improved, so that the jet ignition efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of engine technology, specifically relating to an engine combustion system and its control method. Background Technology

[0002] In existing ignition chamber jet ignition technology, the propagation characteristics of the jet flame after entering the main combustion chamber from the ignition chamber nozzle are mainly governed by two key parameters: jet velocity and jet energy, both determined by the nozzle diameter. Jet velocity directly affects the penetration ability of the flame jet, the intensity of induced turbulence, and the entrainment and mixing effect on the surrounding mixture, while jet energy determines the flame volume, temperature level, and the sustained combustion capability of the ignition flame core. However, in actual structural design, while increasing the nozzle diameter can increase the total energy carried per unit jet, it also leads to a decrease in the Mach number and momentum flux at the jet exit, resulting in a lower jet velocity and a contraction of the jet core region, thereby weakening the jet's longitudinal penetration ability and flame propagation capability within the cylinder. Conversely, when a smaller nozzle diameter is used to obtain higher injection velocity and stronger jet momentum, the heat release capacity per unit jet and the flame volume are limited, easily leading to insufficient ignition flame core energy. Because of the structural constraints between the aforementioned velocity and energy indicators, existing ignition chamber designs often have to compromise between the two in engineering applications. This results in a design pattern where the nozzle diameter is relatively uniform and the number and direction of the nozzles are approximately symmetrically distributed. Consequently, the jet flame exhibits a generally uniform spatial energy distribution after entering the main combustion chamber, lacking the ability to differentiate and enhance key fuel-rich areas or lean-mixed areas.

[0003] Under ammonia fuel conditions, the evaporation of liquid ammonia in the cylinder absorbs a large amount of latent heat of vaporization, causing a significant drop in the temperature of the air-fuel mixture at the end of compression. This easily leads to the formation of regions with lower temperatures and weaker chemical reactivity within the cylinder. Furthermore, influenced by injection timing and airflow organization, a stratified mixing structure with uneven stoichiometry and locally high or low fuel concentrations can also occur. Against this backdrop, the aforementioned ignition chamber structure of "symmetrical aperture + uniform jet distribution" struggles to provide targeted compensation for the fuel state in different regions: on the one hand, high fuel concentration regions fail to obtain a sufficiently concentrated and high-momentum jet flame to quickly establish a strong flame core; on the other hand, regions with lower temperatures or lower stoichiometry lack sustained energy-supported flame jet coverage, resulting in a spatially significant lag and unevenness in early combustion development. This structural constraint is particularly pronounced under conditions such as cold start, low temperature environment, and lean combustion. Due to the further enhancement of the temperature drop effect by the latent heat of liquid ammonia vaporization, the overall in-cylinder reactivity decreases. Furthermore, the jet velocity and jet energy are limited by the compromise design, making it difficult to simultaneously ensure jet penetration and flame energy density under the above conditions. This manifests in operating phenomena such as increased ignition delay time, slowed initial combustion rate, and decreased inter-cycle combustion stability. To a certain extent, this limits the performance potential and operational adaptability of this type of ignition chamber jet ignition technology in ammonia fuel engines.

[0004] Therefore, there is an urgent need to provide an engine combustion system and its control method to solve the above problems. Summary of the Invention

[0005] The objective of this invention is to solve at least the problem of how to simultaneously improve jet penetration and flame energy density, thereby increasing jet ignition efficiency. This objective is achieved through the following technical solution: A first aspect of the present invention provides an engine combustion system comprising: A cylinder, the cylinder including a main combustion chamber; A jet ignition device, comprising a housing, wherein the housing is provided with an ignition chamber and a nozzle, the nozzle comprising a first nozzle and a second nozzle, the first nozzle and the second nozzle each being connected to the ignition chamber and the main combustion chamber; Along the direction from the inlet to the outlet of the first nozzle, the inner diameter of the first nozzle gradually decreases. Along the direction from the inlet to the outlet of the second nozzle, the inner diameter of the second nozzle gradually increases; The inner diameter of the inlet of the first nozzle at the entrance of the first nozzle is smaller than the inner diameter of the inlet of the second nozzle at the entrance of the second nozzle.

[0006] In traditional structural designs, the nozzle orifice diameter is uniform, making it difficult to simultaneously meet the demands of high-speed, concentrated jets in the initial ignition phase and the need for wide-area, high-flow-rate jets in the later stages of flame development. This technical solution employs a gradient design for the nozzle size in the ignition chamber of the engine combustion system. The small-diameter first nozzle uses a tapering structure, generating a high-velocity, high-momentum flame jet through throat acceleration, effectively improving jet penetration, significantly expanding the effective ignition area, and increasing in-cylinder turbulence intensity. The large-diameter second nozzle uses a expanding structure, allowing the flame jet to achieve stable expansion and energy release after exiting the nozzle, thereby enhancing overall ignition energy and reducing the risk of flame quenching. Thus, by combining nozzles of different diameters, the first nozzle is responsible for ignition reliability, while the second nozzle is responsible for combustion speed and safety; the two complement each other, providing wider fuel adaptability without altering the combustion system hardware.

[0007] In addition, the engine combustion system of the present invention may also have the following additional technical features: In some embodiments of the present invention, the angle between the injection direction of the first nozzle and the axis of the ignition chamber is 25° to 35°.

[0008] In some embodiments of the present invention, the angle between the injection direction of the second nozzle and the axis of the ignition chamber is 55° to 65°.

[0009] In some embodiments of the present invention, the plurality of nozzles are arranged in a spiral pattern around the central axis of the ignition chamber.

[0010] In some embodiments of the present invention, the engine combustion system further includes an air intake, a low-pressure ammonia injector, and a liquid ammonia high-pressure injector. One end of the air intake is connected to an external air source, and the other end of the air intake is connected to the main combustion chamber. The low-pressure ammonia injector is disposed on the air intake and is used to inject gaseous ammonia into the air intake. The liquid ammonia high-pressure injector is used to inject liquid ammonia into the main combustion chamber.

[0011] In some embodiments of the present invention, a plurality of liquid ammonia high-pressure injectors are provided, and the plurality of liquid ammonia high-pressure injectors are arranged at equal intervals along the circumferential direction of the jet ignition device.

[0012] In some embodiments of the present invention, the housing is provided with a plurality of first spray holes and two second spray holes on the side facing the liquid ammonia high-pressure injector, and the housing is provided with a plurality of second spray holes on the side away from the liquid ammonia high-pressure injector.

[0013] In some embodiments of the present invention, the liquid ammonia high-pressure injector includes a nozzle, the nozzle having a plurality of injection holes arranged in a spiral pattern around the central axis of the nozzle.

[0014] In some embodiments of the present invention, the engine combustion system includes two jet ignition devices and one liquid ammonia high-pressure injector, with the two jet ignition devices located on both sides of the liquid ammonia high-pressure injector.

[0015] In a second aspect of the invention, a method for controlling an engine combustion system is provided, the method comprising the engine combustion system described in the above embodiments, the method comprising: When the piston of the engine moves downward, outside air enters the main combustion chamber through the intake manifold and gaseous ammonia is injected into the intake manifold through the low-pressure ammonia injector, forming a low-pressure ammonia-air mixture in the main combustion chamber; When the piston moves upward to 50° before the top dead center, liquid ammonia is injected into the main combustion chamber through a high-pressure liquid ammonia injector and injected continuously for 15°. The liquid ammonia mixes with the low-pressure ammonia-air mixture to form an ammonia mixture. When the piston moves upward to between 25° and 10° before top dead center, the hydrogen injector injects hydrogen fuel into the ignition chamber to form a fuel-rich premixed gas. The spark plug ignites the fuel-rich premixed gas to form a jet flame. The jet flame enters the main combustion chamber through the first nozzle and the second nozzle and ignites the ammonia mixture. After ignition, the main combustion chamber enters the combustion stage, and the high-temperature and high-pressure gas generated pushes the piston downward, which outputs power through the crankshaft of the engine. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of the structure of an engine combustion system according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of the structure of the first and second nozzles according to an embodiment of the present invention is shown. Figure 3 yes Figure 1 Schematic diagram of the cross section at point AA; Figure 4 A partial structural diagram of an engine combustion system according to an embodiment of the present invention is shown schematically. Figure 5 A partial structural diagram of another engine combustion system according to an embodiment of the present invention is shown schematically; Figure 6 A partial structural schematic diagram of another engine combustion system according to an embodiment of the present invention is shown.

[0017] The labels in the attached diagram are as follows: 10. Cylinder; 11. Main combustion chamber; 12. Piston; 13. Crankshaft crank; 14. Exhaust port; 15. Exhaust gas treatment system; 100. Jet ignition device; 110. Housing; 120. Ignition chamber; 130. Nozzle; 131. First nozzle; 132. Second nozzle; 140. Hydrogen injector; 150. Spark plug; 200. Air intake; 300. Low-pressure ammonia injector; 400. High-pressure liquid ammonia injector; 410. Injection orifice; 500, pressure regulator; 600, liquid ammonia storage tank. Detailed Implementation

[0018] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0019] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0020] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0021] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations.

[0022] In existing research on ammonia-fueled engines, a relatively mature technical solution involves introducing a jet ignition structure to improve the ignition and combustion process of ammonia fuel through a separate combustion organization of the ignition chamber and the main combustion chamber. This solution typically involves an integrated or separate ignition chamber structure at the top of the main combustion chamber. Inside the ignition chamber, a spark plug and fuel injection device are installed. During the later stages of the compression stroke, a certain proportion of fuel is injected into the ignition chamber to form a rich mixture, which is then ignited and burned by the spark plug, rapidly generating a high-temperature, high-pressure flame cloud within the ignition chamber. Several nozzles are machined on the outer wall of the ignition chamber, spatially arranged in a regular or approximately symmetrical pattern. Their axial tilt angle and radial pointing angle are structurally designed to match the spatial shape of the main combustion chamber, the compression end profile, and the fuel distribution area. This allows the high-temperature, high-pressure flame generated in the ignition chamber to be injected into the main combustion chamber as a jet through the nozzles, forming several jet flames with a certain penetration capability and diffusion angle within the cylinder. This results in multiple spatially dispersed flame cores within the main combustion chamber, improving the ignition coverage area in the initial stages of combustion.

[0023] In terms of nozzle structure design, this type of technology typically employs nozzle structures of uniform specifications or similar diameters. The number of nozzles is determined based on the cylinder bore diameter and compression end structure. The nozzle diameter, injection angle, and ignition chamber volume parameters are comprehensively matched through experiments or simulations to adjust the momentum flux, injection velocity, and flame volume characteristics of the jet flame. During operation, the engine first completes the fuel-rich mixing, ignition, and pressure rise process in the ignition chamber during the later stages of the compression stroke. Subsequently, the jet flame is injected at high speed from the nozzle into the main combustion chamber, igniting the ammonia fuel mixture in the cylinder and forming a continuous combustion zone along the jet path. Simultaneously, the jet entrainment and shearing effects enhance local mixing.

[0024] Existing technologies using nozzle structures of uniform specifications or similar diameters suffer from the following drawbacks: Under conditions requiring high ignition energy, such as cold starts, lean combustion, or high exhaust gas recirculation rates, while a single small-diameter nozzle can generate a high-speed jet to ensure ignition reliability, its limited flow area leads to poor gas exchange between the ignition chamber and the main combustion chamber, resulting in a small jet coverage area and difficulty meeting the demands of high-flow-rate, widely distributed flame propagation for rapid combustion under medium-to-high loads. Conversely, while a single large-diameter nozzle can achieve a high-flow-rate jet, insufficient jet flow and weak penetration under difficult ignition conditions can easily lead to ignition instability or combustion lag. Furthermore, uniform nozzle specifications cannot dynamically match injection characteristics to changes in ignition chamber pressure, easily resulting in incomplete scavenging and a high residual exhaust gas coefficient, thus affecting cycle stability. Moreover, it has poor adaptability to different fuels and a wide range of operating conditions, making it difficult to simultaneously achieve both ignition reliability and combustion rate across the entire operating range. The engine combustion system provided by this technical solution effectively solves the above problems.

[0025] Figure 1 A schematic diagram of the structure of an engine combustion system according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of the structure of the first nozzle 131 and the second nozzle 132 according to an embodiment of the present invention is shown. Figure 3 yes Figure 1 A schematic diagram of the cross-section at point AA. (See diagram below.) Figure 1 , Figure 2 and Figure 3As shown, the present invention proposes an engine combustion system, including a cylinder 10 and a jet ignition device 100. The cylinder 10 includes a main combustion chamber 11; the jet ignition device 100 includes a housing 110, which is provided with an ignition chamber 120 and a nozzle 130. The ignition chamber 120 is connected to the main combustion chamber 11 of the cylinder through the nozzle 130. The nozzle 130 includes a first nozzle 131 and a second nozzle 132, and the first nozzle 131 and the second nozzle 132 are respectively connected to the ignition chamber 120 and the main combustion chamber 11. Chamber 11; along the direction from the inlet (a1 in the figure) to the outlet (a2 in the figure) of the first nozzle 131, the inner diameter of the first nozzle 131 gradually decreases; along the direction from the inlet (b1 in the figure) to the outlet (b2 in the figure) of the second nozzle 132, the inner diameter of the second nozzle 132 gradually increases; the inlet inner diameter of the first nozzle 131 at the inlet of the first nozzle 131 is smaller than the inlet inner diameter of the second nozzle 132 at the inlet of the second nozzle 132.

[0026] In traditional structural designs, the nozzle 130 has a single aperture, making it difficult to simultaneously meet the demands for high-speed, concentrated jets in the initial ignition stage and for large-area, high-flow-rate jets in the later stages of flame development. The engine combustion system in this technical solution employs a gradient design for the nozzle 130 size in the ignition chamber 120. The small-diameter first nozzle 131 uses a tapering structure, generating a high-speed, high-momentum flame jet through throat acceleration, effectively improving jet penetration, significantly expanding the effective ignition area, and increasing in-cylinder turbulence intensity. The large-diameter second nozzle 132 uses a expanding structure, allowing the flame jet to achieve stable expansion and energy release after exiting the nozzle, thereby enhancing overall ignition energy and reducing the risk of flame quenching. Therefore, by combining nozzles 130 with different apertures, the first nozzle 131 is responsible for ignition reliability, while the second nozzle 132 is responsible for combustion speed and safety. These two types complement each other, providing wider fuel adaptability without altering the combustion system hardware.

[0027] Optionally, the inlet inner diameter of the first nozzle 131 can be 1.5 mm, and the inlet inner diameter of the second nozzle 132 can be 2.5 mm. Choosing the combination of 1.5 mm and 2.5 mm nozzle diameters allows for a clear functional division and dynamic matching of the flow area ratio: on the one hand, the 1.5 mm small nozzle generates a high-speed jet in the initial stage of ignition, ensuring ignition reliability under high ignition energy requirements such as cold start and lean combustion; on the other hand, the 2.5 mm large nozzle provides sufficient flow capacity in the middle and later stages of combustion, meeting the needs of high flow rate and wide-range flame propagation under medium to high loads. This nozzle diameter ratio avoids functional overlap and loss of complementary advantages due to excessively small differences, while also preventing excessive differences from causing blockage of the small nozzle or excessive pressure relief and insufficient pressure build-up in the ignition chamber due to excessively large differences, thus achieving the optimal balance between ignition reliability and combustion rate across the entire operating range.

[0028] Furthermore, the angle between the injection direction of the first nozzle 131 and the axis of the ignition chamber 120 ( Figure 2 The angle α is 25° to 35°.

[0029] The first nozzle 131 is used to generate a high-speed, concentrated, and highly penetrating jet, mainly acting on the far-field mixing zone, which is beneficial for quickly igniting the air-fuel mixture in the main combustion chamber 11 that is far from the ignition chamber 120. Simultaneously, it enables the jet to form a certain vortex or tumble within the combustion chamber, promoting flame propagation speed and combustion uniformity. Understandably, setting the included angle to 25°–35° is an optimization result that comprehensively considers jet penetration, flame propagation range, and structural layout feasibility. If the angle is too small (e.g., close to 0°), the jet from the first nozzle 131 will be ejected along a direction close to the axis of the ignition chamber 120. Although the penetration distance is relatively long, the jet is too concentrated, making it difficult to utilize the flow field within the main combustion chamber 11 to form a wide-area flame propagation. If the angle is too large (e.g., exceeding 45°), the jet direction is too oblique. On the one hand, too much jet momentum is consumed in the radial component, resulting in insufficient axial penetration depth, making it difficult to propagate the flame to the far end of the main combustion chamber 11 under lean-burn or high EGR conditions. An angle of 25° to 35° ensures sufficient axial penetration depth while guiding the flame towards the central region of the main combustion chamber 11 using the radial component. This allows the flame to form a combined jet spatial layout with the second nozzle 132, achieving synergistic optimization of ignition reliability and combustion speed. For example, the angle between the injection direction of the first nozzle 131 and the axis of the ignition chamber 120 can be 25°, 30°, or 35°, etc.

[0030] Furthermore, the angle between the injection direction of the second nozzle 132 and the axis of the ignition chamber 120 ( Figure 2 The β value is 55° to 65°.

[0031] The second nozzle 132 has a large diffusion angle and a wide coverage area, mainly covering the near-field mixing zone. This prevents ignition energy from being too concentrated, allowing for rapid ignition of the near-field area and promoting overall combustion, achieving the dual functions of ignition and rapid combustion. The combined effect of the first nozzle 131 and the second nozzle 132 can create a more uniform temperature field and flame distribution within the combustion chamber, avoiding localized overheating or unignited areas. Their different directions allow the jets to be spatially staggered, reducing mutual interference and fully utilizing the jet energy generated within the ignition chamber 120. Setting the angle to 55°–65° is the optimal choice for balancing the coverage and penetration depth of the large nozzle jet and avoiding jet interference. If the angle is too small (e.g., close to 30° or less), the direction of the large nozzle jet is too close to the ignition chamber axis. Although the axial penetration distance increases, the radial diffusion is insufficient, making it difficult to achieve rapid flame propagation over a wide range in the main combustion chamber under medium to high loads. It is also easy to overlap with the direction of the small nozzle jet, resulting in concentrated rather than complementary jet energy. If the angle is too large (e.g., exceeding 75° or even close to 90°), the jet is almost perpendicular to the ignition chamber axis. Although the radial coverage is wide, the axial penetration depth decreases significantly, making it impossible to effectively deliver the flame to the far end of the combustion chamber. At the same time, an excessively large deflection angle may cause the jet to directly impact the cylinder wall or piston top edge, increasing heat loss and inducing local overheating or knocking tendencies. The 55°–65° angle, based on the high flow rate characteristics of the large nozzle, achieves a balance between wide radial coverage and sufficient axial penetration. It also forms an approximately 30° angle difference with the 30° small nozzle, allowing the two jets to be spatially staggered. This avoids interference and creates a three-dimensional flame propagation network within the combustion chamber, comprehensively improving combustion efficiency and stability under medium to high loads. For example, the angle between the injection direction of the second nozzle 132 and the axis of the ignition chamber 120 can be 55°, 60°, or 65°, etc.

[0032] Furthermore, the engine combustion system also includes an intake duct 200, a low-pressure ammonia injector 300, and a liquid ammonia high-pressure injector 400. One end of the intake duct 200 is connected to an external air source, and the other end of the intake duct 200 is connected to the main combustion chamber 11. The low-pressure ammonia injector 300 is installed on the intake duct 200 and is used to inject gaseous ammonia into the intake duct 200. The liquid ammonia high-pressure injector 400 is used to inject liquid ammonia into the main combustion chamber 11.

[0033] The intake duct 200 serves as the channel for air to enter the main combustion chamber 11. One end connects to an external air source, and the other end connects to the main combustion chamber 11. It is responsible for supplying fresh air into the cylinder and providing space and flow field conditions for its mixing with fuel. The low-pressure ammonia injector 300 pre-mixes gaseous ammonia with air within the intake duct 200 to form a relatively uniform lean mixture that enters the main combustion chamber 11. This is suitable for low-load or homogeneous combustion conditions. By using a longer mixing time, it improves the atomization and evaporation of ammonia fuel and the uniformity of mixing, while reducing dependence on the high-pressure injection system. The liquid ammonia high-pressure injector 400 injects liquid ammonia directly into the cylinder under high pressure and with precision during the later stages of the compression stroke or the early stages of the power stroke. It utilizes the endothermic properties of liquid ammonia to reduce the cylinder temperature and suppress knocking. Through high-pressure atomization, it forms a localized rich zone, meeting the requirements for ignition energy and combustion speed under high-load conditions, and achieving direct injection and stratified combustion control of ammonia fuel in the cylinder.

[0034] The engine combustion system operates as follows: During the intake stroke, the low-pressure ammonia injector 300 injects gaseous ammonia into the intake manifold 200, where it mixes with external air to form a premixed gas before entering the main combustion chamber 11. During the later stages of the compression stroke or the initial stage of the power stroke, the high-pressure liquid ammonia injector 400 directly injects liquid ammonia into the main combustion chamber 11. The vaporization of the liquid ammonia absorbs heat, reducing the local temperature of the main combustion chamber 11 and effectively suppressing knocking. At this time, the jet ignition device 100 is activated. After the mixture in the ignition chamber 120 is ignited, a high-temperature, high-pressure flame jet is injected into the main combustion chamber 11 through the first nozzle 131 and the second nozzle 132, respectively, with concentrated penetration and wide-angle diffusion. The jet from the first nozzle 131 ignites the lean mixture at the far end, while the jet from the second nozzle 132 rapidly ignites the near-field region. Together, they achieve a dual mode of premixed gas and diffusion combustion, ensuring stable, efficient, and low-emission combustion of ammonia fuel under a wide range of operating conditions.

[0035] Further, see Figure 3 and Figure 4 The housing 110 has a plurality of first nozzles 131 and a plurality of second nozzles 132 on the side facing the liquid ammonia high-pressure injector 400, and the housing 110 has a plurality of second nozzles 132 on the side away from the liquid ammonia high-pressure injector 400.

[0036] The nozzle 130, with this layout, can form a significant asymmetric jet distribution, enabling the side with higher fuel concentration to generate more high-energy flame jets and flame cores, further enhancing ignition energy and improving overall ignition reliability and combustion stability to meet the requirements of rapid ignition and short combustion duration under high-speed combustion cycles. This layout can be applied to small-bore engines (bore less than or equal to 300mm). Optionally, there is one jet ignition device 100 and one liquid ammonia high-pressure injector 400. In this embodiment, the housing 110 has two first nozzles 131 and two second nozzles 132 on the side facing the liquid ammonia high-pressure injector 400, and two second nozzles 132 on the side away from the liquid ammonia high-pressure injector 400. In other embodiments, the number of first nozzles 131 and second nozzles 132 can be set according to usage requirements.

[0037] For example, see Figure 5 In small- and medium-bore engines, the engine combustion system may also include two jet ignition devices 100 and a liquid ammonia high-pressure injector 400, with the two jet ignition devices 100 located on either side of the liquid ammonia high-pressure injector 400. The dual ignition chamber 120 structure, with different ignition times, achieves a more comprehensive flame jet range, thereby enhancing the combustion of ammonia fuel.

[0038] See Figure 6 In some embodiments, multiple liquid ammonia high-pressure injectors 400 are provided, and the multiple liquid ammonia high-pressure injectors 400 are equally spaced along the circumferential distance of the jet ignition device 100.

[0039] This layout can be applied to large-bore engines (bore greater than 300mm). Figure 6In the illustrated embodiment, there are three liquid ammonia high-pressure injectors 400, which are circumferentially spaced equally between the three liquid ammonia high-pressure injectors 400 and the jet ignition device 100. Understandably, if the number of liquid ammonia high-pressure injectors 400 is too small, it can easily lead to uneven distribution of ammonia fuel in the main combustion chamber 11, forming locally rich or lean areas. This makes it difficult to effectively coordinate with the multi-point flame generated by the jet ignition device 100, especially under high-load conditions, which can easily result in incomplete combustion, worsened emissions, or excessively high local heat loads. If the number is too large, although theoretically it can improve fuel distribution uniformity, it will significantly increase system complexity and manufacturing costs. At the same time, the control precision requirements for each injector are higher, and the risk of spray interference between injectors increases, potentially causing spray overlap or collision, which in turn affects atomization quality and the consistency of mixture formation. The scheme of arranging three liquid ammonia high-pressure injectors 400 at 120° intervals can not only form a symmetrical and uniform fuel distribution around the jet ignition device, allowing the injected liquid ammonia to fully contact the multiple flames generated by the jet ignition device, but also avoid the cost and control burden caused by excessive redundancy, thus achieving the optimal spatial matching of fuel supply and ignition energy.

[0040] Further, see Figure 5 The liquid ammonia high-pressure injector 400 includes a nozzle with multiple injection holes 410 arranged in a spiral pattern around the central axis of the nozzle. That is, the radial direction of the injection holes 410 (perpendicular to the injection direction) forms an angle with the radial direction of the nozzle.

[0041] This allows the liquid ammonia jet injected into the cylinder to simultaneously acquire velocity components in both the radial and circumferential directions, thereby inducing a three-dimensional vortex field with helical characteristics inside the cylinder 10. This vortex field, on the one hand, significantly promotes the atomization, evaporation, and rapid, uniform mixing of liquid ammonia with air by enhancing the turbulence intensity within the cylinder, effectively avoiding the formation of localized over-rich zones; on the other hand, the helical flow field guides the flame front to accelerate its propagation along the vortex direction during combustion, shortening the combustion duration and improving combustion rate and thermal efficiency. Furthermore, this three-dimensional vortex field, in conjunction with the multiple ignition jets generated by the jet ignition device, achieves spatial synergy, optimizing fuel distribution, mixture formation, and flame propagation within the cylinder, significantly improving combustion stability and adaptability to different operating conditions.

[0042] See Figure 6 Multiple nozzles 130 are arranged in a spiral pattern around the central axis of the ignition chamber 120. That is, the radial direction of the nozzles 130 (perpendicular to the injection direction) is set at an angle to the radial direction of the ignition chamber 120.

[0043] The jets, with each nozzle 130 arranged spirally around the central axis of the ignition chamber 120, generate velocity components in both the radial and circumferential directions, thereby inducing a strong vortex field with three-dimensional spiral characteristics within the main combustion chamber 11. This vortex field significantly improves the mixing uniformity of ammonia fuel and air by enhancing turbulent disturbance, effectively suppressing the formation of locally rich or lean regions. Furthermore, the spiral flow field rapidly stretches and propagates the flame front along the vortex direction, significantly shortening the combustion duration and improving combustion rate and thermal efficiency. Simultaneously, the uniformly distributed multiple spiral jets and the circumferentially equidistant liquid ammonia high-pressure injectors 400 form a spatial synergy, optimizing fuel supply, mixture formation, and flame propagation in three-dimensional space, significantly improving combustion stability, cycle consistency, and adaptability to a wide range of operating conditions.

[0044] Furthermore, the engine combustion system also includes an exhaust gas processor 15, with cylinder 10 connected to the exhaust gas processor 15 via exhaust manifold 14. The exhaust gas processor 15 converts carbon monoxide, carbon oxides, and harmful particles into harmless substances to meet regulatory requirements; it provides an air-fuel ratio signal to the control unit via an oxygen sensor to optimize the control strategy of the jet ignition system; it works in conjunction with the combustion system to balance cold start ignition and high-load protection; and it achieves overall optimization of efficient combustion and low emissions.

[0045] Furthermore, the engine combustion system also includes a pressure reducer 500 and a liquid ammonia storage tank 600. A high-pressure liquid ammonia injector 400 is connected to the liquid ammonia storage tank 600, and a low-pressure ammonia injector 300 is connected to the liquid ammonia storage tank 600 via the pressure reducer 500. Understandably, the liquid ammonia storage tank 600 is used to store liquid ammonia, and the pressure reducer 500 is used to convert liquid ammonia into gaseous ammonia.

[0046] Furthermore, this technical solution also provides a control method for an engine combustion system, implemented based on the aforementioned engine combustion system. The control method for the engine combustion system includes: When the piston 12 of the engine moves downward, outside air enters the main combustion chamber 11 through the intake duct 200 and gaseous ammonia is injected into the intake duct 200 through the low-pressure ammonia injector 300, forming a low-pressure ammonia-air mixture in the main combustion chamber 11. When the piston 12 moves upward to 50° before the top dead center, liquid ammonia is injected into the main combustion chamber 11 through the liquid ammonia high-pressure injector 400, and the injection continues for 15°. The liquid ammonia mixes with the low-pressure ammonia-air mixture to form an ammonia mixture. When the piston 12 moves upward to between 25° and 10° before top dead center, the hydrogen injector 140 injects hydrogen fuel into the ignition chamber 120 to form a rich premixed gas. The spark plug 150 ignites the rich premixed gas to form a jet flame. The jet flame enters the main combustion chamber 11 through the first nozzle 131 and the second nozzle 132 and ignites the ammonia mixture. After ignition, the main combustion chamber 11 enters the combustion stage, and the high-temperature and high-pressure gas generated pushes the piston 12 downward, which outputs power through the crankshaft handle 13 of the engine.

[0047] Specifically, the engine ignition process includes the intake stage, the liquid ammonia injection stage, the 120° jet ignition stage in the ignition chamber, and the expansion power and intake stage.

[0048] Intake stage: Piston 12 moves downward, and outside air enters the cylinder through intake port 200. A small amount of gaseous ammonia is injected through pressure reducer 500 and low-pressure ammonia injector 300 to improve initial combustibility and improve the problem of difficult low-temperature ignition of ammonia fuel.

[0049] Liquid ammonia injection stage: Piston 12 moves upward into the compression stroke. 50° before top dead center, liquid ammonia enters the cylinder through the high-pressure liquid ammonia injector 400 and nozzle 130, mixing with the previously low-pressure ammonia-air mixture. In low-speed, large-bore engines, three high-pressure liquid ammonia injectors simultaneously inject, creating a circumferential turbulent flow field within the cylinder; in medium and small-bore engines, central injection creates a uniform mixing field, continuously injecting for 15°.

[0050] Ignition chamber 120 jet ignition stage: At the end of the compression stroke, ignition occurs in ignition chamber 120, forming a high-energy jet flame. For large-bore engines, between 25° and 10° before top dead center, hydrogen fuel is injected by hydrogen injector 140 to form a rich premixed gas; spark plug 150 ignites to form a jet flame; the jet flame enters the main combustion chamber 11 through the gradient aperture nozzle 130 (a first nozzle 131 that gradually narrows and a second nozzle 132 that gradually widens), igniting the ammonia mixture in the main combustion chamber 11. For small- and medium-bore engines, between 25° and 10° before top dead center, hydrogen fuel is injected by hydrogen injector 140 to form a rich premixed gas; spark plug 150 ignites to form a jet flame; the jet flame forms four jets to ignite a high-concentration ammonia mixture area on the side near the liquid ammonia high-pressure injector 400 through gradient aperture nozzles 130 (a first nozzle 131 that tapers and a second nozzle 132 that expands), and two jets to ignite a low-concentration ammonia mixture area on the side away from the liquid ammonia high-pressure injector 400. If a small- or medium-bore engine has a two-ignition-chamber 120 structure, the ignition chamber 120 in the area between the intake manifold 200 and the liquid ammonia high-pressure injector 400 is between 25° and 10° before top dead center, where hydrogen fuel is injected by the hydrogen injector 140 to form a rich premixed gas; the spark plug 150 ignites it to form a jet flame; the ignition chamber 120 on the other side is between 5° and -5° before top dead center, where hydrogen fuel is injected and ignited by the spark plug 150 to form a jet flame to enhance the ignition and combustion of the high-concentration ammonia fuel area.

[0051] Expansion and Exhaust: After jet ignition, the ammonia fuel in the main combustion chamber 11 enters the combustion stage. The high-temperature and high-pressure gas generated pushes the piston 12 downward, and outputs power through the crankshaft handle 13. The combustion products are discharged through the exhaust duct 14, the exhaust gas processor 15 (used to purify NH3, NOx and other emissions), and the exhaust pipe, achieving clean emissions.

[0052] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An engine combustion system, characterized in that, include: Cylinder (10), the cylinder (10) includes a main combustion chamber (11); A jet ignition device (100) includes a housing (110), which is provided with an ignition chamber (120) and a nozzle (130). The nozzle (130) includes a first nozzle (131) and a second nozzle (132), and the first nozzle (131) and the second nozzle (132) are respectively connected to the ignition chamber (120) and the main combustion chamber (11). Along the direction from the inlet of the first nozzle (131) to the outlet of the first nozzle (131), the inner diameter of the first nozzle (131) gradually decreases; Along the direction from the inlet to the outlet of the second nozzle (132), the inner diameter of the second nozzle (132) gradually increases; The inner diameter of the inlet of the first nozzle (131) at the entrance of the first nozzle (131) is smaller than the inner diameter of the inlet of the second nozzle (132) at the entrance of the second nozzle (132).

2. The engine combustion system according to claim 1, characterized in that, The angle between the injection direction of the first nozzle (131) and the axis of the ignition chamber (120) is 25° to 35°.

3. The engine combustion system according to claim 1, characterized in that, The angle between the injection direction of the second nozzle (132) and the axis of the ignition chamber (120) is 55° to 65°.

4. The engine combustion system according to claim 1, characterized in that, The plurality of nozzles (130) are arranged in a spiral around the central axis of the ignition chamber (120).

5. The engine combustion system according to claim 1, characterized in that, The engine combustion system also includes an air intake (200), a low-pressure ammonia injector (300), and a liquid ammonia high-pressure injector (400). One end of the air intake (200) is connected to an external air source, and the other end of the air intake (200) is connected to the main combustion chamber (11). The low-pressure ammonia injector (300) is installed on the air intake (200) and is used to inject gaseous ammonia into the air intake (200). The liquid ammonia high-pressure injector (400) is used to inject liquid ammonia into the main combustion chamber (11).

6. The engine combustion system according to claim 5, characterized in that, Multiple liquid ammonia high-pressure injectors (400) are provided, and the multiple liquid ammonia high-pressure injectors (400) are equally spaced along the circumferential interval of the jet ignition device (100).

7. The engine combustion system according to claim 5, characterized in that, The housing (110) has a plurality of first nozzles (131) and a plurality of second nozzles (132) on the side facing the liquid ammonia high-pressure injector (400), and the housing (110) has a plurality of second nozzles (132) on the side away from the liquid ammonia high-pressure injector (400).

8. The engine combustion system according to claim 5, characterized in that, The liquid ammonia high-pressure injector (400) includes a nozzle, on which a plurality of injection holes (410) are provided, and the plurality of injection holes (410) are arranged in a spiral around the central axis of the nozzle.

9. The engine combustion system according to claim 5, characterized in that, The engine combustion system includes two jet ignition devices (100) and one liquid ammonia high-pressure injector (400), with the two jet ignition devices (100) located on both sides of the liquid ammonia high-pressure injector (400).

10. A control method for an engine combustion system, characterized in that, The control method of the engine combustion system, implemented based on any one of claims 1-9, includes: When the piston (12) of the engine moves downward, outside air enters the main combustion chamber (11) through the intake manifold (200) and gaseous ammonia is injected into the intake manifold (200) through the low-pressure ammonia injector (300) to form a low-pressure ammonia-air mixture in the main combustion chamber (11); When the piston (12) moves upward to 50° before the top dead center, liquid ammonia is injected into the main combustion chamber (11) through the liquid ammonia high-pressure injector (400) and injected continuously for 15°. The liquid ammonia mixes with the low-pressure ammonia-air mixture to form an ammonia mixture. When the piston (12) moves upward to between 25° and 10° before the top dead center, the hydrogen injector (140) injects hydrogen fuel into the ignition chamber (120) to form a fuel-rich premixed gas. The spark plug (150) ignites the fuel-rich premixed gas to form a jet flame. The jet flame enters the main combustion chamber (11) through the first nozzle (131) and the second nozzle (132) and ignites the ammonia mixture. After ignition, the main combustion chamber (11) enters the combustion stage, and the generated high-temperature and high-pressure gas pushes the piston (12) downward, and outputs power through the crankshaft handle (13) of the engine.

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