Injection structure for a diesel-ammonia engine

Abstract

The utility model relates to the technical field of engine, and disclose a kind of diesel ammonia engine injection structure, including engine combustion chamber, intake port and exhaust passage being set on its cylinder cover, and double direct injection oil injection assembly being installed on the upper end of the cylinder cover, the lower end injection port of the double direct injection oil injection assembly extends to the engine combustion chamber, and the double direct injection oil injection assembly includes liquid ammonia oil atomizer and diesel oil atomizer;The liquid ammonia oil atomizer is centrally arranged and coincides with the axis of the engine combustion chamber.The utility model is centrally arranged by liquid ammonia oil atomizer, and diesel oil atomizer is arranged in its side with specific small offset amount in parallel, creates the best oil beam space distribution, and this arrangement makes diesel oil beam can efficiently, in time ignite its periphery liquid ammonia oil beam, significantly improves the ignition ratio and combustion isovolumic degree of liquid ammonia, shortens combustion duration, so that excellent thermal efficiency can be obtained under high load and low load.

Description

Technical Field

[0001] This utility model relates to the field of engine technology, specifically to a diesel-ammonia engine injection structure. Background Technology

[0002] Reducing engine carbon emissions to achieve the national "dual carbon" goal is an important direction for the development of engine technology. Compression ignition engines urgently need new clean alternative fuels. In the past, there has been more research on low-carbon fuels such as natural gas and methanol, while carbon-free fuels such as hydrogen and ammonia are gradually becoming research hotspots.

[0003] Compared with hydrogen, ammonia has significant advantages: the production process is mature and the cost is low; it can be liquefied and stored at room temperature and a pressure of about 1.0 MPa; storage and transportation are safe and convenient; and it is not prone to explosion. At the same time, ammonia has a high energy density, with the energy density of liquefied ammonia being about 1.6 times that of liquefied hydrogen, making it a good carrier for hydrogen.

[0004] However, the low flame velocity, high auto-ignition temperature, high ignition energy requirement, and narrow combustion limit of ammonia fuel restrict its application in compression ignition engines.

[0005] Currently, there are two main combustion modes for ammonia fuel in engines: low-pressure injection dual-fuel and high-pressure injection dual-fuel. Low-pressure mode (such as intake manifold injection of ammonia or in-cylinder low-pressure direct injection of ammonia) has problems such as incomplete combustion, power reduction, and low thermal efficiency. High-pressure mode achieves non-premixed combustion of ammonia by in-cylinder high-pressure direct injection of diesel and liquid ammonia. Its heat release rate is mainly affected by the spray mixing rate, which greatly improves the controllability and robustness of combustion and can effectively avoid the problems of low-pressure combustion.

[0006] However, in existing high-pressure direct injection dual-fuel systems, the injection strategy and spatial arrangement of diesel and liquid ammonia have a decisive impact on ignition efficiency, combustion efficiency, and final thermal efficiency. If the arrangement is improper, it can lead to problems such as mutual interference of fuel jets, incomplete ignition, long combustion duration, and low thermal efficiency.

[0007] Therefore, there is an urgent need for an optimized injection structure arrangement to solve the problems of low ignition efficiency and low combustion efficiency of liquid ammonia in compression ignition engines. Utility Model Content

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a diesel-ammonia engine injection structure. By optimizing the relative spatial position of the diesel injector and the liquid ammonia injector, the problem of low ignition efficiency and low combustion efficiency of liquid ammonia is solved, thereby achieving efficient and stable diesel ignition and high-pressure direct injection of liquid ammonia combustion.

[0009] This utility model proposes a diesel-ammonia engine injection structure, including an engine combustion chamber, an intake manifold and an exhaust manifold disposed on its cylinder head, and a dual direct injection fuel injection assembly mounted on the upper end of the cylinder head. The lower injection port of the dual direct injection fuel injection assembly extends into the engine combustion chamber. The dual direct injection fuel injection assembly includes a liquid ammonia injector and a diesel injector. The liquid ammonia injector is centrally located and coincides with the axis of the engine combustion chamber. The diesel injector is arranged parallel to the side of the liquid ammonia injector, and there is a horizontal offset L between the horizontal axis of the diesel injector and the horizontal axis of the liquid ammonia injector. Addressing the challenges of "difficult liquid ammonia ignition and low combustion efficiency" in diesel-ammonia engines, this design achieves a breakthrough through a "central liquid ammonia + side-offset diesel" layout. The liquid ammonia injector is centered and aligned with the combustion chamber axis, ensuring that the liquid ammonia jet evenly fills the central area of ​​the combustion chamber. The diesel injector is positioned parallel to the side with a horizontal offset, ensuring that the diesel jet is close to the liquid ammonia jet but does not directly collide with it. Diesel, due to its low ignition point, first undergoes compression ignition to form a high-temperature ignition core, which can efficiently ignite the surrounding liquid ammonia mixture. This avoids ignition delays caused by excessive offset or jet interference caused by insufficient offset. This layout is suitable for high-pressure direct injection mode, and combustion is controlled by the spray mixing rate, solving the problem of incomplete combustion in low-pressure injection, improving thermal efficiency and combustion stability, and meeting the clean fuel engine requirements under the "dual carbon" target.

[0010] As a further optimization of this utility model, the liquid ammonia injector and the diesel injector are each equipped with a nozzle at one end inside the engine combustion chamber, and the nozzle has multiple spray holes evenly distributed in the circumferential direction. The nozzle has circumferentially distributed spray holes, which allow liquid ammonia and diesel to form a uniformly diffused oil jet after being sprayed out. This increases the contact area between the fuel and air, improves atomization and mixing efficiency, and the multiple spray holes are designed to fit the combustion chamber space. This ensures that the fuel evenly covers the combustion area, avoiding incomplete combustion due to excessively high local concentrations or misfire due to excessively low concentrations. The circumferential layout also allows the diesel ignition core to be evenly distributed around the liquid ammonia oil jet, enabling simultaneous ignition of multiple ignition cores, shortening the combustion duration, and further improving combustion efficiency. This design also meets the stringent requirements of high-pressure direct injection for spray quality.

[0011] Furthermore, the nozzles of the liquid ammonia injector and the diesel injector are installed in the same direction, and there is no angular difference between their nozzles; With nozzles installed in the same direction and without angular difference, the diffusion directions of liquid ammonia and diesel fuel jets are synchronized, avoiding misalignment of the fuel jets due to angular deviations. This allows the diesel fuel jet to be precisely positioned in the "critical edge zone" of the liquid ammonia fuel jet, ensuring effective contact between the ignition core and the liquid ammonia mixture. At the same time, the consistent direction ensures a stable fuel jet development path without cross-interference, ensuring atomization quality and mixing uniformity. It also avoids local combustion lag or overheating caused by angular deviations, adapting to combustion requirements under different load conditions and improving operational adaptability.

[0012] Furthermore, both the liquid ammonia injector and the diesel injector have ten circumferentially distributed nozzles, and at least one of the two nozzles on opposite sides is closed. By sealing the nozzles on opposite sides, the structure avoids direct collision between liquid ammonia and diesel fuel jets at close range, preventing atomization breakage and energy dissipation caused by mutual penetration of fuel jets, and ensuring the complete development of each fuel jet. At the same time, the non-opposite side nozzles are retained to ensure fuel coverage and not affect mixing efficiency. This design further optimizes the spatial distribution of fuel jets, avoids negative interference, and enables the diesel ignition core to ignite liquid ammonia more efficiently. It is suitable for precise combustion control under high-pressure direct injection, reducing incomplete combustion and emissions.

[0013] As a further optimization of this utility model, the horizontal offset L ranges from 8mm to 12mm. Within this range, the optimal balance between diesel ignition and fuel jet interference can be found. If the offset is too small, the fuel jet will interfere prematurely, affecting atomization. If it is too large, the diesel ignition core will be too far from some of the liquid ammonia, resulting in untimely ignition. This range is suitable for different combustion chamber sizes and injection pressures, ensuring efficient ignition of liquid ammonia by diesel under both high and low loads, improving thermal efficiency and combustion stability, and avoiding prolonged combustion duration or decreased thermal efficiency due to improper offset.

[0014] Furthermore, the horizontal offset L is 10mm, which is the optimal value for the offset. Experiments have verified that the spatial position of the diesel fuel jet and the liquid ammonia fuel jet is most reasonable at this value. The diesel ignition core can cover the liquid ammonia fuel jet to the maximum extent, resulting in the highest ignition efficiency, the best combustion isochoricity, and excellent thermal efficiency across the entire load range. At the same time, this offset can be adapted to the combustion chamber structure of most diesel-ammonia engines without requiring significant modifications to the cylinder head. It has strong engineering practicality and is convenient for upgrading and adapting existing engines.

[0015] As a further optimization of this utility model, there is a height difference between the nozzles at the lower ends of the liquid ammonia injector and the diesel injector, so that the oil jets sprayed by the two injectors are at different horizontal heights. The nozzle height difference causes the fuel jet to be distributed in layers in the vertical direction, which further avoids mutual interference between fuel jets in space. Even if it is offset in the horizontal direction, fuel jets at different heights will not cross-penetrate, ensuring that their atomization and mixing processes are independent. The layered layout can also adapt to the vertical space of the combustion chamber, so that the fuel fills the combustion chamber more evenly, avoids local uneven concentration, and further improves combustion stability and efficiency, which is in line with the high requirements of high-pressure direct injection for the independence of the spray space.

[0016] The diesel-ammonia engine injection structure proposed in this utility model has the following beneficial effects: (i) By centering the liquid ammonia injector and arranging the diesel injector parallel to its side with a specific small offset, the optimal fuel jet spatial distribution is created. This arrangement enables the diesel fuel jet to efficiently and promptly ignite the surrounding liquid ammonia fuel jet, significantly improving the ignition ratio and combustion isochoricity of liquid ammonia, and shortening the combustion duration, thus achieving excellent thermal efficiency under both high and low loads. (ii) By setting the nozzles with no angle difference and sealing at least one nozzle on the opposite side, the direct collision between diesel and liquid ammonia jets at close range is effectively prevented, thus avoiding mutual interference and energy dissipation and ensuring the complete development and full mixing of their respective jets. (iii) The high-pressure direct injection strategy is adopted, and the combustion process is mainly controlled by the spray mixing rate rather than the premixing process. This makes the combustion process more controllable and more adaptable to changes in operating conditions, effectively avoiding problems such as misfire and knocking in the low-pressure premixed combustion mode. (iv) This structure is based on mature in-cylinder direct injection technology, requires minimal modification to existing engines, and mainly improves performance by optimizing the relative positions of the two injectors. It has high engineering practicality and promotion value.

[0017] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a top view of the structure of this utility model; Figure 3 This is a three-dimensional structural diagram of the dual direct injection fuel injection assembly of this utility model; Figure 4 This is a top view of the dual direct injection fuel injection assembly of this utility model; Figure 5 This is a bottom view of the dual direct injection fuel injection assembly of this utility model; Figure 6 This is a three-dimensional structural diagram of the dual direct injection fuel injection assembly in another embodiment of the present invention.

[0019] Attached diagrams: 1. Engine combustion chamber; 2. Intake manifold; 3. Exhaust manifold; 4. Liquid ammonia injector; 5. Diesel injector; 6. Nozzle; 7. Fuel jet. Detailed Implementation

[0020] The embodiments of this utility model are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0021] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0022] like Figure 1 and Figure 2 As shown, the diesel-ammonia engine injection structure of this utility model mainly includes an engine combustion chamber 1, an intake manifold 2, an exhaust manifold 3, and a dual direct injection fuel injection assembly. The dual direct injection fuel injection assembly is installed on the upper end of the cylinder head of the engine combustion chamber 1, and its lower end injection port extends into the combustion chamber.

[0023] like Figures 3 to 5 As shown, the core of the dual direct injection fuel injection assembly is that it includes a liquid ammonia injector 4 and a diesel injector 5. The liquid ammonia injector 4 is positioned in the center and coincides with the axis of the engine combustion chamber 1. The diesel injector 5 is installed parallel to the liquid ammonia injector 4, but its horizontal axis is offset by a horizontal amount L from the axis of the liquid ammonia injector 4. Extensive experimental verification has shown that the ideal range for the offset L is 8mm-12mm. When L=10mm, it exhibits excellent comprehensive performance under different loads.

[0024] Both injectors are equipped with nozzles 6 at their lower ends. Each nozzle 6 has multiple circumferentially distributed nozzle holes, such as ten. To ensure that the fuel jet 7 develops normally without interfering with each other, the two nozzles 6 are installed in the same direction, i.e., without any angular difference. Furthermore, on the side of the two nozzles 6 that are opposite to each other, at least one corresponding nozzle hole is sealed to prevent the diesel fuel jet from colliding head-on with the liquid ammonia fuel jet.

[0025] As another embodiment of this utility model, such as Figure 6As shown, the nozzles 6 at the lower ends of the liquid ammonia injector 4 and the diesel injector 5 can also have a certain height difference in the vertical direction. In this way, the oil jets 7 sprayed by the two injectors will be located on horizontal planes at different heights, which further avoids mutual interference between the oil jets in space.

[0026] The working principle of this invention is based on the combustion strategy of diesel igniting high-pressure direct injection of liquid ammonia. Its core lies in coordinating the injection, atomization, and mixing and ignition process of diesel and liquid ammonia through optimized spatial arrangement, as detailed below: When the engine is running, at the end of the compression stroke, the liquid ammonia injector 4 and the diesel injector 5, under the control of the electronic control unit, inject liquid ammonia and diesel into the engine combustion chamber 1 at high pressure and in a specific sequence according to the engine load requirements. Liquid ammonia and diesel fuel are sprayed out through multiple nozzles 6 to form an outwardly diffused fuel jet 7. Since the liquid ammonia injector 4 is centrally located, its fuel jet can evenly fill the central area of ​​the combustion chamber. The diesel fuel injector 5 is arranged parallel to the side with a small offset L, so that the diesel fuel jet is close to the liquid ammonia fuel jet but will not collide directly. This arrangement ensures that the diesel fuel jet is located in the critical "edge" area of ​​the liquid ammonia fuel jet. Due to its lower ignition point, diesel fuel first undergoes compression ignition in the high-temperature and high-pressure air, forming multiple high-temperature ignition nuclei. These ignition nuclei are located near the dense area of ​​the liquid ammonia fuel jet, enabling them to quickly and efficiently ignite the surrounding mixture of liquid ammonia vapor and air. By avoiding direct interference from the fuel jet, the liquid ammonia fuel jet can fully develop and mix with air, and be reliably ignited from the side by the diesel fuel ignition nuclei, thus achieving rapid and stable non-premixed combustion. The offset L is crucial. If L is too large, the diesel ignition core will be too far from some of the liquid ammonia, resulting in untimely and incomplete ignition, decreased combustion isochoricity, prolonged duration, and reduced thermal efficiency. If L is too small or there is no offset, the fuel jets may prematurely interpenetrate and interfere with each other, affecting atomization quality. The preferred L value of this invention is 8-12mm, which finds the optimal balance point, allowing the diesel to ignite the largest range of liquid ammonia most effectively, thereby obtaining the highest thermal efficiency. In addition, closing the opposite side nozzles or setting a nozzle height difference are auxiliary optimization measures to further ensure the independence of the fuel jet space and avoid negative interference.

[0027] In summary, this invention cleverly controls the interaction between the two fuels in the combustion chamber through a specific spatial layout of "central liquid ammonia and slightly offset diesel fuel," ultimately achieving efficient and reliable combustion of liquid ammonia and significantly improving the engine's thermal efficiency and emission performance.

[0028] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A diesel-ammonia engine injection structure, comprising an engine combustion chamber (1), an intake manifold (2) and an exhaust manifold (3) disposed on its cylinder head, and a dual direct injection fuel injection assembly mounted on the upper end of the cylinder head, wherein the lower end injection port of the dual direct injection fuel injection assembly extends into the engine combustion chamber (1), characterized in that: The dual direct injection fuel injection assembly includes a liquid ammonia injector (4) and a diesel injector (5). The liquid ammonia injector (4) is centrally located and coincides with the axis of the engine combustion chamber (1); The diesel injector (5) is arranged parallel to the side of the liquid ammonia injector (4), and there is a horizontal offset L between the horizontal axis of the diesel injector (5) and the horizontal axis of the liquid ammonia injector (4).

2. The diesel-ammonia engine injection structure according to claim 1, characterized in that, The liquid ammonia injector (4) and the diesel injector (5) are each equipped with a nozzle (6) at one end inside the engine combustion chamber (1). The nozzle (6) has multiple spray holes evenly distributed in the circumference.

3. The diesel-ammonia engine injection structure according to claim 2, characterized in that, The nozzles (6) of the liquid ammonia injector (4) and the diesel injector (5) are installed in the same direction, and there is no angle difference between their nozzles.

4. The diesel-ammonia engine injection structure according to claim 3, characterized in that, The nozzles (6) of the liquid ammonia injector (4) and the diesel injector (5) each have ten circumferentially distributed nozzle holes, and at least one nozzle hole on the opposite side of the two nozzles (6) is closed.

5. The diesel-ammonia engine injection structure according to claim 1, characterized in that, The horizontal offset L ranges from 8mm to 12mm.

6. The diesel-ammonia engine injection structure according to claim 5, characterized in that, The horizontal offset L is 10mm.

7. The diesel-ammonia engine injection structure according to claim 1, characterized in that, There is a height difference between the nozzles (6) at the lower end of the liquid ammonia injector (4) and the diesel injector (5), so that the oil jets (7) sprayed by the two injectors are at different horizontal levels.

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