Diesel combustion system and method of determining the same

Abstract

This invention provides a diesel engine combustion system and its determination method, relating to the field of diesel engine technology. The diesel engine combustion system includes a cylinder head, cylinder liner, piston, and fuel injector. The piston is housed within the cylinder liner, and the piston, cylinder liner, and cylinder head together form a combustion chamber. The fuel injector is housed within the cylinder head and is used to inject fuel into the combustion chamber. When the piston reaches top dead center of compression, the clearance volume between it and the cylinder head is V1, the piston cup volume is V2, and the cup volume ratio Vk is V2 / (V1+V2), with Vk ranging from 0.5 to 0.8.

Description

Technical Field

[0001] This invention relates to the field of diesel engine technology, and in particular to a diesel engine combustion system and its determination method. Background Technology

[0002] Large-bore diesel engines, due to their high speeds, have shorter absolute mixing time for fuel and air per cylinder cycle, resulting in slower combustion. This is especially true for high-speed engines with high power density and stringent performance requirements. To ensure power output, more diesel fuel needs to be injected into the cylinder per cycle, making it more difficult to achieve in-cylinder diesel spray evaporation mixing and rapid combustion. Furthermore, large-bore diesel engines typically have higher heat loads within the cylinder due to the greater number of cycles per unit time.

[0003] For small-bore automotive diesel engines, based on publicly available combustion organization methods and combustion chamber structures, methods such as intake turbulence, high-pressure diesel injection, and swirling combustion chambers can be fully utilized to promote diesel spray mixing and combustion within the cylinder. However, for large-bore diesel engines, on the one hand, due to the large cylinder diameter, the swirl formed through the intake manifold is easily dissipated during compression; on the other hand, because the cylinder diameter of a diesel engine is larger than that of an automotive diesel engine, the combustion chamber surface-to-volume ratio is small, heat transfer is poor, and the heat load on heated components such as the piston is high. To ensure reliability, the combustion chamber usually needs to avoid swirling combustion chamber structures with localized hot spots. Therefore, it is difficult for diesel engines to adopt the combustion organization methods of automotive diesel engines.

[0004] Large-bore, medium-speed diesel engines have relatively low speeds and longer fuel-air mixing time per cycle, resulting in higher thermal efficiency compared to conventional diesel engines. However, their in-cylinder combustion speed is slow, the combustion duration is long, and the proportion of afterburning increases, leading to low combustion efficiency.

[0005] Therefore, it is necessary to propose a combustion system and its design method suitable for high power density diesel engines. How to organize the fuel system and turbocharging system to quickly combust and mix within the design capacity under the boundary conditions of controllable mechanical and thermal loads of heated components in the cylinder is the key and difficult point for diesel engines to achieve high thermal efficiency. Summary of the Invention

[0006] The purpose of this invention is at least to provide a diesel engine combustion system and its determination method, so as to adapt to a large-bore, high-speed diesel engine.

[0007] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0008] One embodiment of the present invention provides a diesel engine combustion system, which includes a cylinder head, a cylinder liner, a piston, and a fuel injector. The piston is placed inside the cylinder liner, and the piston, cylinder liner, and cylinder head surround each other to form a combustion chamber. The fuel injector is placed inside the cylinder head and is used to inject fuel into the combustion chamber.

[0009] When the piston moves to the top dead center of compression, the clearance volume between it and the cylinder head is V1, the volume of the piston cup is V2, the cup volume ratio Vk is V2 / (V1+V2), and the range of Vk is 0.5-0.8.

[0010] In some embodiments, the piston bowl is ω-shaped, and Vk ranges from 0.6 to 0.7.

[0011] In some embodiments, an intake manifold and an exhaust manifold are provided inside the cylinder head, and the intake manifold and exhaust manifold are connected to the combustion chamber. An intake vortex is formed inside the intake manifold, and the intake vortex ratio is 0.2-0.5.

[0012] In some embodiments, the injector is disposed on the central axis of the cylinder head, and the number of fuel jets injected by the injector is 6-10.

[0013] In some embodiments, the liquid phase penetration distance of a single fuel jet injected by the injector at the start of combustion is S1, the maximum distance between the injector nozzle outlet and the piston is S2, the penetration ratio Sk is the ratio of S1 to S2, and the penetration ratio Sk ranges from 0.2 to 0.5.

[0014] One embodiment of the present invention provides a method for determining a diesel engine combustion system. The method is used to determine the diesel engine combustion system involved in the above embodiments, and the method includes: A1. Based on a one-dimensional thermodynamic simulation model of a diesel engine, a one-dimensional simulation analysis is performed to determine the combustion system scheme and target heat release rate curve with the goal of maximizing thermal efficiency. The combustion system scheme includes compression ratio, valve train scheme, and intake and exhaust flow coefficients.

[0015] A2. Based on the overall combustion system scheme, a three-dimensional simulation analysis is conducted. With mechanical load, thermal load and emission requirements as design boundaries and the target heat release rate curve as the objective, the intake swirl ratio, combustion chamber profile scheme and nozzle parameters are determined.

[0016] A3, with intake and exhaust flow coefficients and intake swirl ratio as targets, determines the intake and exhaust duct scheme that meets the requirements based on three-dimensional flow steady-state simulation calculations.

[0017] A4. Based on the nozzle parameters, the internal flow simulation calculation of the nozzle is performed, and the test nozzle parameters are determined by the degree of oil injection breakage.

[0018] A5, based on the intake and exhaust port scheme, valve distribution scheme, combustion chamber profile scheme and test nozzle parameters, conducts single-cylinder engine test verification to determine the test combustion system scheme that meets mechanical heat load requirements and thermal efficiency requirements while meeting emission requirements.

[0019] A6. Based on the experimental combustion system scheme, conduct whole-machine test verification to determine the final combustion system scheme that meets the performance requirements of the whole machine.

[0020] In some embodiments, A2 includes: A21, three-dimensional simulation analysis was carried out within the crankshaft angle range from the intake valve closing time (IVC) to the exhaust valve opening time (EVO). Combustion chamber profile schemes were designed based on different compression ratios. The clearance height, opening angle, and piston cup opening diameter of each combustion chamber profile scheme were kept consistent. The final compression ratio was selected by comparison.

[0021] A22, based on the final compression ratio, the clearance volume, opening angle, and piston cup opening diameter of the combustion chamber profile scheme were adjusted, and the experimental combustion chamber profile scheme was selected through comparison.

[0022] A23, based on the experimental combustion chamber profile scheme, conduct simulation analysis of different intake swirl ratios and different nozzle parameters, and compare and screen the experimental intake swirl ratios and experimental nozzle parameters.

[0023] In some embodiments, S4 includes: Based on the test nozzle parameters, including the injection duration, different nozzle parameters are determined to meet the injection duration requirements. The influence of different nozzle parameters on the degree of injection breakage is simulated and analyzed to determine the test nozzle parameters.

[0024] In some embodiments, S5 includes: Based on the intake and exhaust port scheme, valve train scheme, test combustion chamber profile scheme, and test nozzle parameters, a single-cylinder engine test was conducted to verify the different intake and exhaust boundary conditions obtained from one-dimensional thermodynamic simulation calculations.

[0025] If the thermal efficiency does not meet the requirements, the one-dimensional and three-dimensional thermal simulation models in A1 and A2 are calibrated respectively based on the single-cylinder engine test results. The heat release rate curves of the single-cylinder engine test and simulation are compared, and the compression ratio, combustion chamber profile, and nozzle parameters are iteratively optimized until the thermal efficiency meets the requirements.

[0026] In some embodiments, A6 includes: if the test combustion system scheme does not meet the overall performance indicators, modifying the one-dimensional thermodynamic simulation model and iteratively optimizing it based on the overall test results until the test combustion system scheme meets the overall performance indicators. Attached Figure Description

[0027] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related properties or features may have the same or similar reference numerals. Wherein: Figure 1 This is a structural schematic diagram of a diesel engine combustion system according to some embodiments.

[0028] Figure 2 This is a flowchart illustrating a method for determining a diesel engine combustion system according to some embodiments.

[0029] Figure 3 This is a schematic diagram of the in-cylinder parameters of a diesel engine combustion system according to some embodiments.

[0030] Figure 4 This is a schematic diagram of the nozzle parameters of a diesel engine combustion system according to some embodiments.

[0031] Explanation of reference numerals in the attached figures: 1-Cylinder head; 2-Cylinder liner; 3-Piston; 4-Injector; 11-Intake duct; 12-Exhaust passage; V1 - Clearance volume; V2 - Piston cup volume; S1 - Liquid phase penetration distance; S2 - Maximum distance between the nozzle outlet and the piston; h - clearance height; α - Opening angle; d - Piston cup opening diameter. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0033] It should be understood that the terms “system,” “device,” “unit,” and / or “module” used herein are one method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other words can achieve the same purpose, they may be replaced by other expressions.

[0034] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0035] It is understood that the technical terms that may be used in the description of this specification, such as “center,” “longitudinal,” “lateral,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the implementation method and do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the invention.

[0036] It should be noted that the use of terms such as "first" and "second" to define features in this document is merely for the purpose of distinguishing the corresponding features. Unless otherwise stated, these terms have no special meaning and should not be construed as limiting the scope of protection of this invention. As shown in this specification and claims, the terms "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural, unless the context clearly indicates otherwise. Generally, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, and these steps and elements do not constitute an exclusive list; the method or apparatus may also include other steps or elements.

[0037] In the description of this specification, it should also be noted that, unless otherwise expressly specified or limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium, or a connection within two components, etc. Those skilled in the art can understand the specific meaning of the above terms in this specification according to the specific circumstances.

[0038] To overcome the shortcomings of the prior art, this specification proposes a highly reliable and efficient combustion system adapted to large-bore, high-speed diesel engines (such as marine diesel engines). This combustion system achieves high thermal efficiency operation of high-power-density marine high-speed diesel engines while meeting emission, mechanical load, and thermal load requirements.

[0039] like Figure 1 As shown, the diesel engine combustion system includes a cylinder head 1, a cylinder liner 2, a piston 3, and a fuel injector 4.

[0040] The piston 3 is movably placed inside the cylinder liner 2, and the top surface of the piston 3, the inner wall of the cylinder liner 2, and the bottom surface of the cylinder head 1 together form a combustion chamber.

[0041] The fuel injector 4 is installed inside the cylinder head 1 and is used to inject fuel required for combustion into the combustion chamber. In some embodiments, the fuel injector 4 includes a nozzle that is disposed toward the combustion chamber and whose central axis coincides with the central axis of the cylinder liner 2.

[0042] The cylinder head 1 is also provided with an intake passage 11 and an exhaust passage 12. The intake passage 11 and the exhaust passage 12 are connected to the combustion chamber. An intake vortex can be formed in the intake passage 11 to promote the formation of a uniform air-fuel mixture. Excess gas produced by combustion in the combustion chamber is discharged from the exhaust passage 12.

[0043] To balance the uniformity of fuel distribution within the cylinder with the requirements of thermal load control, this manual features a special design for the combustion chamber volume distribution. When piston 3 reaches top dead center of compression, the volume of the space between the top surface of piston 3 and the bottom surface of cylinder head 1, excluding the piston cup, is defined as the clearance volume V1. The volume of the piston cup recessed at the top of piston 3 is defined as V2. The cup volume ratio Vk = V2 / (V1+V2), and Vk ranges from 0.5 to 0.8 (e.g., 0.6-0.7). This combustion chamber volume distribution parameter design ensures that most of the fuel is confined within the piston cup for mixing and combustion, reducing fuel-induced wall wetting and carbon buildup problems caused by fuel hitting the walls, while also preventing excessive localized thermal loads caused by an excessively high piston cup volume ratio.

[0044] In some embodiments, the piston 3 cup is ω-shaped, which has no obvious sharp edges and corners compared to an irregularly shaped combustion chamber, thus avoiding the generation of local hot spots. In this case, the value of Vk is in the range of 0.6-0.7, which can further improve the fuel-air mixing efficiency and reduce the risk of piston 3 thermal load.

[0045] In some embodiments, the intake swirl ratio is 0.2-0.5 (e.g., 0.3-0.4). This swirl intensity ensures effective radial mixing of the oil and gas while avoiding the problem of overlapping adjacent oil jets and deteriorated combustion caused by excessively strong swirls.

[0046] In some embodiments, the number of fuel jets injected by the injector 4 is 6-10 (e.g., 7-9 jets), which is adapted to the combustion chamber space of large-bore engines and ensures uniform fuel distribution.

[0047] In some embodiments, the injector 4 injects fuel into the cylinder at 30°CA to ensure power output. The liquid phase penetration distance of a single fuel jet injected by the injector 4 at the start of combustion is defined as S1, the maximum distance between the nozzle outlet of the injector 4 and the top surface of the piston 3 is S2, the penetration ratio Sk = S1 / S2, and the value of Sk ranges from 0.2 to 0.5 (e.g., 0.3 to 0.4). With this parameter matching, the spray jet has sufficient fragmentation and will not directly impact the piston 3 wall, which can reduce the thermal load on the piston 3 while ensuring rapid mixing.

[0048] This specification also provides a method for determining a diesel engine combustion system, used to determine or obtain the diesel engine combustion system described in the above embodiments. The method for determining the diesel engine combustion system ensures the reliability and performance compliance of the final solution through multi-dimensional simulation iteration combined with multiple rounds of experimental verification.

[0049] like Figure 2 As shown, method 200 includes A1-A6.

[0050] A1. Based on a one-dimensional thermodynamic simulation model of a diesel engine, a one-dimensional simulation analysis is performed to determine the combustion system scheme and target heat release rate curve with the goal of maximizing thermal efficiency. The combustion system scheme includes compression ratio, valve train scheme, and intake and exhaust flow coefficients.

[0051] In some embodiments, A1 also predefines the capability boundaries of the turbocharging system and the fuel system, and determines boundary limits such as the maximum combustion pressure, turbocharger ratio, and diesel injection pressure to avoid subsequent schemes exceeding the design capabilities of each system.

[0052] A2, based on the overall combustion system design, conducts three-dimensional simulation analysis, using mechanical load, thermal load, and emission requirements as design boundaries, and the target heat release rate curve as the optimization objective, to determine the intake swirl ratio, combustion chamber profile, and nozzle parameters. A2 specifically includes: A21, a three-dimensional simulation analysis was conducted within the crankshaft angle range from the intake valve closing moment (IVC) to the exhaust valve opening moment (EVO). Based on different compression ratios, corresponding combustion chamber profile schemes were designed, controlling the clearance height h, vent angle α, and piston cup opening diameter d (e.g., ...) of each combustion chamber profile scheme. Figure 3 As shown in the figure, the compression ratio is consistent with that of the parameters shown in the figure. Irrelevant parameters are excluded from interference, and the optimal final compression ratio is selected by comparison.

[0053] A22, based on the final compression ratio, adjust the clearance volume, opening angle, and piston cup opening diameter of the combustion chamber profile scheme, and compare and select the experimental combustion chamber profile scheme with the best thermal efficiency.

[0054] A23, based on the experimental combustion chamber profile scheme, conducted simulation analysis on different intake swirl ratios and different nozzle parameters, and compared and selected the experimental intake swirl ratios and experimental nozzle parameters. Among them, the nozzle parameters include the number of nozzles, nozzle diameter, injection angle, nozzle extension height, injection duration, and injection rate curve.

[0055] A3, with intake and exhaust flow coefficients and intake swirl ratio as targets, determined the intake and exhaust duct scheme 12 that meets the requirements based on three-dimensional flow steady-state simulation calculation.

[0056] The intake and exhaust duct 12 scheme includes the manifold design of the intake and exhaust duct 12 and the structural parameters of the intake and exhaust valves.

[0057] Specifically, considering structural layout and reliability constraints, at least three intake and exhaust duct schemes 12 that meet the requirements are determined. The implementation of intake and exhaust flow coefficients and intake swirl ratio can be verified through an air duct steady-state flow test platform. If the requirements are not met, the three-dimensional flow model is recalibrated, and the manifold design of intake and exhaust duct 12 and the structural parameters of intake and exhaust valves are optimized until the requirements are met.

[0058] A4. Based on the nozzle parameters, the internal flow simulation calculation of the nozzle is carried out, and the experimental nozzle parameters are determined with the degree of oil injection breakage as the optimization target.

[0059] Specifically, based on the injection duration requirement in the test nozzle parameters, different nozzle structure parameters that meet the injection duration requirement (such as...) are selected. Figure 4 As shown, the parameters include nozzle length, nozzle inlet diameter, nozzle outlet diameter, and inlet radius. First, feasible solutions are screened through RANS simulation. Then, the influence of different nozzle solutions on the degree of fuel injection breakage is analyzed through large eddy simulation (LES simulation). Finally, at least three nozzle solutions with the best breakage effect are determined as the test nozzle parameters.

[0060] A5, based on the intake and exhaust port 12 scheme, valve train scheme, combustion chamber profile scheme and test nozzle parameters, conducts single-cylinder engine test verification. Considering the consistency of each cylinder of the whole engine, the difference between intake and exhaust pressure and temperature and single-cylinder engine, redundancy is set to determine the test combustion system scheme that meets the emission requirements, mechanical heat load requirements and thermal efficiency requirements at the same time.

[0061] If the thermal efficiency does not meet the requirements, the one-dimensional and three-dimensional thermal simulation models in A1 and A2 are calibrated respectively based on the single-cylinder engine test results. The heat release rate curves of the single-cylinder engine test and simulation are compared, and the compression ratio, combustion chamber profile, and nozzle parameters are iteratively optimized until the thermal efficiency meets the requirements.

[0062] A6. Based on the experimental combustion system scheme obtained in A5, conduct whole-machine test verification to determine the final combustion system scheme that meets the performance requirements of the whole machine.

[0063] If the test combustion system design does not meet the overall engine performance indicators, the one-dimensional thermodynamic simulation model is modified and iteratively optimized based on the overall engine test results. Specifically, the deviation between the overall engine intake and exhaust pressure conditions and the one-dimensional thermodynamic simulation model is analyzed, and the consistency of each cylinder, intake vacuum, exhaust back pressure, etc. are analyzed until the test combustion system design meets the overall engine performance indicators.

[0064] The combustion system described in this manual is designed to match multiple parameters, such as piston cup ratio, swirl ratio, and penetration ratio, to suit the operating characteristics of large-bore, high-speed diesel engines. A piston cup ratio of 0.5 to 0.8 ensures efficient mixing and combustion of most of the fuel within the piston cup while avoiding localized heat load concentration. An intake swirl ratio of 0.2 to 0.5 enhances fuel-air mixing without causing fuel jet overlap. A penetration ratio of 0.2 to 0.5 ensures complete fuel breakup while reducing the risk of fuel hitting the piston walls, ultimately improving combustion efficiency while controlling thermal and mechanical loads.

[0065] The combustion system determination method provided in this manual adopts a multi-level iterative process of "one-dimensional simulation to determine the overall boundary - three-dimensional simulation to determine the cylinder parameters - internal flow simulation to determine the injection hole scheme - single-cylinder test to verify performance - whole-machine test to verify adaptability". This process not only ensures the rationality of the design parameters, but also reduces the risk of implementation through multiple rounds of test verification. Compared with traditional experience-based design methods, it can shorten the development cycle and ensure that the final solution meets multiple requirements of thermal efficiency, emissions and reliability.

[0066] The basic concepts have been described above. It is clear that the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification, especially for those skilled in the art. Furthermore, unless expressly stated in the claims, the order of elements and sequences, the use of numbers and letters, or other names in this specification are not intended to limit the order of the processes and methods described herein. Although various examples of currently considered useful embodiments of the invention have been discussed in the foregoing disclosure, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments described herein.

Claims

1. A diesel combustion system characterized by, The combustion system includes a cylinder head, a cylinder liner, a piston, and a fuel injector. The piston is placed inside the cylinder liner, and the piston, the cylinder liner, and the cylinder head surround each other to form a combustion chamber. The fuel injector is placed inside the cylinder head and is used to inject fuel into the combustion chamber. When the piston moves to the top dead center of compression, the clearance volume between it and the cylinder head is V1, the internal volume of the piston cup is V2, the cup volume ratio Vk is V2 / (V1+V2), and the range of Vk is 0.5-0.

8.

2. The diesel engine combustion system according to claim 1, characterized in that, The piston bowl is ω-shaped, and the Vk range is 0.6-0.

7.

3. The diesel engine combustion system according to claim 1, characterized in that, The cylinder head is provided with an intake passage and an exhaust passage, which are connected to the combustion chamber. An intake vortex is formed in the intake passage, and the intake vortex ratio is 0.2-0.

5.

4. The diesel engine combustion system according to claim 1, characterized in that, The injector is located on the central axis of the cylinder head, and the number of fuel jets injected by the injector is 6-10.

5. The diesel engine combustion system according to claim 4, characterized in that, At the start of combustion, the liquid phase penetration distance of a single fuel jet injected by the injector is S1, the maximum distance between the injector nozzle outlet and the piston is S2, and the penetration ratio Sk is the ratio of S1 to S2, with the penetration ratio Sk ranging from 0.2 to 0.

5.

6. A method for determining a diesel engine combustion system, characterized in that, The determination method is used to determine the diesel engine combustion system according to any one of claims 1-5, and the determination method includes: A1. Based on a one-dimensional thermodynamic simulation model of a diesel engine, a one-dimensional simulation analysis is performed to determine the combustion system scheme and the target heat release rate curve with the goal of maximizing thermal efficiency. The combustion system scheme includes compression ratio, valve train scheme, and intake and exhaust flow coefficients. A2. Based on the overall combustion system scheme, a three-dimensional simulation analysis is performed. With mechanical load, thermal load and emission requirements as design boundaries and the target heat release rate curve as the objective, the intake swirl ratio, combustion chamber profile scheme and nozzle parameters are determined. A3. Based on the intake and exhaust flow coefficients and the intake swirl ratio as targets, and using three-dimensional flow steady-state simulation calculations, determine the intake and exhaust duct schemes that meet the requirements. A4. Based on the nozzle parameters, perform internal flow simulation calculations within the nozzle to determine the test nozzle parameters according to the degree of oil injection breakage. A5. Based on the intake and exhaust port scheme, the valve train scheme, the combustion chamber profile scheme, and the test nozzle parameters, a single-cylinder engine test was conducted to verify and determine a test combustion system scheme that meets the mechanical heat load requirements and thermal efficiency requirements while meeting emission requirements. A6. Based on the aforementioned experimental combustion system scheme, conduct whole-machine testing and verification to determine the final combustion system scheme that meets the overall performance requirements.

7. The method for determining a diesel engine combustion system according to claim 6, characterized in that, A2 include: A21, a three-dimensional simulation analysis is carried out within the crankshaft angle range from the intake valve closing moment (IVC) to the exhaust valve opening moment (EVO). Based on different compression ratios, combustion chamber profile schemes are designed, and the clearance height, opening angle, and piston cup opening diameter of each combustion chamber profile scheme are controlled to be consistent. The final compression ratio is selected by comparison. A22, Based on the final compression ratio, adjust the clearance volume, opening angle, and piston cup opening diameter of the combustion chamber profile scheme, and compare and select the experimental combustion chamber profile scheme; A23. Based on the aforementioned test combustion chamber profile scheme, simulation analysis was conducted on different intake swirl ratios and different nozzle parameters to compare and select the test intake swirl ratios and test nozzle parameters.

8. The method for determining a diesel engine combustion system according to claim 7, characterized in that, A4 include: Based on the test nozzle parameters, including the injection duration, different nozzle parameters required for the injection duration are determined, and the influence of the different nozzle parameters on the degree of injection breakage is simulated and analyzed to determine the test nozzle parameters.

9. The method for determining a diesel engine combustion system according to claim 7, characterized in that, A5 includes: Based on the aforementioned intake and exhaust port scheme, the aforementioned valve train scheme, the aforementioned test combustion chamber profile scheme, and the aforementioned test nozzle parameters, a single-cylinder engine test was conducted to verify the different intake and exhaust boundary conditions obtained from one-dimensional thermodynamic simulation calculations. If the thermal efficiency does not meet the requirements, the one-dimensional and three-dimensional thermal simulation models in A1 and A2 are calibrated respectively based on the single-cylinder engine test results. The heat release rate curves of the single-cylinder engine test and simulation are compared, and the compression ratio, combustion chamber profile, and nozzle parameters are iteratively optimized until the thermal efficiency meets the requirements.

10. The method for determining a diesel engine combustion system according to claim 7, characterized in that, A6 includes: If the experimental combustion system scheme fails to meet the overall performance indicators, the one-dimensional thermodynamic simulation model is modified and iteratively optimized based on the overall test results until the experimental combustion system scheme meets the overall performance indicators.

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