Method and system for controlling combustion deviation between diesel engine cylinders and diesel engine

Abstract

The invention provides a diesel engine inter-cylinder combustion deviation control method and system and a diesel engine, and the method comprises the steps that a mirror symmetry air inlet system is constructed, and computational fluid dynamics simulation optimization is conducted on the air inlet system, so that the air inflow deviation of each cylinder is smaller than a preset threshold value; performing exhaust gas recirculation gas distribution uniformity simulation on the basis of the optimized gas inlet system, and if the distribution difference value is not smaller than the preset threshold value, adjusting arrangement position parameters of an EGR pipeline in the gas inlet system to obtain an exhaust gas optimized gas inlet system; controlling the compression ratio of each cylinder within the range of a target value based on the manufacturing and assembling tolerance of the exhaust gas optimized air inlet system; calculating the theoretical oil injection quantity of each cylinder according to each cylinder with the compression ratio controlled within the target value range, and selecting a median flow oil nozzle based on the theoretical oil injection quantity to ensure that the oil injection quantity deviation of the oil injectors of each cylinder under the same injection pressure is smaller than a third preset threshold value; the combustion phases of the cylinders are synchronous, and the combustion process is more sufficient.

Description

Technical Field

[0001] This invention belongs to the field of diesel engine technology, and specifically relates to a method, system and diesel engine for controlling inter-cylinder combustion deviation in a diesel engine. Background Technology

[0002] As a type of compression-ignition internal combustion engine, the performance optimization of diesel engines has always revolved around two core objectives: improving thermal efficiency and reducing emissions. Currently, significant progress has been made in research addressing issues such as slow air-fuel mixing rates and long combustion durations in single-cylinder engines. However, in multi-cylinder diesel engines, uneven combustion between cylinders remains a core technical challenge hindering further improvements in overall performance.

[0003] A search revealed that existing related technical solutions mostly focus on the diagnosis and post-processing adjustment of uneven combustion. The most similar existing technology is a method based on online near-field noise monitoring. This method analyzes engine noise data under different calibration parameters to determine whether uneven combustion exists and prompts engineers to perform calibration optimization in order to improve combustion uniformity and enhance engine sound quality.

[0004] However, this approach has significant drawbacks: it can only passively identify problems and attempt to compensate for inherent defects in hardware or basic design through software calibration, which is a temporary and indirect approach. It cannot fundamentally solve the problem of inter-cylinder combustion deviations caused by inconsistencies in the intake system, EGR system, mechanical manufacturing tolerances, and the fuel injection system itself.

[0005] Therefore, the purpose of this invention is to fundamentally and proactively eliminate the root cause of inter-cylinder combustion deviation. By systematically optimizing four physical aspects—intake uniformity, EGR uniformity, compression ratio consistency, and fuel injection consistency—it provides a novel solution for achieving efficient, clean, and stable operation of diesel engines. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method, system, and diesel engine for controlling inter-cylinder combustion deviation in a diesel engine, thereby resolving the technical issues in the prior art.

[0007] On the one hand, the invention provides the following technical solution: a method for controlling inter-cylinder combustion deviation in a diesel engine, the method comprising: constructing a mirror-symmetric intake system and performing computational fluid dynamics simulation optimization on the intake system to make the intake volume deviation of each cylinder of the diesel engine less than a first preset threshold. Based on the optimized intake system, the uniformity of exhaust gas recirculation distribution is simulated to evaluate the difference in quantity and quality of exhaust gas recirculation gas that can be obtained between cylinders, and to determine whether the distribution difference is less than a second preset threshold. If the distribution difference is not less than the second preset threshold, then adjust the arrangement position parameters of the EGR pipeline in the intake system until the distribution difference is less than the second preset threshold to obtain an exhaust gas optimization intake system. Based on the exhaust gas optimization intake system, the manufacturing and assembly tolerances of one or more key components, such as the control connecting rod, crankshaft, and cylinder bore, are modified to control the compression ratio of each cylinder within the target range. Based on the compression ratio of each cylinder within the target range, calculate the theoretical injection quantity of each cylinder, and select the median flow nozzle based on the theoretical injection quantity to perform injection quantity calibration, ensuring that the injection quantity deviation of each cylinder injector under the same injection pressure is less than the third preset threshold. By coordinating all the above steps, combustion deviations between cylinders of the diesel engine are reduced.

[0008] Compared to existing technologies, the advantages of this application are as follows: by constructing a mirror-symmetric intake system and optimizing it using CFD simulation, the uniformity of intake air in each cylinder is ensured (deviation <2.5%); combined with the selection and precise calibration of median flow fuel injectors, the injection quantity of each cylinder is guaranteed to be highly consistent (deviation <1%). This ensures that the combustion phase of each cylinder is synchronized, resulting in a more complete combustion process. Implementation results show that the effective thermal efficiency of a diesel engine can be increased by 1%~1.5%, and fuel consumption can be reduced by 2%~3%; taking a 2.5L diesel engine as an example, its thermal efficiency can reach 45%, an improvement of 8%-10% compared to traditional designs.

[0009] Furthermore, the construction of the mirror-symmetrical intake system includes: an intake manifold and a plurality of mirror-symmetrical intake manifolds, wherein the intake manifold is configured as the central intake layout of the intake system so that the intake airflow directions of the two intake manifolds symmetrical to the intake manifold are completely symmetrical.

[0010] Furthermore, the computational fluid dynamics simulation optimization of the intake system includes: steady-state flow resistance simulation and transient intake process simulation; the first preset threshold is 2%-3%.

[0011] Furthermore, the optimization of the intake system also includes: adopting a gradient cross-section design at the connection between the intake manifold and the intake main pipe, and / or adding a length compensation section for the intake manifold that flows to the direction furthest from the intake main pipe.

[0012] Furthermore, adjusting the position parameters of the EGR pipe includes: adjusting at least one of the following: the inlet direction of the EGR pipe, the insertion depth into the intake manifold, and the angle. The second preset threshold is 4%-6%.

[0013] Furthermore, the control of the manufacturing and assembly tolerances includes: The length tolerance of each cylinder connecting rod is controlled within ±0.025mm; The cylindricity tolerance of the crankshaft journal is controlled within 5μm, and the surface roughness Ra≤0.15μm; The roundness tolerance of the cylinder bore is controlled within 3μm, and the cylindricity tolerance is controlled within 5μm.

[0014] Furthermore, it also includes verifying the consistency of compression ratio by measuring the piston protrusion height of each cylinder, ensuring that the difference in compression ratio between cylinders is within ±0.05.

[0015] Furthermore, the fuel injection quantity calibration also includes: Control the installation height of each cylinder injector so that the distance deviation between the nozzle end face and the top surface of the combustion chamber is within ±0.5mm; Control the injection angle of each cylinder's injector to be consistent; The flow coefficient of the median flow nozzle is the average of the flow coefficients of each cylinder injector; The third preset threshold is 0.5-1.5%.

[0016] Secondly, the invention provides the following technical solution: a control system for inter-cylinder combustion deviation in a diesel engine, the system comprising: The calculation module is used to construct a mirror-symmetric intake system and to perform computational fluid dynamics simulation optimization on the intake system so that the intake volume deviation of each cylinder of the diesel engine is less than a first preset threshold. The evaluation module is used to simulate the uniformity of exhaust gas recirculation gas distribution based on the optimized intake system, evaluate the distribution difference in quantity and quality of exhaust gas recirculation gas that can be obtained between cylinders, and determine whether the distribution difference is less than a second preset threshold. An adjustment module is used to adjust the arrangement parameters of the EGR pipeline in the intake system if the distribution difference is not less than the second preset threshold, until the distribution difference is less than the second preset threshold, thereby obtaining an exhaust gas optimized intake system. The control module is used to optimize the intake system based on the exhaust gas and modify the manufacturing and assembly tolerances of one or more key components such as the connecting rod, crankshaft, and cylinder bore in the cylinder block, so that the compression ratio of each cylinder is controlled within the target value range. The calibration module is used to calculate the theoretical fuel injection quantity of each cylinder based on the compression ratio controlled within the target value range, and select the median flow nozzle based on the theoretical fuel injection quantity to perform fuel injection quantity calibration, so as to ensure that the fuel injection quantity deviation of each cylinder injector under the same injection pressure is less than the third preset threshold. The reduction module is used to reduce combustion deviations between cylinders of a diesel engine by coordinating all the above steps.

[0017] Thirdly, the invention provides the following technical solution: a diesel engine, characterized in that it includes the aforementioned system. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the method for controlling inter-cylinder combustion deviation in a diesel engine according to the first embodiment of the present invention; Figure 2 This is a logic diagram of the diesel engine inter-cylinder combustion deviation control method according to the first embodiment of the present invention; Figure 3 This is a mirror-symmetrical air intake system according to the first embodiment of the present invention; Figure 4 This is a simulation of EGR uniformity in the first embodiment of the present invention. Figure 5 This is a structural block diagram of the control system for inter-cylinder combustion deviation in a diesel engine according to the third embodiment of the present invention; Figure 6 It is a traditional air intake system.

[0020] The embodiments of the present invention will be further described below with reference to the accompanying drawings. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain embodiments of the present invention, and should not be construed as limiting the present invention.

[0022] In the description of the embodiments of the present invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., 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 embodiments of the present invention and simplifying the description, 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 limitations on the present invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] Example 1 In the first embodiment of the present invention, please refer to Figures 1 to 4 As shown, a method for controlling inter-cylinder combustion deviation in a diesel engine includes the following steps S01 to S06: S01, construct a mirror-symmetric intake system and perform computational fluid dynamics simulation optimization on the intake system to make the intake volume deviation of each cylinder of the diesel engine less than a first preset threshold. Specifically, the constructed mirror-symmetrical intake system includes: an intake manifold and multiple mirror-symmetrical intake manifolds. The intake manifold is configured as the central intake layout of the intake system, so that the airflow directions of the two intake manifolds symmetrical to the intake manifold are completely symmetrical. The computational fluid dynamics simulation optimization of the intake system includes: steady-state flow resistance simulation and transient intake process simulation; the first preset threshold is 2%-3%. The optimization of the intake system also includes: using a gradient cross-section design at the connection between the intake manifold and the intake manifolds, and / or adding a length compensation section for the intake manifold furthest from the intake manifold.

[0025] This embodiment details the construction and computational fluid dynamics (CFD) optimization process of a mirror-symmetric intake system. The specific steps are as follows: 1. System construction; First, a mirror-symmetric air intake system is constructed. This system abandons the traditional asymmetrical air intake layout (see...). Figure 6 The core includes: Integrated intake manifold: An integrated intake manifold with a one-piece design.

[0026] Intermediate intake layout: The intake manifold is placed at the geometric center of the system to achieve intermediate intake.

[0027] Mirror-symmetrical intake manifolds: The intake manifolds of each cylinder are designed to be completely mirror-symmetrical. Using the central axis of the intake manifold as the axis of symmetry, the intake manifolds of cylinder 1 and cylinder 4 are symmetrical, and the intake manifolds of cylinder 2 and cylinder 3 are symmetrical, thus ensuring that the intake airflow path and direction of the symmetrical cylinders are completely consistent.

[0028] 2. CFD simulation optimization; Next, the constructed intake system is optimized using CFD simulation, a process that consists of two stages: Steady-state flow resistance simulation: First, CFD steady-state flow resistance simulation is performed. By continuously iterating and optimizing the shape and curvature inside the manifold, the goal is to minimize the flow resistance difference between cylinders (such as cylinder 1 and cylinder 2).

[0029] Transient intake process simulation: Then, CFD transient intake process simulation is performed to simulate the intake process within a complete engine working cycle and evaluate the intake mass flow rate of each cylinder. The target set in this embodiment is that the intake volume deviation of each cylinder is less than a first preset threshold (2.5%).

[0030] 3. Optimization measures; If the simulation results show that the intake volume deviation exceeds the threshold, the following optimization measures will be implemented: Manifold cross-section optimization: A gradually changing cross-section design is adopted at the connection between the intake manifold and the intake manifolds of each cylinder to reduce local flow resistance and ensure a consistent intake pressure gradient for each cylinder. CFD verification shows that this optimization can reduce pressure loss by 5% to 8% and reduce the impact of intake pulsation on cylinder uniformity.

[0031] Manifold length compensation: A spiral length compensation section is added to the manifold of cylinders that are far from the intake manifold (such as cylinders 1 and 4) to balance the intake pulse effect and flow path differences between cylinders.

[0032] 4. Verification results; After the above optimization, CFD transient simulation verified that the intake volume deviation of each cylinder can be stabilized at 2.3%, which meets the design requirement of less than 2.5%, proving the effectiveness of the mirror symmetry design and optimization method.

[0033] S02, based on the optimized intake system, perform exhaust gas recirculation gas distribution uniformity simulation, evaluate the distribution difference in quantity and quality of exhaust gas recirculation gas that can be obtained between cylinders, and determine whether the distribution difference is less than a second preset threshold. Optionally, adjusting the position parameters of the EGR pipe includes: adjusting at least one of the following: the inlet direction of the EGR pipe, the insertion depth into the intake manifold, and the angle. The second preset threshold is 4%-6%.

[0034] S03, if the distribution difference is not less than the second preset threshold, then adjust the arrangement position parameters of the EGR pipeline in the intake system until the distribution difference is less than the second preset threshold, and obtain the exhaust gas optimized intake system. This embodiment details the simulation evaluation and optimization process for the uniformity of the exhaust gas recirculation (EGR) system. The specific steps are as follows: 1. EGR uniformity simulation evaluation; Based on the optimized mirror-symmetric intake system, EGR uniformity simulation was performed. CFD simulation was used to analyze the mixing process of EGR gas and fresh air in the intake manifold, and the mass fraction distribution of EGR gas at the intake valves of each cylinder was evaluated. The objective set in this embodiment is that the EGR rate deviation of each cylinder is less than a second preset threshold (5%).

[0035] 2. Problem identification and optimization direction determination; Initial simulation results indicate a uniformity issue. For example, because the EGR pipe was initially inserted vertically into the intake manifold, the EGR concentration in cylinders 3 and 4 (average 12.5%) was significantly higher than that in cylinders 1 and 2 (average 10.8%), with a deviation of 15.7%, which does not meet the requirements.

[0036] Based on the non-uniformity of EGR distribution in each cylinder shown in the simulation results, the optimization direction is determined. For example, if the EGR concentration in one cylinder is significantly lower, the EGR pipe needs to be adjusted to favor that area.

[0037] 3. EGR tube optimization and adjustment measures; To improve uniformity, the layout parameters of the EGR pipeline are adjusted as follows: Adjust the EGR pipe inlet direction: Change the connection angle between the EGR pipe and the intake manifold. For example, adjust the inlet from vertical downward to tilt it about 30° towards the cylinder side with lower concentration (such as cylinders 1 and 2), so that the EGR airflow direction matches the fresh intake airflow better and promotes mixing.

[0038] Optimize EGR pipe insertion depth: Adjust the insertion depth into the intake manifold based on simulation results. For example, increase the EGR pipe insertion depth by 15mm to bring it closer to the airflow center, improving the mixing efficiency of EGR gas and air, especially for supplying the distal cylinders.

[0039] 4. Verification and iteration; A new round of CFD simulations was conducted on the adjusted EGR pipe positions to verify the EGR uniformity of each cylinder. After optimization, the results showed that the EGR concentration distribution in each cylinder was between 11.6% and 12.1%, with a maximum deviation of 4.3%, which is less than the 5% threshold and meets the design requirements. If it does not meet the requirements, the above optimization steps are repeated until the target is achieved.

[0040] This process, through directional optimization based on CFD simulation, effectively solves the problem of uneven EGR distribution among cylinders, providing a uniform gas basis for subsequent compression ratio and injection control.

[0041] S04, Based on the exhaust gas optimization intake system, modify the manufacturing and assembly tolerances of one or more key components such as the control connecting rod, crankshaft, and cylinder bore to control the compression ratio of each cylinder within the target value range; Specifically, the control of manufacturing and assembly tolerances includes: The length tolerance of each cylinder connecting rod is controlled within ±0.025mm; The cylindricity tolerance of the crankshaft journal is controlled within 5μm, and the surface roughness Ra≤0.15μm; The roundness tolerance of the cylinder bore is controlled within 3μm, and the cylindricity tolerance is controlled within 5μm.

[0042] Specifically, this also includes verifying the consistency of compression ratio by measuring the piston protrusion height of each cylinder, ensuring that the difference in compression ratio between cylinders is within ±0.05.

[0043] In this embodiment, to ensure the consistency of the mechanical compression ratio of each cylinder, the manufacturing tolerances and assembly process of key components affecting the compression ratio (connecting rod, crankshaft, cylinder block) must be strictly controlled, and verified through final measurement. The specific implementation method is as follows: 1. Manufacturing tolerance control for key components; Linkage length tolerance control: High-precision machining equipment (such as high-precision grinding machines) is used to ensure that the length tolerance of the center distance between the large and small holes of each cylinder connecting rod is strictly controlled within ±0.025mm.

[0044] During assembly, a group selection method is used to assemble connecting rods with very similar lengths onto the same engine to further reduce assembly errors.

[0045] Crankshaft journal dimensional tolerance control: The cylindricity tolerance of each main journal and connecting rod journal of the crankshaft is controlled to be within 5μm.

[0046] Ultra-precision machining ensures that the surface roughness Ra of the journal is ≤ 0.15μm.

[0047] Before assembly, the crankshaft is dynamically balanced to ensure that the concentricity and perpendicularity of each journal meet the design requirements.

[0048] Cylinder block and bore dimensional tolerance control: High-precision honing process is adopted to ensure that the roundness tolerance of the cylinder block and cylinder bore is within 3μm and the cylindricity tolerance is within 5μm.

[0049] During assembly, the cylinder bore dimensions of each cylinder are checked online to ensure consistency.

[0050] 2. Compression ratio consistency verification (piston protrusion height test); After assembly, the consistency of the compression ratio is finally verified by measuring the protrusion height of the pistons in each cylinder.

[0051] Measurement method: Use a dial indicator to measure the amount of protrusion of the piston top relative to the upper surface of the cylinder head when the piston is at top dead center.

[0052] Consistency requirement: In this embodiment, the difference in piston protrusion height between cylinders is required to be within ±0.05mm, thereby characterizing the consistency of compression ratio.

[0053] Result processing: If the piston protrusion height of a certain cylinder is obviously abnormal, the connecting rod, crankshaft and cylinder block dimensions of the corresponding cylinder need to be checked, and necessary rework or replacement should be carried out until the requirements are met.

[0054] Actual measurement results: The maximum difference in piston protrusion height data for each cylinder was 0.04mm, which meets the target requirements and proves the effectiveness of the above tolerance control method.

[0055] S05, calculate the theoretical fuel injection quantity of each cylinder based on the compression ratio controlled within the target value range, and select the median flow rate nozzle based on the theoretical fuel injection quantity to perform fuel injection quantity calibration, ensuring that the fuel injection quantity deviation of each cylinder injector under the same injection pressure is less than the third preset threshold. Specifically, the fuel injection quantity calibration also includes: Control the installation height of each cylinder injector so that the distance deviation between the nozzle end face and the top surface of the combustion chamber is within ±0.5mm; Control the injection angle of each cylinder's injector to be consistent; The flow coefficient of the median flow nozzle is the average of the flow coefficients of each cylinder injector; The third preset threshold is 0.5-1.5%.

[0056] In this embodiment, to achieve consistency in fuel injection quantity across cylinders and ensure fuel injection accuracy, this solution optimizes the process through two aspects: injector selection and calibration, and installation position control. The specific implementation steps are as follows: 1. Control of fuel injection quantity consistency; Theoretical fuel injection quantity calculation: Based on parameters such as compression ratio and intake volume that have been ensured to be consistent, the theoretical fuel injection quantity per cycle of each cylinder under the specific working conditions of this embodiment is calculated (approximately 55mg).

[0057] Selection of medium flow rate nozzles: A batch of fuel injectors were tested for flow rate to obtain the flow coefficient (Cd value) of each injector.

[0058] The nozzle with the average flow coefficient Cd value among all tested nozzles is selected as the median flow nozzle, thereby reducing the fuel injection quantity deviation between cylinders from the design source.

[0059] Fuel injection quantity calibration and verification: Install the selected median flow nozzles onto the injectors of each cylinder.

[0060] On the oil pump test bench, under the same injection pressure (e.g., 1800 bar), measure the actual injection quantity of each cylinder injector.

[0061] Objectives and Results: This embodiment requires that the fuel injection quantity deviation of each cylinder be less than the third preset threshold (1%). Calibration results show that the actual fuel injection quantity of each cylinder is between 54.7mg and 55.2mg, with a maximum deviation of 0.9%, which meets the requirements.

[0062] Adjustment measures: If the fuel injection quantity of a certain cylinder is found to be out of control during calibration, the injection pressure of the injector of that cylinder needs to be adjusted or the injector needs to be replaced.

[0063] 2. Injector installation position optimized; To ensure consistent fuel atomization and fuel-air mixture across all cylinders, precise control of the injector installation position is required. Installation height control: Use specialized depth gauges and other tools to ensure that the distance between the nozzle end face of each cylinder injector and the top surface of the combustion chamber is consistent, and control the height deviation within ±0.5mm.

[0064] Injection angle control: Custom tooling fixtures are used for assembly to ensure that the injection angle of each cylinder injector is completely consistent, so as to match the shape of the combustion chamber and the direction of internal airflow, ensuring that the fuel and air are fully mixed.

[0065] Through the above systematic measures, a high degree of consistency was achieved at both the fuel supply and injection status levels, providing a key guarantee for ultimately reducing inter-cylinder combustion deviation.

[0066] S06, by coordinating the execution of all the above steps, reduces combustion deviation between cylinders of the diesel engine.

[0067] The diesel engine, after undergoing all the above optimization processes, was subjected to performance testing on a test bench. The results showed that: Thermal efficiency: Combustion is more uniform in each cylinder, and the effective thermal efficiency reaches 45%, which is 1.2% higher than before optimization.

[0068] Emissions: Due to more complete combustion, particulate matter (PM) emissions were reduced by 12% and nitrogen oxide (NOx) emissions were reduced by 18%.

[0069] Vibration and noise: The maximum deviation of inter-cylinder combustion pressure has been reduced from 7 bar to 2.5 bar, which is far below the industry level, and the vibration and noise of the engine have been significantly reduced.

[0070] In summary, the method for controlling inter-cylinder combustion deviation in a diesel engine has the following effects: By constructing a mirror-symmetrical intake system and optimizing it using CFD simulation, the uniformity of intake air in each cylinder is ensured (deviation <2.5%). Combined with the selection and precise calibration of median flow injectors, the injection quantity in each cylinder is guaranteed to be highly consistent (deviation <1%). This synchronizes the combustion phase in each cylinder, resulting in a more complete combustion process. Implementation results show that this can improve the effective thermal efficiency of diesel engines by 1%~1.5% and reduce fuel consumption by 2%~3%. Taking a 2.5L diesel engine as an example, its thermal efficiency can reach 45%, an improvement of 8%-10% compared to traditional designs.

[0071] The uniformity of EGR distribution across cylinders (deviation <5%) and the consistency of air-fuel ratio fundamentally improve the combustion environment and effectively prevent incomplete combustion in certain areas. Experimental data confirms that it can synergistically reduce particulate matter (PM) emissions by 10%~15% and nitrogen oxide (NOx) emissions by 15%~20%, providing a reliable technical guarantee for meeting the "China VII" and higher emission regulations.

[0072] By strictly controlling the consistency of compression ratio (piston protrusion height difference < ±0.05mm) and fuel injection consistency, the combustion pressure of each cylinder is made extremely close. This invention can control the maximum deviation of inter-cylinder combustion pressure to below 3 bar, which is significantly better than the industry level of 5-8 bar. It fundamentally eliminates vibration and noise caused by uneven power output of each cylinder, and greatly improves the NVH performance of the entire vehicle.

[0073] This application focuses on refining and digitally optimizing existing design and manufacturing processes (such as CFD simulation-driven design and tightening critical tolerances) without adding expensive new hardware or complex processes. This concept, based on forward design and precision manufacturing, achieves a performance leap while maintaining cost competitiveness, possessing extremely high industrialization value and market potential.

[0074] The reduction in inter-cylinder combustion deviation makes the thermal and mechanical load distribution of each cylinder more balanced, avoiding long-term overload operation of individual cylinders, effectively extending the engine overhaul cycle and service life, and improving the product's market competitiveness.

[0075] Example 2 like Figure 5 As shown, a second embodiment of the present invention provides a control system for inter-cylinder combustion deviation in a diesel engine, the system comprising: The construction module 10 is used to construct a mirror-symmetric intake system and perform computational fluid dynamics simulation optimization on the intake system so that the intake volume deviation of each cylinder of the diesel engine is less than a first preset threshold. Evaluation module 20 is used to simulate the uniformity of exhaust gas recirculation gas distribution based on the optimized intake system, evaluate the distribution difference in quantity and quality of exhaust gas recirculation gas that can be obtained between cylinders, and determine whether the distribution difference is less than a second preset threshold. The adjustment module 30 is used to adjust the arrangement position parameters of the EGR pipeline in the intake system if the distribution difference is not less than the second preset threshold, until the distribution difference is less than the second preset threshold, thereby obtaining an exhaust gas optimized intake system. Control module 40 is used to modify the manufacturing and assembly tolerances of one or more key components, such as the control connecting rod, crankshaft, and cylinder bore, based on the exhaust gas optimization intake system, so that the compression ratio of each cylinder is controlled within the target value range. The calibration module 50 is used to calculate the theoretical fuel injection quantity of each cylinder based on the compression ratio controlled within the target value range, and select the median flow nozzle based on the theoretical fuel injection quantity to perform fuel injection quantity calibration, so as to ensure that the fuel injection quantity deviation of each cylinder injector under the same injection pressure is less than the third preset threshold. The reduction module 60 is used to reduce combustion deviations between cylinders of the diesel engine by coordinating the execution of all the above steps.

[0076] The control system for inter-cylinder combustion deviation of diesel engine provided in this embodiment of the invention has the same implementation principle and technical effect as the aforementioned method embodiment. For the sake of brevity, any parts not mentioned in the system embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0077] Example 3 This embodiment provides a diesel engine that uses the system described in Embodiment 2, thereby having the ability to fundamentally reduce inter-cylinder combustion deviation.

[0078] The diesel engine includes: the engine body, including conventional structures such as the cylinder block, crankshaft, connecting rods, pistons, and cylinder head.

[0079] By integrating the above system, the uniformity of cylinder operation of the diesel engine is significantly improved during operation, thereby achieving the beneficial effects described in Example 1: thermal efficiency is increased by 1% to 1.5%, fuel consumption is reduced by 2% to 3%, particulate matter and nitrogen oxide emissions are reduced by 10% to 15%, inter-cylinder combustion pressure deviation is less than 3 bar, and vibration and noise levels are significantly reduced.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for controlling inter-cylinder combustion deviation in a diesel engine, characterized in that, The method includes: A mirror-symmetric intake system is constructed, and computational fluid dynamics simulation is performed on the intake system to optimize it so that the intake volume deviation of each cylinder of the diesel engine is less than a first preset threshold. Based on the optimized intake system, the uniformity of exhaust gas recirculation distribution is simulated to evaluate the difference in quantity and quality of exhaust gas recirculation gas that can be obtained between cylinders, and to determine whether the distribution difference is less than a second preset threshold. If the distribution difference is not less than the second preset threshold, then adjust the arrangement position parameters of the EGR pipeline in the intake system until the distribution difference is less than the second preset threshold to obtain an exhaust gas optimized intake system. Based on the exhaust gas optimization intake system, the manufacturing and assembly tolerances of one or more key components, such as the control connecting rod, crankshaft, and cylinder bore, are modified to control the compression ratio of each cylinder within the target range. Based on the compression ratio of each cylinder within the target range, calculate the theoretical injection quantity of each cylinder, and select the median flow nozzle based on the theoretical injection quantity to perform injection quantity calibration, ensuring that the injection quantity deviation of each cylinder injector under the same injection pressure is less than the third preset threshold. By coordinating all the above steps, combustion deviations between cylinders of the diesel engine are reduced.

2. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 1, characterized in that, The constructed mirror-symmetrical intake system includes: an intake manifold and multiple mirror-symmetrical intake manifolds. The intake manifold is configured as the central intake layout of the intake system so that the intake airflow directions of the two intake manifolds symmetrical to the intake manifold are completely symmetrical.

3. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 2, characterized in that, The computational fluid dynamics simulation optimization of the intake system includes: steady-state flow resistance simulation and transient intake process simulation; the first preset threshold is 2%-3%.

4. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 2, characterized in that, The optimization of the intake system also includes: adopting a gradient cross-section design at the connection between the intake manifold and the intake main pipe, and / or adding a length compensation section for the intake manifold that flows to the direction furthest from the intake main pipe.

5. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 1, characterized in that, The adjustment of the EGR pipe position parameters includes: adjusting at least one of the following: the EGR pipe inlet direction, the insertion depth into the intake manifold, and the angle. The second preset threshold is 4%-6%.

6. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 1, characterized in that, The control of manufacturing and assembly tolerances includes: The length tolerance of each cylinder connecting rod is controlled within ±0.025mm; The cylindricity tolerance of the crankshaft journal is controlled within 5μm, and the surface roughness Ra≤0.15μm; The roundness tolerance of the cylinder bore is controlled within 3μm, and the cylindricity tolerance is controlled within 5μm.

7. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 1, characterized in that, It also includes verifying the consistency of compression ratio by measuring the piston protrusion height of each cylinder, ensuring that the difference in compression ratio between cylinders is within ±0.

05.

8. The method for controlling inter-cylinder combustion deviation in a diesel engine according to claim 1, characterized in that, The fuel injection quantity calibration also includes: Control the installation height of each cylinder injector so that the distance deviation between the nozzle end face and the top surface of the combustion chamber is within ±0.5mm; Control the injection angle of each cylinder's injector to be consistent; The flow coefficient of the median flow nozzle is the average of the flow coefficients of each cylinder injector; The third preset threshold is 0.5-1.5%.

9. A control system for implementing the method of any one of claims 1 to 8 regarding inter-cylinder combustion deviation in a diesel engine, characterized in that, include: A construction module is used to construct a mirror-symmetric intake system and perform computational fluid dynamics simulation optimization on the intake system so that the intake volume deviation of each cylinder of the diesel engine is less than a first preset threshold. The evaluation module is used to simulate the uniformity of exhaust gas recirculation gas distribution based on the optimized intake system, evaluate the distribution difference in quantity and quality of exhaust gas recirculation gas that can be obtained between cylinders, and determine whether the distribution difference is less than a second preset threshold. An adjustment module is used to adjust the arrangement parameters of the EGR pipeline in the intake system if the distribution difference is not less than the second preset threshold, until the distribution difference is less than the second preset threshold, thereby obtaining an exhaust gas optimized intake system. The control module is used to optimize the intake system based on the exhaust gas and modify the manufacturing and assembly tolerances of one or more key components such as the connecting rod, crankshaft, and cylinder bore in the cylinder block, so that the compression ratio of each cylinder is controlled within the target value range. The calibration module is used to calculate the theoretical fuel injection quantity of each cylinder based on the compression ratio controlled within the target value range, and select the median flow nozzle based on the theoretical fuel injection quantity to perform fuel injection quantity calibration, so as to ensure that the fuel injection quantity deviation of each cylinder injector under the same injection pressure is less than the third preset threshold. The reduction module is used to reduce combustion deviations between cylinders of a diesel engine by coordinating all the above steps.

10. A diesel engine, characterized in that, Includes the system as described in claim 9.

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