Modelica-based multi-source model unified construction method for diesel engine system

Abstract

The invention provides a diesel engine system multi-source model unified construction method based on Modelica, and belongs to the technical field of diesel engine system modeling simulation, and the method comprises the following steps: firstly, carrying out Modelica-based standardized interface design on eight subsystems such as a combustion subsystem, an intake and exhaust pressurization subsystem and a gear transmission subsystem; then, performing interface design, physical equation packaging and connection relation definition on components in each subsystem to form an independent and reusable Modelica subsystem model; and finally, according to the physical coupling relationship among subsystems, all subsystem models are integrated into a unified Modelica model of the whole system of the diesel engine through a standardized interface. Through modularization packaging and interface standardization, the integration problem of multi-source and cross-physical-domain models on a unified platform is solved, coupling of subsystems based on the real physical principle is achieved, the construction efficiency, simulation precision and consistency of the whole system model are remarkably improved, and the system performance is improved. The method can be directly used for engine performance optimization, fault simulation and control strategy verification.

Description

Technical Field

[0001] This invention relates to the field of diesel engine system modeling and simulation technology, and in particular to a unified construction method for multi-source models of diesel engine systems based on Modelica. Background Technology

[0002] Diesel engines are complex coupled systems composed of eight cross-physical domain subsystems, including combustion, intake and exhaust turbocharging, and gear transmission. Performance optimization, fault diagnosis, and control system development rely on the joint simulation of the entire system. However, in existing technologies, the simulation models of each subsystem are typically distributed across different specialized software. For example, the combustion subsystem uses software such as Chemkin and CONVERGE, focusing on in-cylinder combustion reactions; the intake and exhaust turbocharging subsystem uses software such as GT-Power and FLOWMASTER, focusing on fluid flow and turbocharging characteristics; the gear transmission subsystem uses software such as ADAMS and ANSYS, emphasizing mechanical dynamics and transmission efficiency; the control subsystem uses MATLAB / Simulink software to simulate ECU control logic; and the fuel supply, lubrication, and cooling subsystem uses Amesim software to realize fuel supply characteristics.

[0003] Because different subsystems are constructed and simulated using different professional software, there are many defects. For example, the model formats are heterogeneous: the model file formats of different software are incompatible (such as *.gpdx for GT-Power and *.adm for ADAMS), making direct cross-software calls impossible; the interface standards are not unified: the input / output interfaces of each subsystem model (such as the unit of fuel flow and the transmission method of torque) are defined differently, and cross-subsystem interaction requires manual writing of conversion code, which is prone to introducing errors; physical coupling is missing: it is difficult to reproduce the real physical coupling between subsystems during manual integration (such as the force of combustion pressure on the moving mechanism and the influence of intake and exhaust flow on combustion), causing the simulation results of the diesel engine system to deviate from the actual operating conditions; and the modeling efficiency is low: after each adjustment of a subsystem model, all related interfaces need to be manually adapted again, and the modeling cycle of the entire system can take several weeks or even months.

[0004] The multiphysics unified modeling language Modelica and its simulation platforms (such as MWORKS) provide a technological foundation for solving the above problems. However, there is still a lack of a complete, efficient and verifiable method for systematically and faithfully converting and integrating multi-source diesel engine models scattered across various professional software with different description methods into a unified, modular Modelica full-system model. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art, and proposes a unified construction method for multi-source models of diesel engine systems based on Modelica. This overcomes the shortcomings of existing technologies, such as difficulties in integration, low coupling accuracy, and poor modeling efficiency caused by the dispersed and heterogeneous nature of diesel engine subsystem models.

[0006] In a first aspect, embodiments of the present invention provide a unified construction method for multi-source models of diesel engine systems based on Modelica, including: Step S1: Based on the Modelica language, design the component interfaces for each subsystem of the diesel engine. Step S2: Based on the Modelica language, design and encapsulate the interfaces of the components within each subsystem to form an independent subsystem model; Step S3: Based on the Modelica language and the physical principle formulas corresponding to the components, encapsulate the physical equations of each component within the subsystem, so that the component interface is coupled with the physical equations. Step S4: Based on the interface relationships of each subsystem defined in step S1, connect and integrate the various subsystem models constructed in steps S2 and S3 to construct a unified Modelica model for the entire diesel engine system. Step S5: Verify and optimize the Modelica model by comparing the simulation results of the system with those of professional software to verify the consistency of the model, and optimize the coupling accuracy of the model by adjusting the component interface parameters.

[0007] Furthermore, in step S1, the subsystems of the diesel engine include a combustion subsystem, an intake and exhaust turbocharging subsystem, a gear transmission subsystem, a control subsystem, a fuel supply subsystem, a lubrication and cooling subsystem, an energy subsystem, and a motion mechanism subsystem.

[0008] Furthermore, in step S1, the component interface design of each subsystem is specifically as follows: The combustion subsystem is designed with signal interfaces, mechanical interfaces, and gas interfaces; The intake and exhaust booster subsystem is designed with both gas and fluid interfaces; The gear transmission subsystem is equipped with both mechanical and signal interfaces; The control subsystem is designed with signal interfaces; The fuel supply system is designed with both signal and fluid interfaces; The lubrication and cooling subsystem is designed with both signal and fluid interfaces; The energy subsystem is designed with mechanical interfaces; The motion mechanism subsystem is designed with both signal and mechanical interfaces.

[0009] Furthermore, in step S2, the internal components of the combustion subsystem include multiple single-cylinder component models, each of which includes an intake pipe, an intake valve, a cylinder, an exhaust valve, and an exhaust pipe assembly.

[0010] Furthermore, in step S2, the internal components of the intake and exhaust booster subsystem include: two low-pressure compressors, two low-pressure turbines, one high-pressure compressor, one high-pressure turbine, an air source, an intake pipe, an exhaust pipe, an interstage intercooler, a high-pressure stage intercooler, and a rotor assembly. The internal components of the gear transmission subsystem include: crankshaft connecting gear, shaft-driven low-temperature water pump gear, shaft-driven high-temperature water pump gear, shaft-driven low-pressure oil pump gear, and shaft-driven high-pressure oil pump gear. The internal components of the control subsystem include an ECU controller and an ECU controller assembly; The internal components of the fuel supply system include: fuel source, low-pressure fuel pump, high-pressure fuel pump, filter, fuel distributor, fuel rail and fuel injectors; The internal components of the lubrication and cooling subsystem include: a low-temperature water pump, a high-temperature water pump, an intercooler, a high-temperature radiator, a low-temperature radiator, an oil cooler, and a temperature control valve. The internal components of the energy subsystem include: transformer, frequency converter, motor, DC-DC converter and battery; The internal components of the motion mechanism subsystem include a crankshaft and a connecting rod.

[0011] Furthermore, in step S2, the encapsulation of the interface connection of the internal components of the subsystem specifically includes: Inside the combustion subsystem, multiple single-cylinder component models are connected through gas interfaces and signal interfaces to form a multi-cylinder structure; within each single cylinder, the intake pipe, intake valve, cylinder, exhaust valve, and exhaust pipe are connected sequentially through gas interfaces, and the intake valve and exhaust valve are connected through signal interfaces. Inside the intake and exhaust supercharging subsystem, the air source, two low-pressure compressors, pipelines, interstage intercooler, high-pressure compressor, high-pressure stage intercooler, and intake pipeline are sequentially connected through gas interfaces to form the intake supercharging section; the air source, two low-pressure turbines, high-pressure turbine, and exhaust pipeline are sequentially connected through gas interfaces to form the exhaust section; the intake and exhaust sections are connected to the coaxial rotor assembly through signal interfaces; the intake and exhaust pipelines are respectively connected to the combustion subsystem through corresponding gas interfaces. Inside the gear transmission subsystem, the crankshaft connecting gear, the shaft-driven low-temperature water pump gear, the shaft-driven high-temperature water pump gear, the shaft-driven low-pressure oil pump gear, and the shaft-driven high-pressure oil pump gear are connected sequentially through mechanical interfaces; and the crankshaft connecting gear, the shaft-driven low-temperature water pump gear, the shaft-driven high-temperature water pump gear, the shaft-driven low-pressure oil pump gear, and the shaft-driven high-pressure oil pump gear are all equipped with mechanical interfaces and signal interfaces. Inside the fuel supply system, the fuel source, low-pressure fuel pump, filter, high-pressure fuel pump, fuel distributor, fuel rail, and fuel injector are connected in sequence through fluid interfaces. Inside the lubrication and cooling subsystem, the cryogenic water pump, oil cooler, temperature control valve, and cryogenic radiator are connected through fluid interfaces to form a cryogenic circuit; the high-temperature water pump, intercooler, temperature control valve, and high-temperature radiator are connected through fluid interfaces to form a high-temperature circuit; the gas source, high-temperature radiator, and cryogenic radiator are connected through gas interfaces to form a circuit; among them, the cryogenic water pump and the high-pressure water pump are respectively connected to the exhaust booster subsystem through their corresponding fluid interfaces.

[0012] Furthermore, in step S3, encapsulating the physical equations of the component specifically means: based on the physical characteristics of the component, establishing a mathematical model based on the principles of mass conservation, energy conservation, and performance characteristics, and coupling the mathematical model with the input / output interface of the component, so that the component can perform the corresponding physical function through the parameters passed by the interface.

[0013] Furthermore, in step S4, constructing a unified Modelica model for the entire diesel engine system specifically includes the following connection relationships: The control subsystem is connected to the fuel supply subsystem via a signal interface. Specifically, the ECU controller of the control subsystem controls the opening and closing status of each fuel injector in the fuel supply subsystem. The gear transmission subsystem is connected to the oil supply subsystem and the lubrication and cooling subsystem via signal interfaces, and to the motion mechanism subsystem via mechanical interfaces. The intake and exhaust turbocharging subsystem is connected to the combustion subsystem via a gas interface; The fuel supply system is connected to the combustion system via a fluid interface. Specifically, each fuel injector in the fuel supply system is connected to the combustion system via a fluid interface. The lubrication and cooling subsystem is connected to the intake and exhaust booster subsystem via a fluid interface; The crankshaft of the motion mechanism subsystem is connected to the combustion subsystem via mechanical and signal interfaces. The motion mechanism subsystem is connected to the energy subsystem via a mechanical interface.

[0014] Furthermore, in step S5, the verification and optimization specifically includes: running each subsystem in the full system model respectively, comparing its simulation results with the simulation results of the corresponding subsystem model constructed by the original professional software, and verifying the consistency of the model.

[0015] Furthermore, in step S5, the coupling accuracy of the optimized model specifically refers to: based on the comparison results between the simulation data of the whole system model and the target data, adjusting the interface parameters of the Modelica subsystem component model so that the simulation results of the whole system model have a consistency with the reference results obtained by professional simulation software above a set threshold.

[0016] The technical advantages of the Modelica-based unified construction method for multi-source models of diesel engine systems disclosed in this invention are as follows: By using a unified Modelica platform and standardized interface definitions, the difficulties in integrating multi-source models caused by heterogeneous model formats and inconsistent interfaces are completely resolved. Component modeling and system assembly based on physical equations ensure that the energy, mass, and momentum transfer between subsystems strictly follows physical laws. Information exchange and control between subsystems are achieved through signal transmission to realize preset functional logic, significantly improving the accuracy and reliability of system-level simulation. The component-based modeling method makes the model easy to reuse, modify, and extend. Once the subsystem model is completed, the integration and adjustment of the entire system become fast and convenient, greatly shortening the development cycle. The constructed high-fidelity unified model can be directly used for diesel engine performance prediction and optimization, fault injection and simulation, and hardware-in-the-loop (HIL) testing and verification of control systems (such as ECUs), possessing significant engineering practical value. Attached Figure Description

[0017] Figure 1 A flowchart illustrating a method for unified construction of multi-source models of a diesel engine system based on Modelica, provided in an embodiment of the present invention; Figure 2 A schematic diagram of the connection relationship of the intake and exhaust turbocharging subsystems in a unified construction method for a multi-source model of a diesel engine system based on Modelica, provided by the present invention; Figure 3 A schematic diagram of the gear transmission subsystem connection relationship in a unified construction method for multi-source models of a diesel engine system based on Modelica, provided by the present invention; Figure 4 A schematic diagram of the control subsystem connection relationship for a unified construction method of multi-source models of diesel engine systems based on Modelica provided by the present invention; Figure 5 A schematic diagram of the fuel supply subsystem connection relationship in a unified construction method for a multi-source model of a diesel engine system based on Modelica provided by the present invention; Figure 6 A schematic diagram of the connection relationship of the lubrication and cooling subsystem in a unified construction method for a multi-source model of a diesel engine system based on Modelica, provided by the present invention; Figure 7 A schematic diagram of the energy subsystem connection relationship of a unified construction method for multi-source models of diesel engine systems based on Modelica provided by the present invention; Figure 8A schematic diagram of the connection relationship of the motion mechanism subsystems in a unified construction method for multi-source models of a diesel engine system based on Modelica, provided by the present invention; Figure 9 A schematic diagram of the connection relationship of a diesel engine system based on Modelica for a unified construction method of multi-source models of diesel engine systems provided by the present invention; Figure 10 A schematic diagram comparing the simulation and actual measurement results of the fuel injection quantity of the fuel supply subsystem provided by the present invention; Figure 11 A schematic diagram comparing the simulation and actual measurement results of the high-temperature circuit return water temperature of the cooling subsystem provided by this invention; Figure 12 This is a schematic diagram comparing the simulation and actual measurement results of the crankshaft speed of the motion mechanism subsystem provided by the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0019] A unified construction method for multi-source models of diesel engine systems based on Modelica, referencing Figures 1 to 12 As shown, the specific steps include: Step S1: Based on the Modelica language, design the component interfaces for each subsystem of the diesel engine. These subsystems include the combustion subsystem, intake and exhaust turbocharging subsystem, gear transmission subsystem, control subsystem, fuel supply subsystem, lubrication and cooling subsystem, energy subsystem, and motion mechanism subsystem. The interface design defines standardized "ports" for each subsystem to interact with external systems. For example, the combustion subsystem has a signal interface (for receiving control commands), a mechanical interface (for outputting torque), and a gas interface (for intake and exhaust); the intake and exhaust turbocharging subsystem has a gas interface (connecting to the intake and exhaust ports) and a fluid interface (connecting to the cooling system).

[0020] By pre-defining a unified, physical type-based interface standard, a communication foundation was established for the subsequent integration of heterogeneous models, thus solving the interface mismatch problem at its source.

[0021] The specific definitions are as follows: Combustion subsystem: As the core power source, it needs to exchange control signals, mechanical torque, and working gas with the outside world. Therefore, it is designed with a signal interface (receiving control commands such as fuel injection and ignition), a mechanical interface (outputting crankshaft torque), and a gas interface (connecting the intake and exhaust pipes).

[0022] Intake and exhaust turbocharging subsystem: handles airflow and pressurization, and exchanges heat with the cooling system. It includes a gas interface (connecting to the air source and combustion chamber) and a fluid interface (connecting to the coolant circuit).

[0023] Gear transmission subsystem: transmits and distributes power. Designs a signal interface (for outputting speed signals to control accessories).

[0024] Control Subsystem (ECU): Generates control logic. Designs signal interfaces (input sensor signals, output actuator commands).

[0025] Fuel supply subsystem: delivers and injects fuel. It includes a signal interface (receiving control signals from the fuel pump and injectors) and a fluid interface (delivering fuel). The fuel pump receives a speed signal, which changes the pump speed accordingly.

[0026] Lubrication and cooling subsystem: manages the circulation of coolant and engine oil. It includes signal interfaces (for receiving water pump control signals) and fluid interfaces (for connecting various components requiring cooling).

[0027] Energy subsystems (such as generators and batteries): manage electrical power and are designed with only mechanical structures.

[0028] The motion mechanism subsystem converts combustion pressure into rotational motion. It includes a signal interface (outputting crankshaft speed or torque signals) and a mechanical interface (inputting cylinder force and outputting rotational power).

[0029] By defining a unified "interaction language" (interface types and standards) for eight subsystem models from different professional backgrounds, it is like defining a common communication protocol for people from different countries, laying a solid foundation for subsequent "plug-and-play" integration on the Modelica platform and directly overcoming the core defect of "inconsistent interface standards" in the background technology.

[0030] Step S2: Based on the Modelica language, design and encapsulate the interfaces of the components within each subsystem to form an independent Modelica model for the subsystem.

[0031] This step involves a detailed decomposition of each subsystem. For example, the combustion subsystem consists of multiple single-cylinder component models, each of which contains sub-components such as intake pipes, intake valves, cylinders, exhaust valves, and exhaust pipes. The interfaces of all internal components (such as gas interfaces, signal interfaces, mechanical interfaces, fluid interfaces, and electrical interfaces) and their connection topologies are defined in detail. For instance, within the combustion subsystem, multiple single cylinders are connected in parallel via gas interfaces, and the components within each single cylinder are connected sequentially according to the airflow direction. The technical advantage of this step is that it achieves componentization and modularization of the subsystem model, making each subsystem a reusable module with a clear internal structure and well-defined external interfaces, greatly improving the flexibility and maintainability of the modeling process.

[0032] Among them, combined Figure 2 As shown, the key subsystems are as follows: 1. Combustion Subsystem: Internally composed of multiple single-cylinder component models. Each single cylinder is a reusable submodule, containing five sub-components: intake manifold, intake valve, cylinder, exhaust valve, and exhaust manifold. Its internal encapsulation logic is as follows: within a single cylinder, the five sub-components are connected in series via gas interfaces according to the working fluid flow direction. The intake and exhaust valves also need to be connected to signal interfaces to receive opening and closing commands. The intake and exhaust manifolds of multiple single cylinders are connected in parallel via gas interfaces to form a multi-cylinder model. Their mechanical interfaces aggregate and output the total cylinder pressure, which is then connected to the motion subsystem to drive the crankshaft rotation. Changes in crankshaft angle in the motion subsystem are transmitted to the fuel subsystem via signal interfaces, thereby controlling the opening and closing states of the intake and exhaust valves.

[0033] 2. Intake and Exhaust Turbocharging Subsystem: The internal components are complex. Its encapsulation logic is as follows: On the intake side, air flows sequentially from the air source through two low-pressure compressors, an interstage intercooler, a high-pressure compressor, and a high-pressure stage intercooler, finally exiting through the intake duct. All components are connected via gas interfaces. On the exhaust side, exhaust gas flows sequentially through two low-pressure turbines and one high-pressure turbine, with all components connected via gas interfaces. The compressors and turbines on both the intake and exhaust sides achieve mechanical and aerodynamic energy coupling through rotor assemblies (connected via signal interfaces). The intake and exhaust ducts are connected to the combustion subsystem via corresponding gas interfaces.

[0034] 3. Fuel Supply System: The internal components include the complete path from the fuel source to the fuel injector. Its encapsulation logic is as follows: fuel starts from the fuel source, passes through the low-pressure fuel pump (controlled by a signal interface), filter, high-pressure fuel pump (controlled by a signal interface), fuel distributor, fuel rail, and finally reaches the fuel injector (controlled by a signal interface). All fluid circuit components are connected in series through fluid interfaces.

[0035] 4. Lubrication and Cooling Subsystem: This system is divided into two circuits: a high-temperature circuit and a low-temperature circuit. The encapsulation logic is as follows: The low-temperature circuit (cooling the intercooler, etc.) is driven by a low-temperature water pump (controlled by a signal interface), which flows the coolant through the oil cooler, thermostatic valve, and low-temperature radiator, forming a closed loop through the fluid interface. The high-temperature circuit (cooling the engine block) is driven by a high-temperature water pump, flowing through the intercooler (on the other side), thermostatic valve, and high-temperature radiator. The heat carried away by the coolant from the engine block can be equivalent to the heat absorbed by the intercooler, thus raising the coolant temperature. The two circuits are connected or isolated through the fluid interface of the thermostatic valve. The intercooler, through its gas and fluid interfaces, serves as a gas-liquid heat exchange hub.

[0036] 5. Based on Figure 3 It is known that the crankshaft connecting gear, shaft-driven low-temperature water pump gear, shaft-driven high-temperature water pump gear, shaft-driven low-pressure oil pump gear, and shaft-driven high-pressure oil pump gear, which are internal components of the gear transmission subsystem, have mechanical interfaces and signal interfaces. Among them, the crankshaft connecting gear is connected to the shaft-driven low-temperature water pump gear, shaft-driven high-temperature water pump gear, shaft-driven low-pressure oil pump gear, and shaft-driven high-pressure oil pump gear in sequence through mechanical interfaces. A sensor is connected at the mechanical port of the shaft-driven pump gear to convert the mechanical interface into a signal interface, thereby forming the entire transmission subsystem.

[0037] 6. Based on Figure 4 As can be seen, the internal components of the control subsystem, the ECU controller and the ECU controller component, have signal interfaces. These signal interfaces are directly connected to form the control subsystem, which is mainly used to control the opening and closing of the fuel injectors.

[0038] 7. Based on Figure 5 It can be seen that the internal components of the fuel supply system, such as the fuel source, filter, fuel distributor, and high-pressure fuel rail, have fluid interfaces, while the low-pressure fuel pump, high-pressure fuel pump, and fuel injector have both fluid and signal interfaces. The fuel source, low-pressure fuel pump, filter, high-pressure fuel pump, fuel distributor, fuel rail, and fuel injector are connected sequentially through the fluid interfaces. The low-pressure and high-pressure fuel pumps control the pump speed through the signal interfaces. The external signal is provided by the gear transmission subsystem. At the same time, the signal interface provided by the fuel injector further forms the encapsulation of the entire fuel supply system.

[0039] 8. Based on Figure 6It is known that the internal components of the lubrication and cooling subsystem include a cryogenic water pump and a high-temperature water pump with signal and fluid interfaces; an intercooler, an oil cooler, and a temperature control valve with fluid interfaces; and a high-temperature radiator and a cryogenic radiator with fluid and gas interfaces. The cryogenic water pump, pipes, oil cooler, temperature control valve, and cryogenic radiator are sequentially connected via fluid interfaces to form a cryogenic loop. The high-temperature water pump, intercooler, temperature control valve, and high-temperature radiator are connected via fluid interfaces to form a high-temperature loop. The high-temperature loop and the cryogenic loop are connected via gas interfaces. The gas source, high-temperature radiator, and cryogenic radiator are connected via gas interfaces to form a loop. The cryogenic water pump and high-pressure water pump are connected to the exhaust booster subsystem via their respective fluid interfaces. The low-pressure and high-pressure water pumps control their speed via signal interfaces, with external signals provided by the gear transmission subsystem.

[0040] 9. Based on Figure 7 It can be seen that the transformer, frequency converter, DC-DC converter and battery in the internal components of the energy subsystem have electrical interfaces, and the motor has mechanical interfaces and electrical interfaces. The transformer, frequency converter, DC-DC converter and battery are connected in sequence through electrical interfaces to form the electrical subsystem. The mechanical interface left by the motor is mainly used to connect with the motion structure subsystem.

[0041] 10. Based on Figure 8 It can be seen that the crank and connecting rod in the motion mechanism subsystem have mechanical interfaces and signal interfaces; the crank and multiple connecting rods are connected in sequence to form the motion mechanism subsystem.

[0042] By decomposing components and defining internal interfaces, each complex engineering subsystem is transformed into a well-structured and hierarchical Modelica module library. This "divide and conquer" strategy allows modeling to be carried out in parallel, with each component being developed, tested, and reused independently, significantly improving modeling efficiency (overcoming the shortcomings of "low modeling efficiency") and providing a clear framework for the physical implementation of step S3.

[0043] Step S3: Based on the Modelica language and the corresponding physical principle formulas of the components, encapsulate the physical equations of each component within the subsystem, so that the component interface is coupled with the physical equations.

[0044] For each physical component (such as a compressor, cylinder, and oil pump), mathematical equations describing its behavior (such as mass conservation equations, energy conservation equations, and performance characteristic equations) are written using the Modelica language, based on its physical nature (thermodynamics, fluid mechanics, etc.). The key is to bind these equations to the component interface variables (such as inlet pressure, outlet flow rate, rotational speed, and torque) defined in step S2. This ensures that each Modelica component accurately reflects the dynamic behavior of its physical entity, providing a high-fidelity basic unit for the whole system simulation and is the core of achieving precise physical coupling.

[0045] Taking the compressor component in the intake and exhaust supercharging subsystem as an example: In the Modelica class definition, in addition to defining its gas inlet and gas outlet interfaces, its speed and torque signal interfaces also need to be defined. In the equations section, the following physical equations need to be encapsulated: Mass conservation equation: der(m) = port_a.m_flow + port_b.m_flow; where m is the mass of the working fluid in the compressor, and port_a.m_flow and port_b.m_flow are the inlet and outlet mass flow rates transmitted through the interface.

[0046] Energy conservation equation: der(U) = port_a.H_flow + port_b.H_flow + tau * omega; where U is internal energy, H_flow is the enthalpy flow transmitted through the interface, tau and omega are the torque and angular velocity transmitted through the interface, and the tau * omega term represents the mechanical work input to the gas.

[0047] Performance characteristic equations (or MAP interpolation): pi = f(omega, m_flow); eta = g(omega, m_flow); where pi is the pressure ratio and eta is the efficiency. These characteristic equations, coupled with omega and m_flow transmitted through the interface, calculate the pressure ratio and efficiency under the current operating conditions in real time, thereby determining the outlet pressure port_b.p and temperature.

[0048] By visualizing abstract physical laws (conservation of mass, energy, and momentum) and concrete engineering data (characteristic maps) through the Modelica language and binding them to standardized interfaces, each component is no longer a "black box" but a "white box" model with clear physical meaning that can dynamically calculate based on input conditions. This is the fundamental guarantee for achieving "real physical coupling" rather than "data exchange" between subsystems.

[0049] Step S4: Based on the interface relationships of each subsystem defined in Step S1, connect and integrate the various subsystem models constructed in Steps S2 and S3 to construct a unified Modelica model for the entire diesel engine system.

[0050] Based on the actual physical connections of the diesel engine, the models of each subsystem are "assembled" using standardized interfaces. Specific connections include: the control subsystem controls the fuel supply subsystem via a signal interface; the gear transmission subsystem drives the oil pump of the fuel supply subsystem and the water pump of the lubrication and cooling subsystem via a signal interface; the intake and exhaust turbocharging subsystem provides pressurized air to the combustion subsystem and exhausts exhaust gases via a gas interface; the fuel supply subsystem supplies fuel to the combustion subsystem via a fluid interface; the lubrication and cooling subsystem cools the intercooler in the intake and exhaust turbocharging subsystem via a fluid interface; and the motion mechanism subsystem interacts with the combustion subsystem through mechanical and signal interfaces, outputting power to the energy subsystem. This achieves seamless integration of multi-source, cross-physical domain models on a unified platform (such as MWORKS), constructing an integrated digital prototype capable of fully simulating the operation of a diesel engine under all operating conditions.

[0051] like Figure 9 As shown, based on the actual physical topology of the diesel engine, the eight subsystem models are connected like building blocks: The signal interface of the control subsystem leads to the signal interface of the fuel supply subsystem (for fuel injection control). Specifically, the ECU controller of the control subsystem controls the opening and closing status of each fuel injector in the fuel supply subsystem.

[0052] The signal interface of the gear transmission subsystem connects to the signal interface of the oil supply subsystem (providing the oil pump speed reference). It also connects to the motion mechanism subsystem via a mechanical interface.

[0053] Signal interface of gear transmission subsystem → Signal interface of lubrication and cooling subsystem (provides water pump speed reference).

[0054] Gas interface of intake and exhaust supercharging subsystem The gas interface of the combustion subsystem (provides pressurized air and receives exhaust gas).

[0055] The fluid interface of the fuel supply system leads to the single-cylinder assembly (fuel injection) of the combustion system. Specifically, each fuel injector in the fuel supply system is connected to the combustion system through the fluid interface.

[0056] Fluid interface of the lubrication and cooling subsystem → interstage intercooler and high-pressure stage intercooler of the intake and exhaust boosting subsystem (cooling boosted air).

[0057] The crankshaft of the combustion subsystem is connected via mechanical and signal interfaces (cylinder pressure, crankshaft position). The motion mechanism subsystem (converts pressure into torque and speed signals).

[0058] The motion mechanism subsystem connects to the motor of the energy subsystem via a mechanical interface (outputting surplus power to generate electricity).

[0059] Ultimately, a unified platform integration of multi-source models was achieved. All subsystems run in the same Modelica simulation environment, and the solver can simultaneously solve the entire system of multiphysics coupled differential-algebraic equations (DAEs). This completely solves the problems of "heterogeneous model formats" and "lack of physical coupling," forming a virtual diesel engine capable of high-fidelity, real-time interaction.

[0060] Step S5: Verify and optimize the unified Modelica model of the entire diesel engine system. First, perform consistency verification: run a separate subsystem from the full system model (e.g., the intake and exhaust turbocharging subsystem), and compare its simulation results (e.g., compressor outlet pressure, flow rate) with the simulation results of the same subsystem built using original professional software (e.g., GT-Power) under the same boundary conditions to verify the accuracy of the converted Modelica subsystem model. Then, optimize coupling accuracy: run the complete full system model, compare the simulation data with target data or the combined simulation results of professional software, and optimize the coupling effect between subsystems by adjusting the parameters of key component interfaces (e.g., flow coefficient, efficiency correction coefficient, etc.) to achieve the required accuracy for the entire system simulation results (e.g., consistency exceeding 95%). Through a scientific V&V (verification and validation) process, the accuracy of the original subsystems is maintained while achieving high-fidelity coupling between systems, ensuring the credibility of the simulation results.

[0061] Specifically, it includes: (1) Subsystem-level verification: Taking the intake and exhaust supercharging subsystem as an example. Under the same boundary conditions (ambient pressure and temperature, compressor speed, turbine back pressure), the original model constructed by GT-Power and the Modelica model constructed by the method of this invention were run respectively. Key performance parameters were compared, such as Figures 10 to 12 As shown, the Modelica simulation values ​​for the fuel injection quantity of the fuel supply subsystem, the return water temperature of the high-temperature circuit of the cooling subsystem, and the crankshaft speed of the motion mechanism subsystem are highly consistent with the reference values ​​of software such as GT-Power, with an error within 5%. This verifies the equivalent substitutability of a single Modelica subsystem model for the original professional software model.

[0062] (2) System-level optimization: After completing the subsystem verification, run the complete full-system model. Compare the full-system simulation output (such as power, fuel consumption, emissions) with bench test data or other reliable co-simulation results. If a deviation is found, trace it back to the coupling interface of the relevant subsystem. For example, if the low-speed torque is found to be low, check and adjust the model parameters regarding friction loss in the mechanical interface transmitted from the combustion subsystem to the motion mechanism subsystem; or adjust the flow coefficient of the gas interface between the intake and exhaust subsystems and the combustion subsystem. Through multiple iterations, ensure that the simulation accuracy of the full-system model meets engineering requirements (such as consistency of key indicators > 95%). The technical effect of this step is that, through a rigorous V&V process, it ensures that the constructed unified model not only inherits the accuracy of each subsystem, but also meets the reliability requirements for engineering applications at the system coupling level, so that the model can truly be used to guide product development and optimization.

[0063] This invention provides a complete methodology from interface standardization, component-based modeling, physical equation encapsulation, system integration to final verification and optimization. It effectively breaks down the technical barriers of multi-domain diesel engine simulation, and the unified and intuitive model it constructs provides a powerful tool for the digital design, testing, and maintenance of engines.

[0064] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. A unified construction method for multi-source models of diesel engine systems based on Modelica, characterized in that, include: Step S1: Based on the Modelica language, design the component interfaces for each subsystem of the diesel engine. Step S2: Based on the Modelica language, design and encapsulate the interfaces of the components within each subsystem to form an independent subsystem model; Step S3: Based on the Modelica language and the physical principle formulas corresponding to the components, encapsulate the physical equations of each component within the subsystem, so that the component interface is coupled with the physical equations. Step S4: Based on the interface relationships of each subsystem defined in step S1, connect and integrate the various subsystem models constructed in steps S2 and S3 to construct a unified Modelica model for the entire diesel engine system. Step S5: Verify and optimize the Modelica model by comparing the simulation results of the system with those of professional software to verify the consistency of the model, and optimize the coupling accuracy of the model by adjusting the component interface parameters.

2. The method according to claim 1, characterized in that, In step S1, the subsystems of the diesel engine include a combustion subsystem, an intake and exhaust turbocharging subsystem, a gear transmission subsystem, a control subsystem, a fuel supply subsystem, a lubrication and cooling subsystem, an energy subsystem, and a motion mechanism subsystem.

3. The method according to claim 2, characterized in that, In step S1, the component interface design of each subsystem is specifically as follows: The combustion subsystem is designed with signal interfaces, mechanical interfaces, and gas interfaces; The intake and exhaust booster subsystem is designed with both gas and fluid interfaces; The gear transmission subsystem is equipped with both mechanical and signal interfaces; The control subsystem is designed with signal interfaces; The fuel supply system is designed with both signal and fluid interfaces; The lubrication and cooling subsystem is designed with both signal and fluid interfaces; The energy subsystem is designed with mechanical interfaces; The motion mechanism subsystem is designed with both signal and mechanical interfaces.

4. The method according to claim 2, characterized in that, In step S2, the internal components of the combustion subsystem include multiple single-cylinder component models, each of which includes an intake pipe, an intake valve, a cylinder, an exhaust valve, and an exhaust pipe assembly.

5. The method according to claim 2, characterized in that, In step S2, the internal components of the intake and exhaust booster subsystem include: two low-pressure compressors, two low-pressure turbines, one high-pressure compressor, one high-pressure turbine, an air source, an intake pipe, an exhaust pipe, an interstage intercooler, a high-pressure stage intercooler, and a rotor assembly. The internal components of the gear transmission subsystem include: crankshaft connecting gear, shaft-driven low-temperature water pump gear, shaft-driven high-temperature water pump gear, shaft-driven low-pressure oil pump gear, and shaft-driven high-pressure oil pump gear. The internal components of the control subsystem include an ECU controller and an ECU controller assembly; The internal components of the fuel supply system include: fuel source, low-pressure fuel pump, high-pressure fuel pump, filter, fuel distributor, fuel rail and fuel injectors; The internal components of the lubrication and cooling subsystem include: a low-temperature water pump, a high-temperature water pump, an intercooler, a high-temperature radiator, a low-temperature radiator, an oil cooler, and a temperature control valve. The internal components of the energy subsystem include: transformer, frequency converter, motor, DC-DC converter and battery; The internal components of the motion mechanism subsystem include a crankshaft and a connecting rod.

6. The method according to claim 4 or 5, characterized in that, In step S2, the encapsulation of the interface connection of the internal components of the subsystem is specifically as follows: Inside the combustion subsystem, multiple single-cylinder component models are connected through gas interfaces and signal interfaces to form a multi-cylinder structure; within each single cylinder, the intake pipe, intake valve, cylinder, exhaust valve, and exhaust pipe are connected sequentially through gas interfaces, and the intake valve and exhaust valve are connected through signal interfaces. Inside the intake and exhaust supercharging subsystem, the air source, two low-pressure compressors, pipelines, interstage intercooler, high-pressure compressor, high-pressure stage intercooler, and intake pipeline are sequentially connected through gas interfaces to form the intake supercharging section; the air source, two low-pressure turbines, high-pressure turbine, and exhaust pipeline are sequentially connected through gas interfaces to form the exhaust section; the intake and exhaust sections are connected to the coaxial rotor assembly through signal interfaces; the intake and exhaust pipelines are respectively connected to the combustion subsystem through corresponding gas interfaces. Inside the gear transmission subsystem, the crankshaft connecting gear, the shaft-driven low-temperature water pump gear, the shaft-driven high-temperature water pump gear, the shaft-driven low-pressure oil pump gear, and the shaft-driven high-pressure oil pump gear are connected sequentially through mechanical interfaces; and the crankshaft connecting gear, the shaft-driven low-temperature water pump gear, the shaft-driven high-temperature water pump gear, the shaft-driven low-pressure oil pump gear, and the shaft-driven high-pressure oil pump gear are all equipped with mechanical interfaces and signal interfaces. Inside the fuel supply system, the fuel source, low-pressure fuel pump, filter, high-pressure fuel pump, fuel distributor, fuel rail, and fuel injector are connected in sequence through fluid interfaces. Inside the lubrication and cooling subsystem, the cryogenic water pump, oil cooler, temperature control valve, and cryogenic radiator are connected through fluid interfaces to form a cryogenic circuit; the high-temperature water pump, intercooler, temperature control valve, and high-temperature radiator are connected through fluid interfaces to form a high-temperature circuit; the gas source, high-temperature radiator, and cryogenic radiator are connected through gas interfaces to form a circuit; among them, the cryogenic water pump and the high-pressure water pump are respectively connected to the exhaust booster subsystem through their corresponding fluid interfaces.

7. The method according to claim 1, characterized in that, In step S3, encapsulating the physical equations of the component specifically means: based on the physical characteristics of the component, establishing a mathematical model based on the principles of mass conservation, energy conservation, and performance characteristics, and coupling the mathematical model with the input / output interface of the component so that the component can execute the corresponding physical function through the parameters passed through the interface.

8. The method according to claim 1, characterized in that, In step S4, constructing a unified Modelica model for the entire diesel engine system specifically includes the following connection relationships: The control subsystem is connected to the fuel supply subsystem via a signal interface. Specifically, the ECU controller of the control subsystem controls the opening and closing status of each fuel injector in the fuel supply subsystem. The gear transmission subsystem is connected to the oil supply subsystem and the lubrication and cooling subsystem via signal interfaces, and to the motion mechanism subsystem via mechanical interfaces. The intake and exhaust turbocharging subsystem is connected to the combustion subsystem via a gas interface; The fuel supply system is connected to the combustion system via a fluid interface. Specifically, each fuel injector in the fuel supply system is connected to the combustion system via a fluid interface. The lubrication and cooling subsystem is connected to the intake and exhaust booster subsystem via a fluid interface; The crankshaft of the motion mechanism subsystem is connected to the combustion subsystem via mechanical and signal interfaces. The motion mechanism subsystem is connected to the energy subsystem via a mechanical interface.

9. The method according to claim 1, characterized in that, In step S5, the verification and optimization specifically includes: running each subsystem in the full system model respectively, comparing its simulation results with the simulation results of the corresponding subsystem model constructed by the original professional software, and verifying the consistency of the model.

10. The method according to claim 9, characterized in that, In step S5, the coupling accuracy of the optimized model specifically refers to: based on the comparison results between the simulation data of the whole system model and the target data, adjusting the interface parameters of the Modelica subsystem component model so that the simulation results of the whole system model have a consistency with the reference results obtained by professional simulation software above a set threshold.

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