Simulation analysis method for simulating starting process of diesel engine

Abstract

The invention discloses a simulation analysis method for simulating the starting process of a diesel engine, and the method comprises the steps: building a power plant diesel engine one-dimensional performance simulation calculation model (namely a diesel engine one-dimensional starting model) according to the operation environment conditions, structural parameters and control parameters of the power plant diesel engine, and then carrying out the simulation analysis of the starting process of the diesel engine based on the power plant diesel engine one-dimensional performance simulation calculation model; simulating and solving the influence of different parameters on the time required for starting; and finally, carrying out sensitivity analysis on all parameters based on simulation result data, and determining the parameter which has the greatest influence on the time required for starting the diesel engine. The method can determine the main influence factors of the starting process performance of the diesel engine in the power plant, saves the starting test cost, and provides targeted guidance for design improvement.

Description

Technical Field

[0001] This invention relates to diesel engine starting technology, and more specifically to a simulation analysis method for simulating the diesel engine starting process. Background Technology

[0002] In scenarios such as base stations, industrial and mining enterprises, and power grid peak shaving, the core function is to quickly and reliably start up and supply power when the main power grid fails or there is a power shortage. The success and performance of the startup process directly affect the safety and stability of the entire power supply system.

[0003] However, the starting process of a power plant diesel engine is a highly complex and strongly nonlinear transient process, involving the dynamic coupling and interaction of multiple subsystems, including the starter motor, battery, engine body, fuel injection system, and speed control system. Currently, the main challenges in this technological field are as follows:

[0004] In practical applications, especially in low-temperature environments, diesel engines often fail to start or attempt multiple starts due to insufficient starting torque, battery voltage drops, or poor combustion. This can be fatal in emergency power supply scenarios, potentially leading to significant economic losses or even safety accidents. Traditional trial-and-error research and bench testing require the manufacture of numerous physical prototypes and testing under various extreme environments. This process is time-consuming, extremely costly, and struggles to cover all potential failure conditions. Furthermore, among numerous design, environmental, and control parameters, traditional experience makes it difficult to quantify which factors are most critical to starting success, resulting in a lack of targeted improvement measures.

[0005] Therefore, there is an urgent need in this field for a simulation analysis method and supporting virtual device that can comprehensively, accurately and efficiently simulate the entire starting process of a diesel engine in a power plant, in order to overcome the shortcomings of existing technologies and provide a powerful virtual verification platform for the reliability design, control strategy optimization and fault diagnosis of diesel generator sets. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the existing technology and provide a simulation analysis method for simulating the starting process of a diesel engine.

[0007] Technical Solution: This invention provides a simulation analysis method for simulating the starting process of a diesel engine. First, the operating environment conditions, structural parameters, and control parameters of the power plant diesel engine are obtained, and a one-dimensional starting model of the diesel engine is constructed based on these parameters. Then, the one-dimensional starting model is used to perform a one-dimensional simulation calculation of the diesel engine's starting transient process, calculating the impact of different parameters on the starting time required for the diesel engine (i.e., analyzing the impact on the performance indicators of the diesel engine's speed increase). Finally, sensitivity analysis of the simulation results (each parameter) is performed using a combination of Pearson correlation coefficient, Spearman rank correlation coefficient, standardized regression coefficient, and partial correlation coefficient.

[0008] In the one-dimensional simulation calculation of the diesel engine's starting transient process, an electric motor is used for reverse dragging until the diesel engine can autonomously inject fuel and reach the target speed. The one-dimensional starting model of the diesel engine includes the following sub-models:

[0009] Sub-model 1, Combustion Model: This model describes the relationship between the combustion heat release rate and the crankshaft angle, and calculates the in-cylinder pressure and temperature to obtain the engine's indicated power, torque, and power performance parameters.

[0010] Sub-model 2, heat transfer model, is the Woschni instantaneous heat transfer model used to predict the heat transfer rate and heat loss between various components of the diesel engine and the working fluid flowing through it; the heat transfer model includes a core formula describing the convective heat transfer coefficient and a local average gas velocity model used to characterize the motion state of the working fluid in the cylinder.

[0011] Sub-model 3, Fuel Injection Model (the fuel injection model is the fuel injection module with air-fuel ratio pulse in GT-POWER). The fuel injection model is a fuel injection module with air-fuel ratio pulse, which is used to convert the control parameters of the fuel injection system into quantitative information of the in-cylinder mixture, in order to prepare for the combustion calculation of the mixture. In the specific setting of model parameters, if the actual value of the fuel delivery rate cannot be obtained directly from the technical data, it is necessary to make a reasonable estimate by using empirical formulas and the basic operating principle of the engine.

[0012] Sub-model 4, Intake and Exhaust System: This model simulates the flow of gas in the pipeline, including: air filter, compressor, intercooler, intake pipe, throttle valve, exhaust pipe, turbine, and three-way catalytic converter. It solves for the propagation and changes of pressure, temperature, flow rate, and components in the pipeline.

[0013] Sub-model 5, Cylinder Assembly, simulates the operation of the cylinder, including the combustion model and heat transfer model mentioned above, as well as the valve timing model (defining the opening and closing rules of the intake and exhaust valves) and the properties of the gas inside the cylinder (including the composition and physical properties of the working fluid).

[0014] Sub-model 6, Mechanical System: The mechanical system converts the thermodynamic work generated by the gas pressure in the cylinder into usable shaft work and simulates the rotational dynamics of the crankshaft system.

[0015] Furthermore, the diesel engine starting device in the one-dimensional diesel engine starting model includes an engine system, a starter motor, a battery pack, and a meshing mechanism. The meshing mechanism is installed between the starter motor and the diesel engine flywheel of the whole machine, and is used to transmit the torque generated by the starter motor to the diesel engine flywheel. The starter motor is installed between the battery pack and the meshing mechanism, and is used to obtain electrical energy from the battery to generate rotational torque to drive the engine flywheel to rotate.

[0016] The engine system includes engine block components (cylinder block, cylinder head, crankcase, etc.), crankshaft and connecting rod mechanism (piston, connecting rod, crankshaft, etc.), valve train (intake and exhaust valves, camshaft, valve springs, etc.), fuel system (fuel injection pump, injectors, fuel pump, fuel filter, etc.), and turbocharger (compressor, turbine).

[0017] During the one-dimensional simulation calculation, the controller first issues a start command, engages the clutch, and causes the battery pack to drive the starter motor to rotate, thereby dragging the engine. When the engine speed reaches the preset autonomous operation threshold, the controller immediately issues a command to disengage the clutch to cut off power transmission and prevent the engine from dragging the starter motor. Then, air enters through the intake inlet, is filtered by the air filter, and is pressurized by the compressor. The pressurized high-pressure air is distributed through the intake manifold and enters each cylinder through the intake valve. The exhaust gas generated by combustion is discharged from the exhaust valve, collected in the exhaust duct, and drives the turbine. The rotation of the turbine drives the coaxial compressor to work, and finally the exhaust gas is treated by the catalytic converter and discharged into the atmosphere.

[0018] Furthermore, the formula describing the change of combustion heat release rate with crankshaft angle in the combustion model is as follows;

[0019] ;

[0020] In the above formula, Indicates the cumulative mass percentage burned. Indicates crankshaft rotation angle. Indicates the fuel ratio in the premixed combustion stage. This indicates the cumulative combustion mass percentage during the premixed combustion stage. This indicates the parameters for complete combustion during the premixed combustion stage. Indicates the combustion initiation phase of the premixed combustion stage. Indicates the duration of combustion in the premixed combustion stage. The Wiebe shape factor represents the premixed combustion stage. Indicates the fuel proportion during the diffusion combustion stage. This indicates the percentage of cumulative combustion mass during the diffusion combustion phase. Indicates the parameters for complete combustion during the diffusion combustion stage. Indicates the combustion initiation phase of the diffusion combustion stage. Indicates the duration of combustion during the diffusion combustion stage. The Wiebe shape factor representing the diffusion combustion stage. Indicates the fuel ratio in the afterburning stage. This indicates the percentage of total mass burned during the afterburning phase. Indicates the parameters for complete combustion in the afterburning stage. Indicates the combustion initiation phase of the afterburning stage. Indicates the duration of combustion in the afterburning stage. The Wiebe shape factor represents the afterburning stage;

[0021] The formulas for calculating in-cylinder pressure and temperature in the combustion model are as follows:

[0022] First, the energy conservation equation:

[0023] ;

[0024] In the above formula, Indicates the mass of the working fluid in the cylinder. This represents the specific internal energy of the working fluid. This indicates the intake air mass flow rate. Indicates the specific enthalpy of the intake air. Indicates exhaust mass flow rate, The specific enthalpy of the exhaust gas. Indicates the rate of heat release during combustion. Indicates the wall heat transfer loss rate. This represents the work done on the piston;

[0025] Then, the mass conservation equation:

[0026] ;

[0027] In the above formula, Indicates the rate of change of mass inside the cylinder. This represents the sum of the mass flow rates of all gases entering the cylinder. This represents the sum of all mass flow rates leaving the cylinder;

[0028] Finally, the gas law is obtained as follows:

[0029] ;

[0030] In the above formula, Indicates the instantaneous pressure inside the cylinder. Indicates the instantaneous volume inside the cylinder. The gas constant representing the working fluid. Indicates the cylinder temperature;

[0031] The formulas for calculating the indicated work, torque, and power of an engine in a combustion model are as follows:

[0032] First, calculate the indicated work using the indicator diagram. : ;

[0033] Calculate the indicated power again : ;

[0034] Finally, the indicated torque is obtained. : ;

[0035] In the above formula, Indicates engine speed. Indicates the number of engine cylinders. This indicates the stroke coefficient (2 for a four-stroke engine).

[0036] Furthermore, the specific calculation formula for the heat transfer model is as follows:

[0037] ;

[0038] In the above formula, Indicates the instantaneous convective heat transfer coefficient. Indicates the cylinder diameter. Indicates the instantaneous pressure inside the cylinder. Indicates the temperature of the gas inside the cylinder. This indicates the local average gas velocity within the cylinder. , This represents the empirical constant for gas velocity. Indicates the average piston speed. Indicates the displacement of a single cylinder. Indicates the reference state temperature. Indicates the reference state pressure. Indicates the reference state volume. This indicates the instantaneous pressure under engine reversing conditions.

[0039] Furthermore, the injector delivery rate in the fuel injection model The specific calculation formula is as follows:

[0040]

[0041] In the above formula, Indicates volumetric efficiency. This represents the reference density used to calculate volumetric efficiency. Indicates engine speed. Indicates engine displacement. Indicates the engine's air-fuel ratio. Indicates the number of cylinders. Indicates the duration of the jetting.

[0042] Furthermore, the time required for the diesel engine to reach 95% of the set target speed during the process from starting is defined as the starting time. ;

[0043] The environmental parameters, structural parameters, and control parameters of the starting device include the battery open-circuit voltage, starter motor efficiency, starter motor maximum rated power, clutch friction coefficient, start-up oil supply time, and oil-air ratio.

[0044] Analyze the impact of the above parameters on the start-up time. The specific process of the impact is as follows:

[0045] Step 1: Standardize the data to eliminate the influence of units on the results and ensure the fairness of the analysis results, that is:

[0046] ;

[0047] In the above formula, Indicates the sample number. Indicates the parameter number. Indicates the number of samples. This represents the standardized data. Indicates the first The parameter of the first Each sample value Indicates the first The mean of each parameter, Indicates the first The standard deviation of each parameter;

[0048] Step 2: Calculate the Pearson correlation coefficient of the standardized data to assess the linear sensitivity of the parameter, i.e.:

[0049] ;

[0050] In the above formula, Indicates the sample number. Indicates the parameter number. Indicates the number of samples. Indicates the first The Pearson correlation coefficient of each parameter, Indicates the first The parameter of the first A standardized sample value, Indicates the output of the first A standardized sample value, Indicates the first The sample mean of each parameter, This represents the output sample mean;

[0051] Step 3: Calculate the Spearman rank correlation coefficient of the standardized data to assess the sensitivity of the parameters to monotonic relationships, i.e.:

[0052] ;

[0053] In the above formula, Indicates the sample number. Indicates the number of samples. This represents the difference in the ranks of two variables. This represents the Spearman rank correlation coefficient; Step 4: Analyze the joint effect of all input parameters on the output through multiple linear regression, and extract the standardized regression coefficients as sensitivity indicators, i.e.:

[0054] ;

[0055] In the above formula, Indicates the parameter number. Indicates the number of parameters. This represents the standardized output prediction value. Indicates the first A standardized input parameter, Represents the standardized regression coefficients. express and The simple correlation coefficient, express standard deviation express standard deviation express The coefficient of determination of the independent variables in the multivariate analysis;

[0056] Step 5: Calculate the partial correlation coefficient between the standardized data from Step 1 and the output variable. While controlling for the influence of all other parameters, evaluate the pure correlation between this parameter and the output, i.e.:

[0057] ;

[0058] In the above formula, Indicates the set of control variables In the case of variables and The partial correlation coefficient, express and The simple correlation coefficient, express and The correlation coefficient, express and The correlation coefficient;

[0059] Step 6: Combine the results of the four different sensitivity analysis methods into a comprehensive index. This multi-method fusion improves the robustness and reliability of the sensitivity assessment.

[0060] ;

[0061] In the above formula, Indicates the sequence number of the sensitivity analysis method. Indicates the first The overall sensitivity score of each parameter Indicates the first The parameter in the first... Sensitivity scores under this method.

[0062] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0063] (1) This invention significantly reduces R&D costs and time by replacing physical prototype testing with virtual simulation. Sensitivity analysis can identify key parameters affecting start-up time, providing targeted guidance for design improvements.

[0064] (2) By establishing a virtual simulation model, the present invention can accurately reproduce the starting process of a diesel engine on a computer, thereby replacing most of the expensive and time-consuming physical prototypes in the early stage of research and development, and saving the cost of prototype manufacturing and test bench construction.

[0065] (3) The present invention can systematically perform sensitivity analysis. By purposefully changing a series of input parameters and observing their quantitative impact on the key objective of start-up time, it can accurately identify bottleneck factors and eliminate design redundancy. Attached Figure Description

[0066] Figure 1 This is a flowchart of the overall simulation analysis process of the present invention;

[0067] Figure 2 This is a schematic diagram of the overall structure of the one-dimensional simulation model of diesel engine starting in this invention;

[0068] Figure 3 This is a curve showing the change of starter motor torque over time in a specific example as illustrated in the embodiment.

[0069] Figure 4 This is a curve showing the change of engine speed over time in a specific calculation example as illustrated in the embodiment.

[0070] Figure 5These are the sensitivity scores for the first four parameters of the example;

[0071] Figure 6 This is a schematic diagram showing the ranking of the comprehensive scores of parameter sensitivity in the implementation examples. Detailed Implementation

[0072] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention is not limited to the embodiments described.

[0073] like Figure 1 As shown, the simulation analysis method for simulating the diesel engine starting process of the present invention first obtains the operating environment conditions, structural parameters, and control parameters of the power plant diesel engine, and constructs a one-dimensional starting model of the diesel engine based on the obtained parameters; then, the one-dimensional starting model of the diesel engine is used to perform one-dimensional simulation calculations on the starting transient process of the diesel engine, and the influence of different parameters on the starting time of the diesel engine is calculated and simulated; finally, the sensitivity analysis of the simulation results (each parameter) is performed using the comprehensive Pearson correlation coefficient, Spearman rank correlation coefficient, standardized regression coefficient, and partial correlation coefficient.

[0074] In the one-dimensional simulation calculation of the diesel engine's starting transient process, an electric motor is used for reverse dragging until the diesel engine can autonomously inject fuel and reach the target speed. The one-dimensional starting model of the diesel engine includes the following sub-models:

[0075] Sub-model 1, Combustion Model: The combustion model is used to represent the relationship between the combustion heat release rate and the crankshaft angle, calculate the in-cylinder pressure and temperature, and then obtain the engine's indicated work, torque and power.

[0076] Sub-model 2, heat transfer model, is used to predict the heat transfer rate and heat loss between various components of the diesel engine and the working fluid flowing through it; the heat transfer model includes the heat transfer coefficient calculation formula and the local average gas velocity model used to describe the motion state of the working fluid in the cylinder.

[0077] Sub-model 3, fuel injection model. The fuel injection model refers to the fuel injection module with air-fuel ratio pulse, which is used to convert the control parameters of the fuel injection system into quantitative information of the in-cylinder mixture, in order to prepare for the combustion calculation of the mixture.

[0078] Sub-model 4, Intake and Exhaust System: This model simulates the flow of gas in the pipeline, including the air filter, compressor, intercooler, intake manifold, throttle valve, exhaust manifold, turbine, and three-way catalytic converter (the positional and connection relationships of these components follow existing technological principles). It solves for the propagation and changes of pressure, temperature, flow rate, and components in the pipeline.

[0079] Sub-model 5, cylinder assembly, simulates the operation of the cylinder, including the combustion model and heat transfer model mentioned above, as well as the valve timing model and in-cylinder gas properties;

[0080] Sub-model 6, Mechanical System: The mechanical system converts the thermodynamic work generated by the gas pressure in the cylinder into usable shaft work and simulates the rotational dynamics of the crankshaft system.

[0081] like Figure 2 As shown, the diesel engine starting device in the one-dimensional starting model of a diesel engine includes an engine system, a starter motor, a battery pack, and a meshing mechanism. The meshing mechanism is installed between the starter motor and the diesel engine flywheel of the whole machine, and is used to transmit the torque generated by the starter motor to the diesel engine flywheel. The starter motor is installed between the battery pack and the meshing mechanism, and is used to obtain electrical energy from the battery to generate rotational torque to drive the engine flywheel to rotate.

[0082] The engine system includes engine block components, crankshaft and connecting rod mechanism, valve train, fuel system, and turbocharger.

[0083] In the one-dimensional simulation calculation process, firstly, the controller (such as...) Figure 2 As shown, the starter motor (connected to the motor) sends a start command, engages the clutch (installed at the end of the motor output shaft), and causes the battery pack to drive the starter motor to rotate, thereby dragging the engine. When the engine speed reaches the preset autonomous operation threshold, the controller immediately sends a command to disengage the clutch to cut off power transmission and prevent the engine from dragging the starter motor. Then, air enters through the intake inlet, is filtered by the air filter, and is pressurized by the compressor. The pressurized high-pressure air is distributed through the intake manifold and enters each cylinder through the intake valve. The exhaust gas generated by combustion is discharged from the exhaust valve, collected in the exhaust duct, and drives the turbine. The rotation of the turbine drives the coaxial compressor to work, and finally the exhaust gas is treated by the catalytic converter and discharged into the atmosphere.

[0084] The formula describing the change of combustion heat release rate with crankshaft angle in the combustion model is as follows;

[0085] ;

[0086] In the above formula, Indicates the cumulative mass percentage burned. Indicates crankshaft rotation angle. Indicates the fuel ratio in the premixed combustion stage. This indicates the cumulative combustion mass percentage during the premixed combustion stage. This indicates the parameters for complete combustion during the premixed combustion stage. Indicates the combustion initiation phase of the premixed combustion stage. Indicates the duration of combustion in the premixed combustion stage. The Wiebe shape factor represents the premixed combustion stage. Indicates the fuel proportion during the diffusion combustion stage. This indicates the percentage of cumulative combustion mass during the diffusion combustion phase. Indicates the parameters for complete combustion during the diffusion combustion stage. Indicates the combustion initiation phase of the diffusion combustion stage. Indicates the duration of combustion during the diffusion combustion stage. The Wiebe shape factor representing the diffusion combustion stage. Indicates the fuel ratio in the afterburning stage. This indicates the percentage of total mass burned during the afterburning phase. Indicates the parameters for complete combustion in the afterburning stage. Indicates the combustion initiation phase of the afterburning stage. Indicates the duration of combustion in the afterburning stage. This represents the Wiebe shape factor during the afterburning stage.

[0087] The formulas for calculating in-cylinder pressure and temperature in the combustion model are as follows:

[0088] First, the energy conservation equation:

[0089] ;

[0090] In the above formula, Indicates the mass of the working fluid in the cylinder. This represents the specific internal energy of the working fluid. This indicates the intake air mass flow rate. Indicates the specific enthalpy of the intake air. Indicates exhaust mass flow rate, The specific enthalpy of the exhaust gas. Indicates the rate of heat release during combustion. Indicates the wall heat transfer loss rate. This represents the work done on the piston;

[0091] Then, the mass conservation equation:

[0092] ;

[0093] In the above formula, Indicates the rate of change of mass inside the cylinder. This represents the sum of the mass flow rates of all gases entering the cylinder. This represents the sum of all mass flow rates leaving the cylinder;

[0094] Finally, the gas law is obtained as follows:

[0095] ;

[0096] In the above formula, Indicates the instantaneous pressure inside the cylinder. Indicates the instantaneous volume inside the cylinder. The gas constant representing the working fluid. This indicates the temperature inside the cylinder.

[0097] The formulas for calculating the indicated work, torque, and power of an engine in a combustion model are as follows:

[0098] First, calculate the indicated work using the indicator diagram. : ;

[0099] Calculate the indicated power again : ;

[0100] Finally, the indicated torque is obtained. : ;

[0101] In the above formula, Indicates engine speed. Indicates the number of engine cylinders. This represents the stroke coefficient.

[0102] The specific calculation formula for the heat transfer model in this embodiment is as follows:

[0103] ;

[0104] In the above formula, Indicates the instantaneous convective heat transfer coefficient. Indicates the cylinder diameter. Indicates the instantaneous pressure inside the cylinder. Indicates the temperature of the gas inside the cylinder. This indicates the local average gas velocity within the cylinder. , This represents the empirical constant for gas velocity. Indicates the average piston speed. Indicates the displacement of a single cylinder. Indicates the reference state temperature. Indicates the reference state pressure. Indicates the reference state volume. This indicates the instantaneous pressure under engine reversing conditions.

[0105] Injector delivery rate in fuel injection model The specific calculation formula is as follows:

[0106]

[0107] In the above formula, Indicates volumetric efficiency. This represents the reference density used to calculate volumetric efficiency. Indicates engine speed. Indicates engine displacement. Indicates the engine's air-fuel ratio. Indicates the number of cylinders. Indicates the duration of the jetting.

[0108] The starting time is defined as the time required for the diesel engine to reach 95% of the set target speed from start-up. ;

[0109] The environmental parameters, structural parameters, and control parameters of the starting device include the battery open-circuit voltage, starter motor efficiency, starter motor maximum rated power, clutch friction coefficient, start-up oil supply time, and oil-air ratio.

[0110] Analyze the impact of the above parameters on the start-up time. The specific process of the impact is as follows:

[0111] Step 1: Standardize the data to eliminate the influence of units on the results and ensure the fairness of the analysis results, that is:

[0112] ;

[0113] In the above formula, Indicates the sample number. Indicates the parameter number. Indicates the number of samples. This represents the standardized data. Indicates the first The parameter of the first Each sample value Indicates the first The mean of each parameter, Indicates the first The standard deviation of each parameter;

[0114] Step 2: Calculate the Pearson correlation coefficient of the standardized data from Step 1 to assess the linear sensitivity of the parameter, i.e.:

[0115] ;

[0116] In the above formula, Indicates the first The Pearson correlation coefficient of each parameter, Indicates the first The parameter of the first A standardized sample value, Indicates the output of the first A standardized sample value, Indicates the first The sample mean of each parameter, This represents the output sample mean;

[0117] Step 3: Calculate the Spearman rank correlation coefficient of the standardized data from Step 1 to assess the sensitivity of the parameters to monotonic relationships, i.e.:

[0118] ;

[0119] In the above formula, This represents the difference in the ranks of two variables. Represents the Spearman rank correlation coefficient;

[0120] Step 4: Analyze the joint impact of all input parameters on the output using multiple linear regression, and extract the standardized regression coefficients as sensitivity indicators, i.e.:

[0121] ;

[0122] In the above formula, Indicates the number of parameters. This represents the standardized output prediction value. Indicates the first A standardized input parameter, Represents the standardized regression coefficients. express and The simple correlation coefficient, express standard deviation express standard deviation express The coefficient of determination of the independent variables in the multivariate analysis;

[0123] Step 5: Calculate the partial correlation coefficient between the standardized data from Step 1 and the output variable. While controlling for the influence of all other parameters, evaluate the pure correlation between this parameter and the output, i.e.:

[0124] ;

[0125] In the above formula, Indicates the set of control variables In the case of variables and The partial correlation coefficient, express and The simple correlation coefficient, express and The correlation coefficient, express and The correlation coefficient;

[0126] Step 6: Combine the results of the four different sensitivity analysis methods from Steps 2 to 5 into a comprehensive index. This multi-method fusion improves the robustness and reliability of the sensitivity assessment.

[0127] ;

[0128] In the above formula, Indicates the sequence number of the sensitivity analysis method. Indicates the first The overall sensitivity score of each parameter Indicates the first The parameter in the first... Sensitivity scores under this method.

[0129] based on Figure 2 The simulation device for the one-dimensional starting model of the diesel engine selects the battery open-circuit voltage, starter motor efficiency, starter motor maximum rated power, clutch friction coefficient, start fuel supply time and fuel-air ratio as input parameters, and the start time as output parameter to perform simulation calculations of the diesel engine starting process. The simulation calculation data is shown in Table 1.

[0130] Table 1

[0131] Battery open-circuit voltage (V) Starter motor efficiency Maximum rated power of starter motor (kW) clutch friction coefficient Start of fuel supply time (s) Oil-to-gas ratio Startup time (s) 22 0.8 130 0.3 0.5 0.06 10.84 24 0.8 130 0.3 0.5 0.06 10.84 26 0.8 130 0.3 0.5 0.06 10.84 24 0.7 130 0.3 0.5 0.06 11.41 24 0.9 130 0.3 0.5 0.06 11.37 24 0.8 160 0.3 0.5 0.06 11.32 24 0.8 190 0.3 0.5 0.06 11.28 24 0.8 130 0.35 0.5 0.06 11.36 24 0.8 130 0.4 0.5 0.06 11.41 24 0.8 130 0.3 1 0.06 11.41 24 0.8 130 0.3 1.5 0.06 11.41 24 0.8 130 0.3 0.5 0.064 10.44 24 0.8 130 0.3 0.5 0.068 10.12

[0132] Figure 3 , Figure 4 The figures show the curves of the starter motor torque and engine speed changing over time for a specific calculation example.

[0133] Then, based on the above simulation results, sensitivity analysis was conducted on each parameter, calculating the Pearson correlation coefficient, Spearman rank correlation coefficient, standardized regression coefficient, and partial correlation coefficient to obtain the comprehensive sensitivity index. The sensitivity results for the top four parameters in the comprehensive sensitivity index are shown below. Figure 5 As shown, Figure 6 Rank all parameters by their overall sensitivity index.

[0134] Based on the sensitivity analysis results above, the parameters that affect the starting time from highest to lowest are: air-fuel ratio, fuel injection start time, clutch friction coefficient, starter motor maximum rated power, starter motor efficiency, and battery open-circuit voltage. Among these, the air-fuel ratio has the highest impact on the starting time, while the impact of the battery open-circuit voltage is negligible.

[0135] In summary, this invention can identify the main influencing factors of the performance of power plant diesel engine starting process, save the cost of conducting starting tests, and provide targeted guidance for design improvement.

Claims

1. A simulation analysis method for simulating the starting process of a diesel engine, characterized in that, First, the operating environment conditions, structural parameters, and control parameters of the power plant diesel engine are obtained, and a one-dimensional starting model of the diesel engine is constructed based on the obtained parameters. Then, the one-dimensional starting model of the diesel engine is used to perform one-dimensional simulation calculations on the starting transient process of the diesel engine, and the influence of different parameters on the starting time of the diesel engine is calculated and simulated. Finally, the sensitivity analysis of the simulation results (each parameter) is performed using the comprehensive Pearson correlation coefficient, Spearman rank correlation coefficient, standardized regression coefficient, and partial correlation coefficient. In the one-dimensional simulation calculation of the diesel engine's starting transient process, an electric motor is used for reverse dragging until the diesel engine can autonomously inject fuel and reach the target speed. The one-dimensional starting model of the diesel engine includes the following sub-models: Sub-model 1, Combustion Model: The combustion model is used to represent the relationship between the combustion heat release rate and the crankshaft angle, calculate the in-cylinder pressure and temperature, and then obtain the engine's indicated work, torque and power. Sub-model 2, heat transfer model, is used to predict the heat transfer rate and heat loss between various components of the diesel engine and the working fluid flowing through it; the heat transfer model includes the heat transfer coefficient calculation formula and the local average gas velocity model used to describe the motion state of the working fluid in the cylinder. Sub-model 3, fuel injection model. The fuel injection model refers to the fuel injection module with air-fuel ratio pulse, which is used to convert the control parameters of the fuel injection system into quantitative information of the in-cylinder mixture, in order to prepare for the combustion calculation of the mixture. Sub-model 4, intake and exhaust system, simulates the flow of gas in the pipeline and solves for the propagation and changes of pressure, temperature, flow rate and components in the pipeline; Sub-model 5, cylinder assembly, which simulates the operation of a cylinder; Sub-model 6, Mechanical System: The mechanical system converts the thermodynamic work generated by the gas pressure in the cylinder into usable shaft work and simulates the rotational dynamics of the crankshaft system.

2. The simulation analysis method for simulating the starting process of a diesel engine according to claim 1, characterized in that, The diesel engine starting device in the one-dimensional diesel engine starting model includes an engine system, a starter motor, a battery pack, and a meshing mechanism. The meshing mechanism is installed between the starter motor and the diesel engine flywheel of the whole machine, and is used to transmit the torque generated by the starter motor to the diesel engine flywheel. The starter motor is installed between the battery pack and the meshing mechanism, and is used to obtain electrical energy from the battery to generate rotational torque to drive the engine flywheel to rotate. The engine system includes engine block components, crankshaft and connecting rod mechanism, valve train, fuel system and turbocharger; In the one-dimensional simulation calculation, firstly, the controller issues a start command, engages the clutch, and causes the battery pack to drive the starter motor to rotate, thereby dragging the engine. When the engine speed reaches the preset autonomous operation threshold, the controller immediately issues a command to disengage the clutch to cut off power transmission and prevent the engine from dragging the starter motor. Then, air enters through the intake inlet, is filtered by the air filter, and is pressurized by the compressor. The pressurized high-pressure air is distributed through the intake manifold and enters each cylinder through the intake valve. The exhaust gas generated by combustion is discharged from the exhaust valve, collected in the exhaust duct, and drives the turbine. The rotation of the turbine drives the coaxial compressor to work, and finally the exhaust gas is treated by the catalytic converter and discharged into the atmosphere.

3. The simulation analysis method for simulating the starting process of a diesel engine according to claim 1, characterized in that, The formula describing the change of combustion heat release rate with crankshaft angle in the combustion model is as follows; ； In the above formula, Indicates the cumulative mass percentage burned. Indicates crankshaft rotation angle. Indicates the fuel ratio in the premixed combustion stage. This indicates the cumulative combustion mass percentage during the premixed combustion stage. This indicates the parameters for complete combustion during the premixed combustion stage. Indicates the combustion initiation phase of the premixed combustion stage. Indicates the duration of combustion during the premixed combustion stage. The Wiebe shape factor represents the premixed combustion stage. Indicates the fuel proportion during the diffusion combustion stage. This indicates the percentage of cumulative combustion mass during the diffusion combustion phase. Indicates the parameters for complete combustion during the diffusion combustion stage. Indicates the combustion initiation phase of the diffusion combustion stage. Indicates the duration of combustion during the diffusion combustion stage. The Wiebe shape factor representing the diffusion combustion stage. Indicates the fuel ratio in the afterburning stage. This indicates the percentage of total mass burned during the afterburning phase. Indicates the parameters for complete combustion in the afterburning stage. Indicates the combustion initiation phase of the afterburning stage. Indicates the duration of combustion in the afterburning stage. The Wiebe shape factor represents the afterburning stage; The formulas for calculating in-cylinder pressure and temperature in the combustion model are as follows: First, the energy conservation equation: ； In the above formula, Indicates the mass of the working fluid in the cylinder. This represents the specific internal energy of the working fluid. This indicates the intake air mass flow rate. Indicates the specific enthalpy of the intake air. Indicates exhaust mass flow rate, The specific enthalpy of the exhaust gas. Indicates the rate of heat release during combustion. Indicates the wall heat transfer loss rate. This represents the work done on the piston; Then, the mass conservation equation is used to describe Indicates the rate of change of mass inside the cylinder: ； In the above formula, Indicates the rate of change of mass inside the cylinder. This represents the sum of the mass flow rates of all gases entering the cylinder. This represents the sum of all mass flow rates leaving the cylinder; Finally, the gas law is obtained as follows: ； In the above formula, Indicates the instantaneous pressure inside the cylinder. Indicates the instantaneous volume inside the cylinder. The gas constant representing the working fluid. Indicates the cylinder temperature; The formulas for calculating the indicated work, torque, and power of an engine in a combustion model are as follows: First, calculate the indicated work using the indicator diagram. : ; Recalculate the indicated power : ; Finally, the indicated torque is obtained. : ; In the above formula, Indicates engine speed. Indicates the number of engine cylinders. This represents the stroke coefficient.

4. The simulation analysis method for simulating the starting process of a diesel engine according to claim 1, characterized in that, The specific calculation formula for the heat transfer model is as follows: ； In the above formula, Indicates the instantaneous convective heat transfer coefficient. Indicates the cylinder diameter. Indicates the instantaneous pressure inside the cylinder. Indicates the temperature of the gas inside the cylinder. This indicates the local average gas velocity within the cylinder. , This represents the empirical constant for gas velocity. Indicates the average piston speed. Indicates the displacement of a single cylinder. Indicates the reference state temperature. Indicates the reference state pressure. Indicates the reference state volume. This indicates the instantaneous pressure under engine reversing conditions.

5. The simulation analysis method for simulating the starting process of a diesel engine according to claim 1, characterized in that, Injector delivery rate in fuel injection model The specific calculation formula is as follows: ； In the above formula, Indicates volumetric efficiency. This represents the reference density used to calculate volumetric efficiency. Indicates engine speed. Indicates engine displacement. Indicates the engine's air-fuel ratio. Indicates the number of cylinders. Indicates the duration of the jetting.

6. The simulation analysis method for simulating the starting process of a diesel engine according to claim 1, characterized in that, The starting time is defined as the time required for the diesel engine to reach 95% of the set target speed from start-up. ; The environmental parameters, structural parameters, and control parameters of the starting device include the battery open-circuit voltage, starter motor efficiency, starter motor maximum rated power, clutch friction coefficient, start-up oil supply time, and oil-air ratio. Analyze the impact of the above parameters on the start-up time. The specific process of the impact is as follows: Step 1: Standardize the data to eliminate the influence of units on the results and ensure the fairness of the analysis results, that is: ； In the above formula, Indicates the sample number. Indicates the parameter number. Indicates the number of samples. This represents the standardized data. Indicates the first The parameter of the first Each sample value Indicates the first The mean of each parameter, Indicates the first The standard deviation of each parameter; Step 2: Calculate the Pearson correlation coefficient of the standardized data from Step 1 to assess the linear sensitivity of the parameter, i.e.: ； In the above formula, Indicates the first The Pearson correlation coefficient of each parameter, Indicates the first The parameter of the first A standardized sample value, Indicates the output of the first A standardized sample value, Indicates the first The sample mean of each parameter, This represents the output sample mean; Step 3: Calculate the Spearman rank correlation coefficient of the standardized data from Step 1. This coefficient is used to assess the sensitivity of the parameters to monotonic relationships. ； In the above formula, This represents the difference in the ranks of two variables. Represents the Spearman rank correlation coefficient; Step 4: Analyze the joint impact of all input parameters on the output using multiple linear regression, and extract the standardized regression coefficients as sensitivity indicators, i.e.: ； In the above formula, Indicates the number of parameters. This represents the standardized output prediction value. Indicates the first A standardized input parameter, Represents the standardized regression coefficients. express and The simple correlation coefficient, express standard deviation express standard deviation express The coefficient of determination of the independent variables in the multivariate analysis; Step 5: Calculate the partial correlation coefficient between the standardized data from Step 1 and the output variable. While controlling for the influence of all other parameters, evaluate the pure correlation between this parameter and the output, i.e.: ； In the above formula, Indicates the set of control variables In the case of variables and The partial correlation coefficient, express and The simple correlation coefficient, express and The correlation coefficient, express and The correlation coefficient; Step 6: Combine the results of the four different sensitivity analysis methods from Steps 2 to 5 into a comprehensive index. This multi-method fusion improves the robustness and reliability of the sensitivity assessment. ； In the above formula, Indicates the sequence number of the sensitivity analysis method. Indicates the first The overall sensitivity score of each parameter Indicates the first The parameter in the first... Sensitivity scores under this method.

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