Exhaust gas and fresh air mixing uniformity transient simulation method based on intake manifold

Abstract

The invention provides an exhaust gas and fresh air mixing uniformity transient simulation method and system based on an intake manifold, and the method comprises the steps: firstly constructing an intake manifold three-dimensional model, then introducing the intake manifold three-dimensional model into a CFD solver for simulation, and further calculating a simulation result to obtain an EGR rate and an EGR rate deviation; whether the EGR rate and the EGR rate deviation meet threshold values or not is judged so as to judge whether the mixing uniformity reaches the standard or not, when the EGR rate and the EGR rate deviation reach the standard, the mixing uniformity of the waste gas and the fresh air reaches the standard, and the current intake manifold three-dimensional model is output to serve as a target intake manifold three-dimensional model to be manufactured. According to the scheme, the performance of the intake manifold can be evaluated in the forward design stage to obtain the target intake manifold three-dimensional model meeting the requirements, no test is needed, and the design period and cost are greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle simulation, and particularly relates to a transient simulation method for the mixing uniformity of exhaust gas and fresh air based on an intake manifold. Background Art

[0002] The function of an Exhaust Gas Recirculation (EGR) system is to introduce a certain amount of engine combustion exhaust gas into the intake manifold to mix with fresh air, and then introduce it into the combustion chamber for combustion, so as to reduce the oxygen concentration in the cylinder, slow down the combustion speed, and lower the maximum combustion temperature, thereby reducing the formation of harmful pollutant NO X For a multi-cylinder engine, the structure of the intake system will affect the flow field distribution in the cylinder and the intake non-uniformity. The intake non-uniformity of each cylinder will directly affect the mixing degree of air and fuel in each cylinder, thus affecting the organization of the combustion process and ultimately resulting in differences in the combustion processes of each cylinder. Therefore, the structure and layout of the intake pipe and EGR pipe directly affect the combustion quality of each cylinder and the performance of the engine. The EGR rate of each cylinder on a multi-cylinder engine is non-uniform, resulting in a low oxygen concentration and high emission smoke density in the cylinder with a high EGR rate, and the cylinder with a low EGR rate cannot effectively reduce the maximum temperature, and the formation of NOX cannot be effectively controlled, directly affecting the engine operating condition stability, fuel consumption, and emissions. Improving the EGR distribution uniformity of each cylinder of the engine is of great significance for meeting more stringent emission regulations and obtaining the best fuel economy.

[0003] In the prior art, traditional evaluation methods all obtain results through bench tests. It is necessary to wait until the detailed design is completed, purchase sample parts, build a bench for multiple rounds of tests to evaluate, which is time-consuming and laborious. Once it is found that the mixing uniformity does not meet the standard, the intake manifold needs to be optimized again, resulting in a too long design cycle and high cost. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a transient simulation method for the mixing uniformity of exhaust gas and fresh air based on an intake manifold, which is used to solve the technical problems of long design cycle and high cost of the intake manifold in the prior art.

[0005] The present invention provides a transient simulation method for the mixing uniformity of exhaust gas and fresh air based on an intake manifold, including:

[0006] Obtain the three-dimensional model of the intake manifold of the engine and the performance parameters of the CFD solver adapted to the intake manifold; the intake manifold includes an intake pipe, a plurality of branch pipes, and an EGR pipe, obtain the periodic boundary conditions of the intake pipe inlet, the branch pipe outlet, and the EGR pipe inlet, and obtain the intake manifold assembly grid model according to the three-dimensional model of the intake manifold;

[0007] Set the CFD solver according to the intake manifold assembly grid model and the CFD solver performance parameters to define the solution objectives and select the solution equations. Analyze and calculate the EGR uniformity of the intake manifold using the set CFD solver to obtain the analysis results. The analysis results include the convergence index and the CFD solver output results. The CFD solver output results include the mass flow rate at the branch outlet and the EGR mass fraction. Calculate the EGR rate and the EGR rate deviation at the outlet of each branch of each cylinder according to the mass flow rate at the branch outlet and the EGR mass fraction.

[0008] Judge whether the EGR rate and the EGR rate deviation meet the thresholds respectively.

[0009] If so, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and output the current three-dimensional model of the intake manifold.

[0010] The above transient simulation method for the mixing uniformity of exhaust gas and fresh air based on the intake manifold first constructs a three-dimensional model of the intake manifold, then imports the three-dimensional model of the intake manifold into the CFD solver for simulation to further calculate the EGR rate and the EGR rate deviation from the simulation results, and judges whether the EGR rate and the EGR rate deviation meet the thresholds respectively to determine whether the mixing uniformity meets the standard. When the EGR rate and the EGR rate deviation meet the standards respectively, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and output the current three-dimensional model of the intake manifold as the target three-dimensional model of the intake manifold for manufacturing, so that this solution can evaluate the performance of the intake manifold in the forward design stage to obtain a target three-dimensional model of the intake manifold that meets the requirements without conducting tests, greatly reducing the design cycle and cost.

[0011] In addition, according to the above transient simulation method for the mixing uniformity of exhaust gas and fresh air based on the intake manifold of the present invention, the following additional technical features may also be included:

[0012] Furthermore, the analysis results also include the convergence index. Before the step of calculating the EGR rate and the EGR rate deviation at the outlet of each branch of each cylinder according to the mass flow rate at the branch outlet and the EGR mass fraction, the following steps are also included:

[0013] Obtain the convergence index from the analysis results respectively. The convergence index includes the EGR mass flow rate at each branch outlet and the EGR rate of the EGR mass flow rate changing with the crankshaft angle at each branch outlet.

[0014] Judge whether the convergence index converges.

[0015] If the convergence index converges, calculate the EGR rate and the EGR rate deviation at the outlet of each branch of each cylinder according to the CFD solver output results; if there is a non-converging convergence index, reset the solver according to the non-converging index until the convergence index converges.

[0016] Further, the steps of obtaining the intake manifold assembly grid model according to the three-dimensional model of the intake manifold include:

[0017] Obtaining the intake manifold surface grid model according to the three-dimensional model of the intake manifold;

[0018] Importing the intake manifold surface grid model into the CFD solver to generate a closed line grid;

[0019] Obtaining the volume grid model according to the generated closed line grid and the defined parameters that need to be refined.

[0020] Further, the steps of analyzing and calculating the EGR uniformity of the intake manifold according to the set CFD solver to obtain the analysis result include:

[0021] Performing transient CFD calculations according to the three-dimensional model of the engine's intake manifold and the periodic boundary conditions to obtain the EGR mass flow rate passing through the outlets of each branch pipe in the intake manifold within ten working cycles of the engine, the EGR rate of the EGR mass flow rate at the outlet of each branch pipe varying with the crankshaft angle, and the flow conditions in the intake pipe at different crankshaft angles.

[0022] Further, the calculation method of the EGR rate is:

[0023]

[0024] where m i is the mass flow rate at the outlet of the branch pipe of the i-th cylinder; θ is the crankshaft angle; EGR θ is the EGR rate of the EGR mass flow rate at the outlet of the branch pipe of the i-th cylinder varying with the crankshaft angle; EGR i is the EGR rate of the i-th cylinder.

[0025] Further, the calculation formula for the deviation of the EGR rate of each cylinder is:

[0026]

[0027] where △EGR i is the EGR rate deviation of the i-th cylinder; EGR 总 is the total EGR rate.

[0028] Further, in the step of judging whether the EGR rate and the EGR rate deviation respectively meet the thresholds, the evaluation criteria for the EGR rate are: when the difference between the maximum and minimum EGR rates of each cylinder is less than 10% of the average EGR rate, the mixing uniformity of the exhaust gas and fresh air meets the standard;

[0029] The evaluation criteria for the EGR rate deviation are:

[0030] When the EGR rate deviation value of each cylinder is less than 10%, the exhaust gas distribution of each cylinder is uniform.

[0031] Further, after the steps of judging whether the EGR rate and the EGR rate deviation respectively meet the thresholds, the following steps are further included: when the EGR rate and the EGR rate deviation do not meet the thresholds, the three-dimensional model of the intake manifold is optimized until the EGR rate and the EGR rate deviation respectively meet the thresholds.

[0032] On the other hand, the present invention provides a transient simulation system for the mixing uniformity of exhaust gas and fresh air based on an intake manifold, and the system includes:

[0033] An acquisition module, configured to acquire a three-dimensional model of the intake manifold of the engine and performance parameters of a CFD solver adapted to the intake manifold; the intake manifold includes an intake pipe, a plurality of branch pipes and an EGR pipe, and acquire periodic boundary conditions at the inlet of the intake pipe, the outlet of the branch pipe and the inlet of the EGR pipe, and obtain a grid model of the intake manifold assembly according to the three-dimensional model of the intake manifold;

[0034] An analysis module, configured to set a CFD solver according to the grid model of the intake manifold assembly and the performance parameters of the CFD solver to define a solution target and select a solution equation, analyze and calculate the EGR uniformity of the intake manifold according to the set CFD solver to obtain an analysis result, the analysis result includes a convergence index and an output result of the CFD solver, the output result of the CFD solver includes the mass flow rate at the outlet of the branch pipe and the EGR mass fraction, and calculate the EGR rate and the EGR rate deviation at the outlet of each branch pipe of each cylinder according to the mass flow rate at the outlet of the branch pipe and the EGR mass fraction;

[0035] A judgment module, configured to judge whether the EGR rate and the EGR rate deviation respectively meet the thresholds;

[0036] A first execution module, configured to when both the EGR rate and the EGR rate deviation meet the thresholds, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and output the current three-dimensional model of the intake manifold. Description of the Drawings

[0037] Figure 1 It is a flowchart of a transient simulation method for the mixing uniformity of exhaust gas and fresh air based on an intake manifold in an embodiment of the present invention;

[0038] Figure 2 It is a schematic structural diagram of an intake manifold in an embodiment of the present invention.

[0039] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. Specific Embodiments

[0040] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0042] To solve the technical problems of long design cycle and high cost of the intake manifold in the prior art, the present application provides a transient simulation method for the mixing uniformity of exhaust gas and fresh air based on the intake manifold. By first constructing a three-dimensional model of the intake manifold and then importing the three-dimensional model of the intake manifold into a CFD solver for simulation to further calculate the EGR rate and the EGR rate deviation from the simulation results, and determining whether the EGR rate and the EGR rate deviation meet the thresholds respectively to determine whether the mixing uniformity meets the standard. When the EGR rate and the EGR rate deviation meet the standards respectively, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and the current three-dimensional model of the intake manifold is output as the target three-dimensional model of the intake manifold for manufacturing, so that the present solution can evaluate the performance of the intake manifold in the forward design stage to obtain a target three-dimensional model of the intake manifold that meets the requirements without conducting tests, greatly reducing the design cycle and cost.

[0043] Specifically, the main idea of using the CFD (Computational Fluid Dynamics) method to calculate the EGR (Exhaust Gas Recirculation) distribution uniformity of each cylinder of a four-cylinder engine in this solution is as follows: First, perform one-dimensional thermodynamic calculations of the engine to obtain the periodic boundary conditions at the inlet and outlet of the intake manifold and the inlet of the EGR pipe; then perform three-dimensional transient CFD calculations to obtain the EGR mass flow rate at the outlet of each branch pipe in each intake manifold, the EGR rate of the EGR mass flow rate at the outlet of each branch pipe varying with the crankshaft angle, and the flow conditions in the intake pipe at different crankshaft angles; finally, by analyzing the EGR rate and the EGR rate uniformity deviation (hereinafter referred to as: EGR rate deviation) of each cylinder, obtain the EGR uniformity distribution of the intake manifold at different crankshaft angles.

[0044] The flow condition of the recirculated exhaust gas in the intake pipe can be observed through the slices and animations of the simulation results, and the influence of structural factors on the uniformity of the EGR rate distribution in each cylinder can be analyzed, providing a theoretical basis for model optimization.

[0045] To facilitate the understanding of the present invention, several embodiments of the present invention will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0046] Embodiment 1

[0047] Please refer to Figure 1 , which shows a transient simulation method for the mixing uniformity of exhaust gas and fresh air based on an intake manifold in the first embodiment of the present invention. The method includes steps S101 to S105:

[0048] S101. Obtain the three-dimensional model of the engine's intake manifold and the performance parameters of the CFD solver adapted to the intake manifold; obtain the periodic boundary conditions at the intake pipe inlet, the branch pipe outlet, and the EGR pipe inlet, and obtain the intake manifold assembly grid model according to the three-dimensional model of the intake manifold.

[0049] As Figure 2 shown, the intake manifold includes an intake pipe, a plurality of branch pipes, and an EGR pipe. The intake pipe serves as the fresh air inlet, the EGR pipe serves as the exhaust gas inlet, and the branch pipes serve as the outlets of each cylinder. As a specific example, in this embodiment, the intake manifold includes 8 branch pipes, and every 2 branch pipes form a whole, which are respectively used for the outlets of cylinder 1, cylinder 2, cylinder 3, and cylinder 4. Specifically, the required boundary conditions can be obtained from bench tests or calculated by one-dimensional thermodynamic software, including the data of the variation relationship of the mass flow rate and static temperature of the fresh air inlet and the exhaust gas inlet with the crankshaft angle, and the data of the variation relationship of the mass flow rate of each outlet with the crankshaft angle. It should be noted that the variation range of the given data should be greater than the crankshaft angle range required for CFD calculation, and the simulation needs to be carried out for at least ten working cycles.

[0050] In this embodiment, the step of obtaining the intake manifold assembly grid model according to the three-dimensional model of the intake manifold includes: obtaining the intake manifold surface grid model according to the three-dimensional model of the intake manifold; importing the intake manifold surface grid model into the CFD solver to generate a closed line grid; and obtaining the volume grid model according to the generated closed line grid and the defined parameters to be refined.

[0051] Generating a grid means dividing a spatially continuous computational domain into many sub-regions and determining the node coordinates in each region. During the grid generation process, the quality of the generated grid has a decisive impact on the numerical simulation of fluid flow. It not only affects the calculation time and convergence speed but also the calculation accuracy. From the perspective of ensuring calculation accuracy, when modeling, it is generally necessary to ensure as much as possible the consistency between the computational domain and the actual fluid flow domain. The smaller the divided grid, the better the body-fitting property. Additionally, for the regions of concern, in order to obtain the three-dimensional result values of more computational points in these regions, it is also required to divide the computational grid smaller. However, for a certain computational space, the smaller the grid, the more grid cells there are, which will significantly increase the calculation time.

[0052] After generating the volume mesh, perform inlet and outlet stretching on the intake manifold, exhaust gas inlet pipe, and outlet pipe, and combine them into a new volume mesh. The new volume mesh needs to redefine the inlet and outlet boundaries.

[0053] Check the quality of the generated volume mesh. The quality of the mesh has a great impact on whether the calculation can proceed normally, as well as the calculation time and accuracy.

[0054] S102. Set the CFD solver according to the intake manifold combined volume mesh model and the performance parameters of the CFD solver to define the solution objectives and select the solution equations. Analyze and calculate the EGR uniformity of the intake manifold based on the set CFD solver to obtain the analysis results. The analysis results include the convergence index and the output results of the CFD solver. The output results of the CFD solver include the mass flow rate at the branch pipe outlet and the EGR mass fraction. Calculate the EGR rate and EGR rate deviation at the outlet of each cylinder and each branch pipe based on the mass flow rate at the branch pipe outlet and the EGR mass fraction.

[0055] After generating the volume mesh, it is necessary to define the solution objectives and select the corresponding solution equations, that is, the settings of the solver. Specifically as follows:

[0056] 1. Run Mode

[0057] The simulation model is a transient simulation. When performing CFD analysis on the EGR uniformity of the intake manifold, select Crank - Angle for Run Mode, set the change step size to 1 degree, the starting angle to 0, and the termination calculation angle to 10 working cycles, that is, 7200 degrees; the engine speed is the speed under the simulation working conditions, that is, the given parameter. And activate the combustion model.

[0058] 2. Boundary Condition

[0059] The setting of the boundary values directly affects the calculation results. Try to give accurate values that conform to the actual situation as much as possible.

[0060] The mass flow rate and static temperature parameters at the inlet boundary are set to the given operating condition parameters. The air-fuel ratio at the fresh air inlet is 0, and the air-fuel ratio at the EGR inlet is the given value. The inlet turbulent velocity is the given value, and the recommended value of % of mean velocity is 5% - 10%. Only the mass flow rate needs to be given at the outlet boundary.

[0061] The parameters of the wall boundary are given by experiments or one-dimensional calculation results.

[0062] 3.Initial Condition Initialization settings

[0063] Among the initialization parameters, including the parameter definition of the global mixture refinement boundary, only two of the temperature, pressure, and density need to be given, and the others are automatically calculated. The initialization parameters are generally the first step of calculation, and the definition should be reasonable. After setting the global data, set the initialization parameters of the pipeline.

[0064] 4.Solver control Solution control

[0065] Discretization is used to calculate the boundary values and derivatives. For the calculation of boundary values, external difference calculation is selected, and for the calculation of derivatives, the least squares method is selected. The algorithm is Simple, and the settings of other parameters are the same as those of the general solver.

[0066] The turbulence model Turbulence uses the k-z-f or k-e model, the wall treatment for heat transfer selects the Hybrid Wall Treatment, and the heat transfer wall model for the wall selects the Standard WallFunction.

[0067] 5.Output control Output control

[0068] To facilitate viewing the corresponding interface output parameters, first select the calculation for each time step in Write 2D result file, and select the parameters and boundaries to be output.

[0069] For the viewing items of the 2D output results, a formula for pressure and mass flow rate is given for each outlet interface.

[0070] 6.Combustion Combustion model

[0071] The combustion model was activated in the initial run mode. Now, set the interfaces for which the results need to be output in this mode, mainly the EGR mean residual gas mass fraction in the outlet section. The data obtained is used for the final analysis and calculation of EGR uniformity.

[0072] Through the CFD analysis and calculation of the EGR uniformity in the engine intake manifold, the obtained results include the calculation convergence index and the output results set by the solver. Among them, the residual gas EGR mass percentage Comb:ResidualGas Fraction at each airway interface and the mass flow at each outlet Flow:Mass Flow need to be exported for post-processing calculation to compare the EGR rates and EGR rate deviations at each outlet of each cylinder.

[0073] After the simulation software calculation, 2D data results are obtained, and the mass flow and EGR mass fraction at each outlet are exported. The EGR uniformity analysis mainly focuses on parameter information such as the EGR mass fraction and the inlet mass flow at each outlet interface.

[0074] In this embodiment, the steps of analyzing and calculating the EGR uniformity of the intake manifold according to the set CFD solver to obtain the analysis results include: performing transient CFD calculations based on the three-dimensional model of the engine intake manifold and the periodic boundary conditions to obtain the EGR mass flow through the outlets of each branch pipe in the intake manifold of the engine within ten working cycles, the EGR rate of the EGR mass flow at the outlets of each branch pipe varying with the crankshaft angle, and the flow conditions in the intake pipe at different crankshaft angles.

[0075] After the calculation of ten working cycles, the results are already very stable. Take the results of the last working cycle, that is, the results of the last 720° for further formula calculation to obtain the EGR rate and the EGR rate deviation of each cylinder. Specifically as follows:

[0076] The calculation method of the EGR rate is:

[0077]

[0078] In the formula, m i is the mass flow at the outlet of the branch pipe of the i-th cylinder; θ is the crankshaft angle; EGR θ is the EGR rate of the EGR mass flow at the outlet of the branch pipe of the i-th cylinder varying with the crankshaft angle; EGR i is the EGR rate of the i-th cylinder.

[0079] The calculation method formula of the EGR rate deviation of each cylinder is:

[0080]

[0081] In the formula, △EGR i is the EGR rate deviation of the i-th cylinder, i = 1, 2, 3, 4; EGR 总 is the total EGR rate.

[0082] S103. Judge whether the EGR rate and the EGR rate deviation respectively meet the thresholds.

[0083] The EGR rate of each cylinder can be calculated through the EGR rate calculation method and the EGR rate deviation calculation method for each cylinder, and then the average EGR rate of each cylinder can be obtained. Specifically, the evaluation criteria for the EGR rate are as follows: when the difference between the maximum and minimum EGR rates of each cylinder is less than 10% of the average EGR rate, the mixing uniformity of the exhaust gas and fresh air meets the standard. The evaluation criteria for the EGR rate deviation are as follows: when the EGR rate deviation value of each cylinder is less than 10%, the exhaust gas distribution of each cylinder is uniform.

[0084] When the EGR rate and the EGR rate deviation respectively meet the thresholds, step S104 is executed;

[0085] When the EGR rate and the EGR rate deviation do not meet the thresholds, step S105 is executed;

[0086] S104. The mixing uniformity of the exhaust gas and fresh air meets the standard, and the current three-dimensional model of the intake manifold is output.

[0087] S105. Optimize the three-dimensional model of the intake manifold until the EGR rate and the EGR rate deviation respectively meet the thresholds.

[0088] Exhaust gas recirculation (EGR) can effectively reduce NO X emissions. For a multi-cylinder diesel engine adopting the EGR technology, if the exhaust gas distribution of each cylinder is uneven, it will affect its combustion stability and cause the inconsistency of each cylinder's operation. The CFD software is used to perform CFD calculations on the EGR rate uniformity of each cylinder of the intake manifold to evaluate whether the EGR enters each cylinder evenly, and the intake uniformity and EGR rate deviation of each cylinder at different crank angles. In the engine design stage, CFD analysis is carried out on the improvement scheme to obtain the improvement effect, and a further feasible and complete improvement scheme is proposed, which greatly shortens the development cycle and reduces the cost.

[0089] As a specific example, the analysis results also include convergence indicators, and the convergence indicators include the EGR mass flow rate at the outlet of each branch pipe and the EGR rate of the EGR mass flow rate changing with the crank angle at the outlet of each branch pipe. In order to avoid affecting the final design result of the intake manifold due to too divergent calculation results, in this embodiment, before the step of calculating the EGR rate and the EGR rate deviation of each cylinder at the outlet of each branch pipe according to the mass flow rate at the outlet of the branch pipe and the EGR mass fraction, it also includes:

[0090] Obtain the convergence indicators respectively according to the analysis results; judge whether the convergence indicators converge; if the convergence indicators converge, calculate the EGR rate and the EGR rate deviation of each cylinder at the outlet of each branch pipe according to the output result of the CFD solver; if there is a non-convergent convergence indicator, reset the solver according to the non-convergent indicator until the convergence indicators converge.

[0091] In summary, in the above embodiments of the present invention, the transient simulation method for the mixing uniformity of exhaust gas and fresh air based on the intake manifold first constructs a three-dimensional model of the intake manifold, and then imports the three-dimensional model of the intake manifold into a CFD solver for simulation to further calculate the EGR rate and the EGR rate deviation from the simulation results. It is determined whether the EGR rate and the EGR rate deviation meet the thresholds respectively to determine whether the mixing uniformity meets the standard. When the EGR rate and the EGR rate deviation meet the standards respectively, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and the current three-dimensional model of the intake manifold is output as the target three-dimensional model of the intake manifold for manufacturing. This solution can evaluate the performance of the intake manifold in the forward design stage to obtain a target three-dimensional model of the intake manifold that meets the requirements, without the need for experiments, greatly reducing the design cycle and cost.

[0092] Embodiment 2

[0093] The second embodiment of the present invention provides a transient simulation system for the mixing uniformity of exhaust gas and fresh air based on the intake manifold. The system includes:

[0094] An acquisition module for acquiring the three-dimensional model of the intake manifold of the engine and the performance parameters of the CFD solver adapted to the intake manifold; the intake manifold includes an intake pipe, a plurality of branch pipes, and an EGR pipe. The periodic boundary conditions at the inlet of the intake pipe, the outlet of the branch pipe, and the inlet of the EGR pipe are acquired, and an intake manifold assembly grid model is obtained according to the three-dimensional model of the intake manifold;

[0095] An analysis module for setting the CFD solver according to the intake manifold assembly grid model and the performance parameters of the CFD solver to define the solution target and select the solution equation, and analyzing and calculating the EGR uniformity of the intake manifold according to the set CFD solver to obtain an analysis result. The analysis result includes a convergence index and the output result of the CFD solver. The output result of the CFD solver includes the mass flow rate at the outlet of the branch pipe and the EGR mass fraction. The EGR rate and the EGR rate deviation at the outlet of each branch pipe of each cylinder are calculated according to the mass flow rate at the outlet of the branch pipe and the EGR mass fraction;

[0096] A judgment module for judging whether the EGR rate and the EGR rate deviation meet the thresholds respectively;

[0097] A first execution module for when both the EGR rate and the EGR rate deviation meet the thresholds, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and the current three-dimensional model of the intake manifold is output.

[0098] In summary, for the transient simulation system for the mixing uniformity of exhaust gas and fresh air based on the intake manifold in the above embodiments of the present invention, by first constructing a three-dimensional model of the intake manifold and then importing the three-dimensional model of the intake manifold into a CFD solver for simulation to further calculate the EGR rate and the EGR rate deviation from the simulation results, and determining whether the EGR rate and the EGR rate deviation meet the thresholds respectively to determine whether the mixing uniformity meets the standard. When the EGR rate and the EGR rate deviation meet the standards respectively, the mixing uniformity of the exhaust gas and the fresh air meets the standard, and the current three-dimensional model of the intake manifold is output as the target three-dimensional model of the intake manifold for manufacturing. This enables the proposed solution to evaluate the performance of the intake manifold in the forward design stage to obtain a target three-dimensional model of the intake manifold that meets the requirements, without the need for experiments, greatly reducing the design cycle and cost.

[0099] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device. As used in this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0100] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following well-known technologies in the art can be used: discrete logic circuits with logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits with appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0101] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0102] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A transient simulation method for the uniformity of exhaust gas and fresh air mixing based on an intake manifold, characterized in that: include: Acquire a three-dimensional model of an intake manifold of an engine and performance parameters of a CFD solver adapted to the intake manifold; the intake manifold includes an intake pipe, a plurality of branch pipes, and an EGR pipe, obtain periodic boundary conditions of an intake pipe inlet, a branch pipe outlet, and an EGR pipe inlet, and obtain an intake manifold assembly mesh model according to the three-dimensional model of the intake manifold; According to the intake manifold assembly grid model and the CFD solver performance parameters, a CFD solver is set to define a solution target and select a solution equation, and according to the set CFD solver, the intake manifold EGR uniformity is analyzed and calculated to obtain an analysis result, wherein the analysis result includes a convergence index and a CFD solver output result, and the CFD solver output result includes a mass flow rate and an EGR mass fraction at a branch pipe outlet, and the EGR rate and the EGR rate deviation at each branch pipe outlet of each cylinder are calculated according to the mass flow rate and the EGR mass fraction at the branch pipe outlet; Determine whether the EGR rate and the EGR rate deviation meet the thresholds respectively; If so, the mixing uniformity of exhaust gas and fresh air meets the standard, and the current intake manifold three-dimensional model is output.

2. The transient simulation method for exhaust gas and fresh air mixing uniformity based on intake manifold according to claim 1, characterized in that: The analysis result also includes a convergence index. Before the step of calculating the EGR rate and the EGR rate deviation of each branch pipe outlet of each cylinder according to the mass flow rate of the branch pipe outlet and the EGR mass fraction, the step also includes: According to the analysis results, convergence indexes are obtained respectively, and the convergence indexes include the EGR mass flow rate at the outlet of each branch pipe and the EGR rate of the EGR mass flow rate at the outlet of each branch pipe changing with the crankshaft angle; Determine whether the convergence index converges; If the convergence index converges, the EGR rate and EGR rate deviation of each branch pipe outlet of each cylinder are calculated based on the output results of the CFD solver; If there are convergence indicators that do not converge, the solver is reset according to the non-convergent indicators until the convergence indicators converge.

3. The transient simulation method for exhaust gas and fresh air mixing uniformity based on intake manifold according to claim 1, characterized in that: The step of obtaining the intake manifold assembly grid model according to the intake manifold three-dimensional model comprises: Obtaining an intake manifold surface mesh model according to the intake manifold three-dimensional model; Importing the intake manifold surface mesh model into a CFD solver to generate a closed line mesh; The volume mesh model is obtained based on the generated closed line mesh and the parameters that need to be refined.

4. The transient simulation method for exhaust gas and fresh air mixing uniformity based on intake manifold according to claim 1, characterized in that: The steps of analyzing and calculating the intake manifold EGR uniformity according to the set CFD solver to obtain the analysis results include: Transient CFD calculations are performed based on the three-dimensional model of the engine's intake manifold and periodic boundary conditions to obtain the EGR mass flow rate flowing through the outlets of each branch pipe in the intake manifold of the engine in ten working cycles, the EGR rate of the EGR mass flow rate at the outlet of each branch pipe changing with the crankshaft angle, and the flow conditions in the intake pipe at different crankshaft angles.

5. The transient simulation method for exhaust gas and fresh air mixing uniformity based on an intake manifold according to claim 4, characterized in that: The calculation method of EGR rate is: In the formula, m i is the mass flow rate at the outlet of the i-th cylinder branch pipe; θ is the crankshaft angle; EGR θ is the EGR rate of the EGR mass flow at the outlet of the i-th cylinder branch pipe changing with the crankshaft angle; i is the EGR rate of the i-th cylinder.

6. The transient simulation method for exhaust gas and fresh air mixing uniformity based on an intake manifold according to claim 5, characterized in that: The calculation method of EGR rate deviation of each cylinder is: Where, △EGR i is the EGR rate deviation of the i-th cylinder; EGR 总 is the total EGR rate.

7. The transient simulation method for exhaust gas and fresh air mixing uniformity based on an intake manifold according to claim 1, characterized in that: In the step of determining whether the EGR rate and the EGR rate deviation meet the threshold values, the evaluation criteria of the EGR rate are: When the difference between the maximum and minimum EGR rates of each cylinder is less than 10% of the average EGR rate, the mixing uniformity of exhaust gas and fresh air meets the standard; The evaluation criteria for EGR rate deviation are: When the EGR rate deviation of each cylinder is less than 10%, the exhaust gas of each cylinder is evenly distributed.

8. The transient simulation method for exhaust gas and fresh air mixing uniformity based on intake manifold according to claim 1, characterized in that: After the step of determining whether the EGR rate and the EGR rate deviation meet the thresholds respectively, the method further includes: When the EGR rate and the EGR rate deviation do not satisfy the threshold, the intake manifold three-dimensional model is optimized until the EGR rate and the EGR rate deviation satisfy the threshold respectively.

9. A transient simulation system for exhaust gas and fresh air mixing uniformity based on an intake manifold, characterized in that: The system comprises: An acquisition module is used to acquire a three-dimensional model of an intake manifold of an engine and performance parameters of a CFD solver adapted to the intake manifold; the intake manifold includes an intake pipe, a plurality of branch pipes and an EGR pipe, and periodic boundary conditions of an intake pipe inlet, a branch pipe outlet and an EGR pipe inlet are acquired, and a mesh model of an intake manifold assembly is obtained according to the three-dimensional model of the intake manifold; an analysis module, used for setting a CFD solver according to the intake manifold assembly grid model and CFD solver performance parameters to define a solution target and select a solution equation, analyzing and calculating the intake manifold EGR uniformity according to the set CFD solver to obtain an analysis result, wherein the analysis result includes a convergence index and a CFD solver output result, the CFD solver output result includes a mass flow rate and an EGR mass fraction at a branch pipe outlet, and calculating an EGR rate and an EGR rate deviation at each branch pipe outlet of each cylinder according to the mass flow rate and the EGR mass fraction at the branch pipe outlet; A judgment module, used to judge whether the EGR rate and the EGR rate deviation meet the threshold values ​​respectively; The first execution module is used to output the current intake manifold three-dimensional model when the EGR rate and the EGR rate deviation both meet the threshold value and the mixing uniformity of the exhaust gas and the fresh air meets the standard.

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