Modeling method of one-dimensional CFD simulation analysis model of automobile intake and exhaust system

Abstract

The present invention discloses a modeling method of a one-dimensional CFD simulation analysis model of an automobile intake and exhaust system, comprising the following steps: S1, establishing a finite element model of the intake and exhaust system, wherein the finite element model does not include components irrelevant to gas flow; S2, extracting the pipeline closed surface in the finite element model and meshing the pipeline closed surface, extracting the shell closed surface in the finite element model and meshing the shell closed surface, and exporting the pipeline closed surface and the shell closed surface as geometric model files in STL format; S3, importing the geometric model files of the pipeline closed surface and the shell closed surface into GT software, and using the GEM‑3D tool of the GT software to convert the pipeline closed surface and the shell closed surface into pipeline and shell solid models; S4, adding components irrelevant to gas flow to the pipeline and shell solid models, establishing a three-dimensional solid model of the intake and exhaust system, and obtaining a one-dimensional CFD simulation analysis model of the intake and exhaust system through discrete processing. It can ensure modeling accuracy and improve modeling efficiency.

Description

Technical Field

[0001] The invention relates to an automobile intake and exhaust system, and in particular to a modeling method of a one-dimensional CFD simulation analysis model of an automobile intake and exhaust system. Background Art

[0002] GT-SUITE is a multi-physics simulation and analysis software platform developed by Gamma Technologies. As a vehicle and internal combustion engine performance simulation and analysis platform, it has been widely used in the automotive and internal combustion engine industries. Among them, GT-Power, the engine thermodynamic performance simulation and analysis software, is mainly used for the simulation and analysis of internal combustion engine power, economy and intake and exhaust noise.

[0003] In order to accurately simulate the power, economy and intake and exhaust noise of the engine, it is necessary to establish a high-quality one-dimensional engine performance model that retains sufficient intake and exhaust gas path geometric features. GT-SUITE provides the GEM-3D tool, which can easily import and convert certain specific formats of 3D CAD digital models into solid models of the GEM-3D tool, and finally generate and export the one-dimensional CFD simulation analysis model used by the GT-Power module through discrete generation. According to the user manual and case tutorials of the software, a simple gas path model (the basic components of the gas path have no overlap in the flow direction and are only connected in sequence) can easily complete the conversion from three-dimensional to one-dimensional. However, for a more complex system such as an automobile exhaust system including a muffler (the basic components of the gas path overlap in the flow direction, such as the pipes inside the muffler), the case provided by the GT-SUITE software is to establish the corresponding components one by one in GEM-3D according to the geometric parameters of the exhaust system, that is, to use GEM-3D as a CAD tool to establish a three-dimensional solid model of the gas path. There are many parameters to be collected, and because the 3D modeling capabilities provided by GEM-3D are quite basic, it takes engineers 3 to 5 working days to establish a complete intake and exhaust system model according to this method. Obviously, the efficiency is not high, and the three-dimensional CAD digital model that has been completed by the design engineer is not fully utilized. In addition, if the basic component template modeling is used directly in GT-Power without GEM-3D software, a considerable number of geometric features of the intake and exhaust system will inevitably be lost, and a system model with sufficient accuracy cannot be obtained. Therefore, it is urgent to develop a modeling method for a one-dimensional CFD simulation analysis model of an automobile intake and exhaust system that ensures accuracy. Summary of the invention

[0004] The purpose of the present invention is to provide a modeling method for a one-dimensional CFD simulation analysis model of an automobile intake and exhaust system, which can ensure modeling accuracy and improve modeling efficiency.

[0005] The modeling method of the one-dimensional CFD simulation analysis model of the automobile intake and exhaust system of the present invention comprises the following steps:

[0006] S1, establishing a finite element model of an intake and exhaust system, wherein the finite element model does not include components irrelevant to gas flow;

[0007] S2, using finite element software to extract the pipeline closed surface in the finite element model and perform mesh processing on the pipeline closed surface, extract the shell closed surface in the finite element model and perform mesh processing on the shell closed surface, and export the meshed pipeline closed surface and shell closed surface into a geometric model file in STL format;

[0008] S3, importing the geometric model files of the pipeline closed surface and the shell closed surface into the GT software, and using the GEM-3D tool of the GT software to convert the pipeline closed surface and the shell closed surface into pipeline and shell solid models;

[0009] S4, using the GEM-3D tool to add components not related to gas flow to the pipeline and shell solid models, establish a three-dimensional solid model of the intake and exhaust system, and then obtain a one-dimensional CFD simulation analysis model of the intake and exhaust system through discrete processing.

[0010] Furthermore, S1 specifically includes: importing the three-dimensional CAD model of the intake and exhaust system into the finite element software to convert it into a finite element model, and deleting the data of the components in the finite element model that are not related to the gas flow; the components that are not related to the gas flow include brackets, muffler fillers and porous media in the gas path.

[0011] Further, the finite element model is divided into a pipeline group and a shell group, and the extraction of the pipeline closed surface in S2 is specifically as follows: in the finite element software, the shell group is hidden, the inner surface of the pipeline group is extracted, the remaining geometric features of the pipeline group are deleted, and the openings at both ends of the pipeline are blocked using the surface to form the pipeline closed surface; the extraction of the shell closed surface in S2 is specifically as follows: in the finite element software, the pipeline group is hidden, the inner surface of the shell group is extracted, the remaining geometric features of the shell group are deleted, and the inner surface of the shell and the corresponding holes of the pipeline are blocked using the surface to form the shell closed surface.

[0012] Furthermore, in S2, triangular units are used to perform mesh processing on the pipeline closed surface and the shell closed surface respectively, and the size of the triangular units is 3-5 mm.

[0013] Furthermore, after the geometric model file of the pipeline closed surface is imported into the GT software, it is divided into multiple connection segments according to the geometric structure characteristics of the pipeline closed surface, and then each connection segment is converted into a straight pipe, curved pipe or bifurcated pipe solid model according to the structural characteristics.

[0014] Compared with the prior art, the present invention has the following beneficial effects.

[0015] 1. The present invention first establishes a finite element model that does not include components that are not related to gas flow, then extracts the pipeline closed surface and shell closed surface in the finite element model, respectively, performs mesh processing on the pipeline closed surface and shell closed surface, and exports them as geometric model files in STL format, which not only realizes the surface conversion of the finite element model, but also avoids the loss of structural features of the intake and exhaust system. Then, the GEM-3D tool of the GT software is used to convert the pipeline closed surface and shell closed surface into pipeline and shell solid models, and the components that are not related to gas flow are added to the pipeline and shell solid models again to establish a three-dimensional solid model of the intake and exhaust system, and then a one-dimensional CFD simulation analysis model of the intake and exhaust system is obtained through discrete processing, thereby ensuring the modeling accuracy. At the same time, compared with establishing a three-dimensional model of the intake and exhaust system in the GT software, the modeling efficiency of directly converting the pipeline closed surface and shell closed surface into pipeline and shell solid models is higher.

[0016] 2. The present invention imports the three-dimensional CAD model of the intake and exhaust system into the finite element software to convert it into a finite element model, and deletes the data of components in the finite element model that are not related to gas flow, making full use of the three-dimensional CAD model that has been completed by the design engineer in the early stage, and further improving the modeling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a modeling method of a one-dimensional CFD simulation analysis model of an automobile intake and exhaust system according to the present invention;

[0018] Figure 2 is a schematic diagram of the pipeline group of the present invention;

[0019] Figure 3 is a schematic diagram of the housing assembly of the present invention;

[0020] Figure 4 It is a schematic diagram of the pipeline and shell entity model described in the present invention.

[0021] In the figure, 1 is a pipe group, 11 is a pipe before silencer and a pipe inlet of the silencer, 12 is an internal pipe of the silencer, 13 is an outlet pipe of the silencer and a pipe after silencer, and 2 is a shell group. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0023] See also Figure 1 , the modeling method of the one-dimensional CFD simulation analysis model of the automobile intake and exhaust system shown in FIG. 1 includes the following steps:

[0024] S1, importing the three-dimensional CAD model of the intake and exhaust system into the Hypermesh software to convert it into a finite element model, and deleting the data of the components in the finite element model that are not related to the gas flow; the components that are not related to the gas flow include brackets, muffler fillers and porous media in the gas path, and obtaining a finite element model that does not include components that are not related to the gas flow.

[0025] S2, see Figure 2 and Figure 3 In the Hypermesh software, the finite element model is divided into a pipeline group 1 and a shell group 2. The pipeline group 1 includes a pre-muffler pipeline and a muffler inlet pipe 11, a muffler internal pipeline 12, a muffler outlet pipe, and a post-muffler pipeline 13. Then the shell group 2 is hidden, the inner surface of the pipeline group 1 is extracted, the remaining geometric features of the pipeline group 1 are deleted, and the openings at both ends of the pipeline are blocked with surfaces so that the pipeline group forms a pipeline closed surface. The pipeline closed surfaces are meshed using triangular units, and the size of the triangular units is 3 to 5 mm to obtain the meshed pipeline closed surfaces.

[0026] Then hide the pipeline group 1, extract the inner surface of the shell group 2, delete the remaining geometric features of the shell group 2, and use the surface to block the holes on the inner surface of the shell corresponding to the pipeline to form a shell closed surface. Use triangular units to mesh the shell closed surfaces respectively, and the size of the triangular units is 3-5mm to obtain the meshed shell closed surface.

[0027] Check the meshed pipeline closed surface and shell closed surface separately to prevent free edges from appearing in the mesh. Otherwise, these free edges need to be stitched to ensure that the obtained mesh surface is fully closed. After the inspection is completed, export the meshed pipeline closed surface and shell closed surface into STL format geometric model files respectively;

[0028] S3, open the GEM-3D tool, import the STL format geometric model file of the pipeline closed surface in the form of "Surface", and do not check "Center at origin" in the import option, that is, the pipeline closed surface is not placed with the origin as the center, ensuring that the relative position of the pipeline closed surface and the subsequent imported shell closed surface is the same as the relative position of the two in the finite element model. At the same time, specify the size unit of the STL format geometric model as mm according to the settings of the 3D CAD model.

[0029] In the GEM-3D tool, use "Marking mesh" to mark the network, hold down the "Ctrl" key and click on the end faces of each pipeline opening in the pipeline group. After the selection is completed, use the "Clip" tool to remove the end faces of the pipeline. Then divide the pipeline closed surface into multiple connection segments according to its geometric structural features, and then convert each connection segment into a straight pipe, curved pipe or bifurcated pipe solid model according to its structural features.

[0030] Import the STL format geometry model file of the shell closed surface in the "Surface" mode. Do not check "Center at origin" in the import options. Specify the dimension unit of the STL format geometry model as mm according to the settings of the 3D CAD model. Convert the shell closed surface to a shell solid model in the GEM-3D tool. Use the connection command to combine the pipeline solid model and the shell solid model.

[0031] S4, according to the design data of the muffler, the GEM-3D tool is used to add two partitions at the design position inside the shell solid model. The internal pipes of the shell solid model are perforated according to the design size, quantity and position. Finally, fillers are added to the cavity formed by the two partitions and the shell to simulate the muffler cotton. The connection ports and gas flow direction of the intake and exhaust system are specified, and a three-dimensional solid model of the intake and exhaust system is established. Then, a one-dimensional CFD simulation analysis model of the intake and exhaust system is obtained through discrete processing.

[0032] The present invention first establishes a finite element model that does not include components that are not related to gas flow, then extracts the pipeline closed surface and the shell closed surface in the finite element model respectively, performs mesh processing on the pipeline closed surface and the shell closed surface respectively, and exports them as geometric model files in STL format, which not only realizes the surface conversion of the finite element model, but also avoids the loss of structural characteristics of the intake and exhaust system. Then, the GEM-3D tool of the GT software is used to convert the pipeline closed surface and the shell closed surface into pipeline and shell solid models, and the components that are not related to gas flow are added to the pipeline and shell solid models again, and a three-dimensional solid model of the intake and exhaust system is established, and then a one-dimensional CFD simulation analysis model of the intake and exhaust system is obtained through discrete processing, thereby ensuring the modeling accuracy. At the same time, compared with establishing a three-dimensional model of the intake and exhaust system in the GT software, the modeling efficiency of directly converting the pipeline closed surface and the shell closed surface into the pipeline and shell solid model is higher. In addition, since the three-dimensional CAD model of the intake and exhaust system is imported into the finite element software and converted into a finite element model, the data of the components that are not related to gas flow in the finite element model are deleted, and the three-dimensional CAD model that the design engineer has completed in the early stage is fully utilized, further improving the modeling efficiency.

[0033] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A modeling method for a one-dimensional CFD simulation analysis model of an automobile intake and exhaust system, characterized in that: The steps include: S1, establishing a finite element model of an intake and exhaust system, wherein the finite element model does not include components irrelevant to gas flow; S2, dividing the finite element model into a pipeline group and a shell group, using finite element software to extract the pipeline closed surface in the finite element model and perform mesh processing on the pipeline closed surface. The extraction of the pipeline closed surface is specifically as follows: in the finite element software, hiding the shell group, extracting the inner surface of the pipeline group, deleting the remaining geometric features of the pipeline group, and plugging the openings at both ends of the pipeline using the surface to form the pipeline closed surface; Extract the shell closed surface in the finite element model and perform mesh processing on the shell closed surface. The extraction of the shell closed surface is as follows: in the finite element software, hide the pipeline group, extract the inner surface of the shell group, delete the remaining geometric features of the shell group, and use the surface to block the holes on the inner surface of the shell corresponding to the pipeline to form the shell closed surface; Export the meshed pipeline closed surface and shell closed surface into STL format geometric model files; S3, importing the geometric model files of the pipeline closed surface and the shell closed surface into the GT software, and using the GEM-3D tool of the GT software to convert the pipeline closed surface and the shell closed surface into pipeline and shell solid models; S4, using the GEM-3D tool to add components not related to gas flow to the pipeline and shell solid models, establish a three-dimensional solid model of the intake and exhaust system, and then obtain a one-dimensional CFD simulation analysis model of the intake and exhaust system through discrete processing.

2. The modeling method of the one-dimensional CFD simulation analysis model of the automobile intake and exhaust system according to claim 1 is characterized in that: Specifically, S1 includes: importing the three-dimensional CAD model of the intake and exhaust system into the finite element software to convert it into a finite element model, and deleting the data of the components in the finite element model that are not related to the gas flow; the components that are not related to the gas flow include brackets, muffler fillers and porous media in the gas path.

3. The modeling method of the one-dimensional CFD simulation analysis model of the automobile intake and exhaust system according to claim 1 or 2 is characterized in that: In S2, triangular units are used to perform mesh processing on the pipeline closed surface and the shell closed surface respectively, and the size of the triangular units is 3-5 mm.

4. The modeling method of the one-dimensional CFD simulation analysis model of the automobile intake and exhaust system according to claim 1 or 2 is characterized in that: After the geometric model file of the pipeline closed surface is imported into the GT software, it is divided into multiple connection segments according to the geometric structure characteristics of the pipeline closed surface, and then each connection segment is converted into a straight pipe, curved pipe or bifurcated pipe solid model according to the structural characteristics.

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