A fast convergence method for simulation of pressure-bearing performance of soft interlayer of solid pulse engine

Abstract

The present invention relates to the research field of solid rocket engine technology, and specifically to a method for rapid convergence of simulation of the pressure-bearing performance of a soft interlayer of a solid pulse engine. The steps are as follows: S1: Using conventional simulation methods, reduce the load to ensure the convergence of the simulation model; S2: Extract the deformed geometric model through secondary development; S3: Re-grid the deformed geometric model to improve the quality of the grid; S4: Map the calculation results of the first step to the re-grid, and apply the complete load for solution calculation to obtain the simulation result. The present invention provides a method for rapid convergence of simulation of the pressure-bearing performance of a soft interlayer of a solid pulse engine. The method can effectively improve the distortion of the grid during the solution process, and can improve the convergence of the simulation model without a large number of trial calculations, saving a lot of time cost, and has good versatility, providing technical support for the development of solid pulse engines.

Description

Technical Field

[0001] The invention relates to the research field of solid rocket engine technology, and in particular to a fast convergence method for simulating the pressure bearing performance of a soft interlayer of a solid pulse engine. Background Art

[0002] The soft interlayer is an important component of the solid pulse engine. Its pressure bearing capacity and opening process are the key to the start-stop control and energy management of the pulse engine. When the first pulse is working, the interlayer relies on the second pulse grain to bear the pressure, playing a role of heat insulation and sealing. When the second pulse is working, the interlayer breaks in the designed weak area, and then the broken interlayer cone section flips back and opens. The soft interlayer has the advantages of light weight, good processability, and controllable flying objects, which can meet the development needs of future advanced pulse engines. There is usually a certain gap between the interlayer and the second pulse grain. When under pressure, the interlayer bends and attaches to the second pulse grain, and deforms together with the grain. This design method provides a certain deformation space for the interlayer and also provides a gas channel for the second pulse combustion chamber. When performing pressure bearing performance simulation analysis, the interlayer and the second pulse grain will undergo large deformation, and the grid will be distorted as the structure deforms. This process involves problems such as large structural deformation and boundary nonlinearity, which requires extremely high grid adaptability and particularly harsh simulation convergence conditions. In engineering, commercial finite element software is directly used to simulate the pressure-bearing performance of the interlayer, which is prone to the problem of solution divergence caused by grid distortion. Simulation engineers can only continuously adjust the grid layout and perform multiple trial calculations to improve the convergence of the simulation model as much as possible. However, the grid adjustment strategy of this method is difficult to clarify. Too large or too small a grid size may lead to solution divergence. Even if it can be adjusted appropriately in the end, it will take a lot of time and cost, and it cannot meet the rapid demonstration requirements of solid pulse engines. Some engineers adopt methods such as increasing the mechanical performance parameters of materials or reducing pressure loads to alleviate grid distortion, but no matter which method is adopted, it is equivalent to changing the state of the simulation model, which is inconsistent with the actual engineering problem, and the role it can play in the structural design and performance evaluation of the interlayer is very limited. In view of the above reasons, the present invention combines secondary development technology with node mapping technology to avoid grid distortion in the grid solution process, improve the convergence of the simulation model, greatly improve the work efficiency of interlayer simulation, and provide important technical support for the research and development of solid pulse engines.

[0003] At present, the main approach used in engineering is to continuously adjust the grid layout and perform multiple trial calculations to improve the convergence of the simulation model for the pressure-bearing performance of soft interlayers.

[0004] The shortcomings of using existing technologies to simulate the pressure-bearing performance of soft interlayers are as follows: First, adjusting the grid layout cannot guarantee the convergence of the simulation model. Due to the high sensitivity of grid distortion, a slightly larger or smaller angle or size of the grid may lead to non-convergence of the solution, and there is no regularity. This makes it almost impossible for simulation engineers to have any strategy when adjusting the grid layout, and they can only rely on "taking a chance" and keep trying. Even if most models have been adjusted many times, their convergence is still not guaranteed; secondly, adjusting the grid layout requires a lot of time and cost. When dividing the mesh, the geometric model needs to be cut and simplified to varying degrees. Even if the topological structure of the geometric model is not changed, it takes a certain amount of time to adjust the mesh size. Each time the mesh is adjusted, a simulation trial calculation must be performed, which causes the time spent on the simulation to double. Secondly, if the mechanical properties of the material are artificially increased or the pressure load is reduced, the convergence of the simulation model can be improved to a certain extent, but this method makes the simulation model inconsistent with the actual state, making it difficult to estimate the pressure-bearing performance of the interlayer, and the guiding role in the interlayer structure design is minimal. Finally, due to the lack of a method for simulating the pressure-bearing performance of the soft interlayer, when the designer is demonstrating the scheme, in order to ensure the pressure-bearing performance of the interlayer, he has to artificially increase the design margin to ensure the safety and reliability of the structure, but this will reduce the overall performance of the engine. In summary, this technical bottleneck has become one of the key factors restricting the effective improvement of the engine research and development level. Summary of the invention

[0005] Technical Problems to be Solved by the Invention

[0006] The present invention provides a method for rapid convergence of simulation of pressure bearing performance of a soft barrier of a solid rocket engine, so as to solve the above-mentioned existing shortcomings.

[0007] Technical solution to the problem The technical solution adopted by the present invention

[0008] A fast convergence method for simulation of pressure bearing performance of soft interlayer of solid pulse engine, the operation steps are as follows:

[0009] S1: Use conventional simulation methods to reduce the load and ensure the convergence of the simulation model;

[0010] S2: Extract the deformed geometric model through secondary development;

[0011] S3: Re-mesh the deformed geometric model to improve the quality of the mesh;

[0012] S4: Map the calculation results of the first step to the re-divided grid, apply the full load for solution calculation, and then you can get the simulation results.

[0013] Furthermore, the step of S1:

[0014] S11: Import the solid pulse engine geometry model into the commercial finite element software in the form of "assembly", merge the shell, insulation layer, grain and partition into an independent part, and ensure that the dividing lines between the structures are common edges;

[0015] S12: Create corresponding material properties and specify the cross-sectional properties of each structure;

[0016] S13: Select a reasonable unit size for meshing according to the size of the model;

[0017] S14: Create a static analysis step, check the restart option, and set the general contact relationship;

[0018] S15: When loading, only a suitable small load is applied to the model. After solving, the simulation results under the small load can be obtained. At this time, the mesh has been deformed but the deformation is not serious.

[0019] Furthermore, the specific operation of S2 is to splice meshes of the same material through a secondary development method to form a series of new geometric bodies, and finally extract the deformation geometric model under a small load.

[0020] Furthermore, the step of S2 is:

[0021] S21: If the extraction fails, reduce the load, jump back to S1, find a suitable load, and continue;

[0022] S22: If the extraction is successful, continue to merge the deformed geometric model, specify the same section properties as the first step, select the same unit size to re-divide the regular grid, set the same standard contact, and apply the full load.

[0023] Furthermore, the specific operation of S4 is to modify the INP file of the new simulation model and add the Map Solution related command keywords; submit the calculation through the command line, enter the job name of the first step in the old job name, and the simulation results of the first step can be mapped to the new grid through node mapping.

[0024] Furthermore, the step S4:

[0025] S41: If the solution diverges, reduce the load and repeat step S1;

[0026] S42: If the solution converges, the simulation results of the pressure bearing performance of the soft interlayer under the full load can be obtained.

[0027] Beneficial effects obtained by the present invention

[0028] According to the simulation method of the pressure bearing performance of soft interlayers in engineering, the present invention conforms to the development trend of informatization of domestic work processes, and is based on the actual demand for estimating the pressure bearing performance of interlayers in the development process of solid pulse engines. A set of fast convergence methods for simulating the pressure bearing performance of soft interlayers of solid pulse engines has been developed. This method can effectively avoid the divergence problem of solution caused by grid distortion, improve the convergence of the simulation model without a large number of trial calculations, reduce the difficulty of simulating the pressure bearing performance of interlayers, reduce the time required for simulation, significantly improve the demonstration speed of solid pulse engines, shorten the development cycle of solid pulse engine products to a certain extent, and has important guiding significance for the improvement and development of solid pulse engine design technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 :Flowchart of rapid convergence method for simulation of pressure-bearing performance of soft interlayer of solid pulse engine;

[0030] Figure 2 : Local mesh image before deformation;

[0031] Figure 3 : Local image of mesh after deformation;

[0032] Figure 4 :Re-grid local map;

[0033] Figure 5 : Local diagram of equivalent stress calculation results. DETAILED DESCRIPTION

[0034] The present invention provides a fast convergence method for simulating the pressure-bearing performance of a soft interlayer of a solid pulse engine. The method can effectively improve the distortion of the grid during the solution process, and can improve the convergence of the simulation model without a large number of trial calculations, thereby saving a large amount of time cost. The method has good versatility and provides technical support for the development of solid pulse engines.

[0035] In order to make the purpose, features and advantages of the technical solution proposed in the present invention more obvious and easy to understand, the embodiments of the technical solution proposed in the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the proposed technical solution, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0036] like Figure 1As shown in the figure, the rapid convergence method flow of the simulation of the pressure-bearing performance of the soft interlayer of the solid pulse engine. The geometric model of the solid pulse engine is imported into the commercial finite element software in the form of "assembly", and the structures such as the shell, insulation layer, grain column and interlayer are merged into an independent part to ensure that the dividing lines between the structures are common edges; create corresponding material properties and specify the cross-sectional properties of each structure; select a reasonable unit size for meshing according to the size of the model; create a static analysis step, check the restart option, and set the general contact relationship; only apply a suitable small load to this model during loading, and the simulation results under small load can be obtained after solving. At this time, the mesh has been deformed but the deformation is not serious.

[0037] Import the above calculation results into the newly created simulation model. At this time, the part type in the model is a deformed isolated grid. Through the secondary development method, the grids of the same material are spliced ​​together to form a series of new geometric bodies, and finally the deformed geometric model under small load can be extracted. If the extraction fails, reduce the load and repeat the above steps; if the extraction is successful, continue to merge the deformed geometric model, specify the same section properties as the first step, select the same unit size to re-divide the regular grid, set the same standard contact, and apply the full load. Modify the INP file of the new simulation model and add the Map Solution related command keywords. Submit the calculation through the command line, enter the job name of the first step in the old job name, and the simulation results of the first step can be mapped to the new grid by node mapping. If the solution diverges, reduce the load and repeat the above steps; if the solution converges, the simulation results of the pressure bearing performance of the soft interlayer under the full load can be obtained.

[0038] like Figure 2 The figure shows a partial mesh before deformation. The pulse engine geometry model is imported into commercial finite element software, and geometric simplification and meshing are performed to obtain a regular mesh, i.e., the mesh before deformation.

[0039] like Figure 3 As shown in the figure, the mesh is partially deformed. After applying a suitable small load to the simulation model, the mesh will be deformed, and some of the mesh has changed from quadrilaterals to triangles. Since the deformation is not serious enough, it is not enough to cause the simulation to not converge. However, if the load is further increased on this basis, the mesh will be distorted, which will lead to divergence of the solution.

[0040] like Figure 4 As shown, the mesh is partially re-divided. The deformed mesh is processed by secondary development, and then the deformed geometric model is extracted. The deformed geometric model is meshed to obtain a re-divided mesh. At this time, the mesh is relatively regular and of high quality.

[0041] like Figure 5As shown in Figure 1, the equivalent stress calculation results are partial. The calculation results of the first step are mapped to the re-divided grid, and the full load is applied. After solving, the equivalent stress calculation results can be obtained to estimate whether the current solid pulse engine combustion chamber design is reasonable.

[0042] In the specific implementation, ① first use the conventional simulation method to reduce the load to ensure the convergence of the simulation model; ② extract the deformed geometric model through secondary development; ③ re-divide the deformed geometric model to improve the quality of the mesh; ④ map the calculation results of the first step to the re-divided mesh, and apply the complete load for solution calculation, then the simulation result can be obtained, which improves the convergence of the simulation model.

[0043] The present invention summarizes the general method of simulating the pressure bearing performance of solid pulse engines, introduces secondary development methods and node mapping methods, significantly improves the convergence of the simulation model, avoids the simulation engineer's repeated adjustment of the grid layout and multiple trial calculations of the simulation model, greatly reduces the operation time, and significantly improves the work efficiency. In addition, the present invention does not rely on the specific size of the solid pulse engine combustion chamber, and can be applied to the pressure bearing simulation process of the soft interlayer of the conventional solid pulse engine, and has good versatility.

[0044] The present invention has been widely used within the unit, providing important technical support for the development of solid pulse engines, greatly improving design efficiency, shortening the development time of the engine to a certain extent, and having obvious application value.

Claims

1. A method for rapid convergence of simulation of pressure bearing performance of soft interlayer of solid pulse engine, characterized in that: The steps are as follows: S1: Use conventional simulation methods to reduce the load and ensure the convergence of the simulation model. Specifically: S11: Import the solid pulse engine geometry model into the commercial finite element software in the form of "assembly", merge the shell, insulation layer, grain and partition into an independent part, and ensure that the dividing lines between the structures are common edges; S12: Create corresponding material properties and specify the cross-sectional properties of each structure; S13: Select a reasonable unit size for meshing according to the size of the model; S14: Create a static analysis step, check the restart option, and set the general contact relationship; S15: When loading, only a suitable small load is applied to the model. After solving, the simulation result under the small load can be obtained. At this time, the mesh has been deformed but the deformation is not serious. S2: Extract the deformed geometric model through secondary development; S3: Re-mesh the deformed geometric model to improve the quality of the mesh; S4: Map the calculation results of the first step to the re-divided grid, apply the full load for solution calculation, and then you can get the simulation results.

2. According to claim 1, a method for rapid convergence of simulation of pressure bearing performance of soft interlayer of solid pulse engine is characterized by: The specific operation of S2 is to splice the meshes of the same material through a secondary development method to form a series of new geometric bodies, and finally extract the deformation geometric model under a small load.

3. The method for rapid convergence of simulation of pressure bearing performance of soft interlayer of solid pulse engine according to claim 1 is characterized in that: The steps of S2 are: S21: If the extraction fails, reduce the load, jump back to S1, find a suitable load, and continue; S22: If the extraction is successful, continue to merge the deformed geometric model, specify the same section properties as the first step, select the same unit size to re-divide the regular grid, set the same standard contact, and apply the full load.

4. The method for rapid convergence of simulation of pressure bearing performance of soft interlayer of solid pulse engine according to claim 1 is characterized by: The specific operation of S4 is to modify the INP file of the new simulation model and add the command keywords related to Map Solution; Submit the calculation through the command line, enter the job name of the first step in the old job name, and the simulation results of the first step can be mapped to the new grid through node mapping.

5. The method for rapid convergence of simulation of pressure bearing performance of soft interlayer of solid pulse engine according to claim 4 is characterized in that: The S4 step: S41: If the solution diverges, reduce the load and repeat step S1; S42: If the solution converges, the simulation results of the pressure bearing performance of the soft interlayer under the full load can be obtained.

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