Improvement Research Of Corn Threshing Process Simulation Software

During the corn harvesting process,a special threshing machine is required to separate the corn kernels from the corn cob.It can be seen that the performance of the threshing machine directly affects the final corn harvesting yield.When researching corn threshing machinery at home and abroad,the test method and continuous medium mechanical analysis method are mainly used,which are not very efficient,and the actual situation of corn threshing in actual production cannot be accurately simulated.The research group has developed a simulation software that uses discrete element method to simulate corn threshing process.Based on this,combining with computational fluid dynamics theory,the original corn threshing process simulation software has been improved.The paper redesigned the overall architecture of the original threshing software,accomplish the integration of the threshing software with the new discrete element method software developed by the research group,and improved the shortcomings of the threshing software.In the simulation threshing process,the corn ear model established by the original threshing software includes corn kernels and corn cobs,but the grain gap existing on the real corn cannot be simulated.In order to make the simulation results more consistent with the real threshing process,this article adds corn kernel clearance parameter setting function.Moreover,the original threshing process calculation code still has some problems,which cause the corn kernels to jittering and flying when they fall from corn cob to the boundary,or crashes during neighbor search.This article made changes to the threshing calculation code,by selecting a new formula for calculating the moment of inertia of corn kernels,the phenomenon of jittering and flying of the kernels was successfully solved,and the problem of software crashes during the neighbor search was avoided.In view of the large number of parameters involved in the use of software simulation by users,the test efficiency of manual setting is extremely low,so the article improves the threshing parameter setting interface,and adds the function of saving and querying threshing simulation parameters,allowing users to quickly find the simulation set in the simulation process,to analyze and compare the corresponding simulation parameters of multiple sets of simulation results.After the threshing software simulation calculation is completed,it is necessary to open the generated simulation result file for performance analysis,observe the force of each component on the threshing machine,and then analyze and improve the component design work of the threshing machine.The original software can only observe the combined forces of the components in the global coordinate system when they are subjected to forces on the components,and their analysis capabilities are limited.In order to improve the analysis ability of the software,this paper accomplishes the functions of calculating the boundary force and the boundary moment in any coordinate system by establishing a new local coordinate system and a transformation matrix between the local coordinate system and the global coordinate system.In the actual analysis process,when the number of mechanical component boundaries is large,the boundary force analysis process of the original software consumes a lot of time and affects the analysis efficiency of the software.Reducing save operation significantly improves the speed of software analysis of boundary forces.The original software required the fluid to always exist when simulating the calculation of the fluid.The loading time of the fluid could not be set freely,resulting in a smaller application range of the software to simulate the fluid.In the follow-up improvement work,the software has added the timing loading function of the fluid simulation to allow the user to set the initial loading time and the continuous movement time of the fluid,which greatly improves the flexibility of the CFD simulation calculation function.In the process of corn threshing,some technologies such as pneumatic cleaning are used when some threshing machinery is working.Therefore,the paper also adds a fluid computing function to simulate the corn threshing process.By treating the corn grains as a sphere,combining the simulated fluid and sphere coupling motion method accomplishes the DEM-CFD coupling calculation function of corn threshing process.In the later stage of software development,the maintenance cost is getting higher and higher.Considering that the dynamic link library technology provided by Microsoft can assist in the modular design and development of the code,reduce the repetitive labor of developers,and facilitate the maintenance of later projects,this article chooses to use the dynamic link library.This technology encapsulates CFD simulation calculation modules,improves the development efficiency of simulation software,and reduces conflicts between different modules.Aiming at the above improvement work,this paper designs multiple sets of corresponding test cases.Taking into account the segmental structure characteristics of the corn model,this paper tested the simulation calculation process of single-segment corn,intact corn,and individual corn kernels.The test results show that: when use DEM-CFD coupled simulation of corn threshing process,the trajectory of corn particle movement will be deflected by the fluid force.After the corn kernels fall to the boundary,there will be no more continuous fluttering.The CFD timing loading function limits the particles to the fluid force only during the fluid loading time,and other time periods the particles are only affected by the contact force caused by gravity and collision.When analyzing the boundary force,by setting multiple sets of different local coordinate systems,the boundary force can be transformed into any direction,and the boundary moment in that direction can be solved.According to the above test results,it shows that the improved threshing software can more accurately simulate the corn threshing process,and the performance analysis capability of the mechanical parts of the simulation results is also significantly improved.