Maize Flexible Threshing Experiments And Parameter Optimization

Corn is a vital crop that serves as both a food source and an essential raw material for industrial production.In addition,it plays a crucial role in animal husbandry.In recent years,advancements in technology have led to the widespread adoption of direct grain harvesting,replacing traditional mechanical ear harvesting in many corn planting areas.However,in China’s corn-wheat continuous cropping areas,the use of direct grain harvesting technology has faced significant challenges.This is due to a range of factors,including the unique needs of China’s farming season,the characteristics of domestic corn varieties,and the high moisture content in the harvest period.As a result,the mechanized direct harvesting of corn grains has led to a high rate of damage and breakage,making it difficult to reduce losses.This issue poses a significant obstacle to the popularization and application of grain mechanized direct harvesting technology.Threshing is a critical component of corn harvesting,as it directly impacts the quality of harvested corn kernels and the safety of their storage.Broken kernels are more susceptible to mold,insect damage,and rot,which not only reduce their economic value but also have a significant impact on the overall quality and yield of the corn crop.Therefore,developing innovative threshing techniques to minimize corn damage during threshing is crucial.This paper aims to address the issue of high breakage rates during the direct harvesting of corn kernels in China.Building on previous research in threshing technology,the paper proposes a new flexible threshing method that leverages the advantages of flexible threshing.To minimize grain damage during threshing and improve the reliability and safety of the operation,the paper also develops a control system based on the internal control of the threshing drum.The flexible threshing structure is then combined with an understanding of the change in corn kernel damage resistance strength,leading to the development of a flexible threshing control strategy and technology based on variable stiffness.Finally,the paper conducts research and verification of the single ear threshing test to explore the flexible threshing technology of corn with variable stiffness.The study demonstrates that flexible threshing with variable stiffness has the potential to significantly reduce the rate of grain damage,providing a valuable technical reference for the continued development of direct harvesting technology for corn grain in China.The research content of this paper is outlined as follows:(1)Measured and analyzed the basic characteristic parameters of corn kernels in the optimum harvest period,mainly including the length(L),width(W),thickness(T)and water content(ω)of the kernels.Based on these parameters,geometric diameter(Dg)and sphericity(φ)were analyzed.The experiment found that there are differences in the moisture content of the grains in different parts of the ear,and the morphological characteristics of the grains also vary with the change of the ear axis.In addition,the damage mechanical properties of different corn varieties and different parts of the ear under different force application methods were analyzed to provide a reference for corn flexible threshing technology.(2)Through the theoretical analysis of grain threshing mechanics under single grain,single row multi-seed and tangential multi-seed support,and experimental research on grain threshing mechanics.The test results show that the support form of the grain has a significant effect on the tangential threshing force of the grain.In the absence of support,the tangential threshing force of a single grain is the smallest;with the increase of the number of tangentially and axially supported grains,the threshing force will increase in different degrees.(3)Based on the Hertz contact theory,a mechanical model of contact between the flexible threshing element and maize kernels was established,which theoretically proved the effectiveness of the flexible threshing element in reducing kernel damage;and based on the team’s previous flexible threshing research,a variable stiffness flexible threshing technology was proposed;through the analysis of the variable stiffness flexible technology,a variable stiffness truncated cone spring was designed.(4)A single-ear corn threshing test bench was built,and the single-ear corn threshing test was carried out.The effects of threshing speed,threshing gap and contact angle on grain threshing force and grain damage rate were analyzed through orthogonal experiment.Through the analysis of corn grain breakage,it is shown that: threshing speed,threshing gap and contact angle have a significant impact on the grain breakage rate;The optimum combination of threshing speed of 150 r/min,a threshing gap of 1/2 of the kernel length,and a contact angle of90° were determined.The effectiveness of the flexible threshing element in reducing kernel damage was verified by comparing the threshing effect of the conventional spiked tooth threshing element with that of the flexible threshing element.The tests show that flexible threshing with variable stiffness has some potential to achieve low-damage harvesting of maize kernels and the findings further improve the theory of flexible threshing.