| No-tillage sowing of corn is one of the main techniques of conservation tillage,which is directly fertilizing and sowing with no-tillage planter on the stubble land after corn straw returning.Deep fertilization makes the root system directly contact with fertilizer,which can effectively ensure the emergence rate and yield of seeds.Due to the poor performance of returning soil under the condition of deep fertilization,the sowing depth consistency of the sowing furrow opener is poor,the working resistance is large,and the soil disturbance is large,which seriously affects the sowing quality and cannot achieve the ideal operation effect.In order to improve the consistency of sowing depth,reduce working resistance and soil disturbance,and meet the agronomic requirements of sowing furrows under deep fertilization,this paper explores the performance and law of soil fallback under deep fertilization,fully considers the influence of different types of machines and tools on soil fallback in the process of stubble breaking and deep fertilization,and designs a segmented sowing furrow opener based on the simulation analysis of stubble breaking knife-fertilizing shovel device,extracting the dynamic movement track of soil.Comprehensive discrete element simulation,theoretical analysis,multi-objective optimization,field test and other methods and means,determine the structure parameters and working parameters of the ditcher,and verify and compare its operation effect and working performance,in order to provide reference for the design and theoretical research of ditcher.(1)Discrete element simulation test of pieces knife-fertilization shovel devicesA discrete element simulation model of soil-root-straw was established.Three common types of disc stubble cutters(flact type,notch type and corrugated type)and two common types of fertilizer shovels(sharp angle type and arc type type)were selected to make six stubble cutters-fertilizer shovels for discrete element simulation test.The influence of different types of stubble cutters-deep fertilization devices on soil dynamic motion trajectory was analyzed in depth,and the dynamic motion trajectory of soil was obtained as follows:down-up-start.The position and direction of the maximum force in the process of soil falling back after each stubble-breaking and deep fertilization device were extracted respectively,and six fitting curves representing the position and direction of the maximum force of soil falling back were obtained,which provided a theoretical basis for the design of ditcher.(2)Structure design and verification segmented sowing openerSectional sowing furrow opener is composed of two parts,which are buried and not buried.According to the optimization of six fitting curves,three fitting curves were obtained,and three kinds of curves(Ⅰ,Ⅱ,Ⅲ)of ditcher were designed.According to the sliding cutting principle,the optimal sliding cutting angle of the inclined edge of the trencher is 32.24 under the minimum power consumption,and the inclined edge of the trencher is designed.According to the time when the soil falls back from the beginning to the maximum force,the installation distance between the fertilizer shovel and three kinds of segmented sowing ditchers is determined to be 396 mm,360mm and 374 mm respectively.At the same time,through the discrete element simulation verification test,the rationality of the design idea is verified by comparing the direction of soil maximum force.(3)Field optimization experiment and validation of segmented sowing openerSelecting the forward speed,load and straw coverage of segmented sowing furrow opener as experimental factors,and taking the coefficient of variation of sowing depth,working resistance,disturbed area of soil and depth of returning soil as evaluation indexes,using Design-Expert 8.0.6software,adopting three factors and five levels quadratic orthogonal rotation center regression test method to carry out multi-objective optimization.When the forward speed of the furrow opener is4.81 km/h,the load is 0.08 k N,and the field straw coverage is 0.76 kg/m~2,the optimal results of the comprehensive operation performance of the segmented sowing furrow opener are as follows:the coefficient of variation of sowing depth is 6.22%,the working resistance is 76.65 N,the disturbed area of soil is 1064 mm~2,and the depth of returning soil is 41 mm,experiments are carried out under the optimal operation parameters to verify the accuracy of the optimized theoretical values.(4)Field contrast experiment of segmented sowing openerBased on the field optimization test results of the segmented sowing furrow opener,the field comparative tests were carried out between the segmented sowing furrow opener and the sharp angle furrow opener,the sliding knife opener and the double disc furrow opener.Taking the coefficient of variation of sowing depth,working resistance,disturbed area of soil and depth of returning soil as evaluation indexes.At the same time,SPSS software was used to analyze the variance and multiple comparisons of the test data.The test results showed that the staged sowing furrow opener had better operation performance,which could improve the consistency of sowing depth,reduce the working resistance and soil disturbance,and meet the requirements of no-tillage sowing operation.The segmented sowing furrow opener designed in this study meets the requirements of agricultural machinery and agronomy,and can effectively improve the quality of no-tillage sowing operation under deep fertilization,which provides corresponding reference for the design optimization and theoretical research of furrow opener. |
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