基于离散元法的免耕深施肥分段式玉米播种开沟器研制

Development of deep fertilizing no-tillage segmented maize sowing opener using discrete element method

针对东北垄作深施肥免耕播种机上开沟器播种深度均匀性差、工作阻力大、土壤扰动大的问题,该研究利用离散元软件(EDEM 2.7)仿真分析不同类型破茬刀-施肥铲装置对土壤的作用机理,设计了一种分段式玉米播种开沟器。首先建立土壤-玉米根系-玉米秸秆离散元仿真模型,然后进行不同类型破茬刀-施肥铲装置离散元仿真试验,以回落土壤最大合外力的位置和方向为依据设计开沟器入土部分曲线,同时结合滑切原理设计开沟器未入土部分斜刃,最后根据土壤回落距离确定施肥铲和开沟器间距为374 mm。田间对比试验结果表明,分段式开沟器比尖角式开沟器、滑刀式开沟器、双圆盘式开沟器的播深变异系数分别降低了14.24%、27.31%、33.63%;工作阻力分别降低了27.56%、16.93%、1.23%;土壤扰动面积分别降低了11.67%、28.34%、49.34%。分段式开沟器播种深度均匀性高、工作阻力小、土壤扰动小,具有较优的作业效果。

Openers in no-tillage can confer a yield benefit via disruption of pathogenic hyphae,particularly when crop rotations lack species diversity in extremely cold climates,like in northeast China.However,it is still urgent to improve the uniformity of seedling depth,while alleviating large working resistance and soil disturbance on the deep fertilizing no-tillage planter after returning crop stalks to the field.In this study,a novel opener was designed for corn seeds in a segmented flow for deep fertilizing and no-tillage using a Discrete Element Method(DEM).Six types of stubble cutter-fertilization shovel devices were selected on the soil to explore the effect mechanism in the simulated analysis.First of all,a soil-corn stubble-corn straw DEM model was established to achieve the uniform seed-to-soil contact.Three kinds of stubble cutters(including plane,notched and corrugated stubble cutter)were then randomly combined with two kinds of fertilization shovels(including sharp and arc-type fertilization shovel)in the DEM simulation test.After that,a respective analysis was carried out for the motion trail of soil particles in the six types of stubble cutter–fertilization shovel devices after the operation.The location and direction of soil particles were finally extracted to obtain six fitted curves representing the maximum force in the falling process.As such,the curve of the opener was designed in the buried part.Specifically,the opener curveⅠwas set as the fitted falling curve of soil particles after the combination operation of three kinds of stubble cutters and sharp-cornered fertilization shovel devices.The opener curveⅡwas that of three kinds of stubble cutters and arc-type fertilization shovel devices.The opener curveⅢwas that of six kinds of stubble cutters and fertilization shovel devices.At the same time,the inclined edge of the opener in the unburied part was also designed to improve the passing ability,particularly for the sliding frictional angle under the minimum power consumption when cutting straw.In addition,the buried clearance angle of the opener was set as 6°with the traverse width of 20 mm and inclined edge angle of 30°.Finally,the optimal spacing between the fertilization shovel and the opener was determined as 374 mm,according to the time and advanced speed for the soil particle falling back to the maximum force.Besides,a field test was performed on three kinds of segmented openers to verify the feasibility of the developed device.CurveⅢwas finally chosen in the buried part for more extensive applicability of the segmented opener.The field comparison test indicated that the variable coefficient of seedling depth in the segmented opener dropped 14.24%,27.31%,and 33.63%,respectively,while the working resistance dropped 27.56%,16.93%,and 1.23%,respectively,as well as 11.67%,28.34%,and 49.34%in the soil disturbance area,compared with the sharp-cornered,the sliding knife and double disk opener.Consequently,a high operation performance was achieved in the segmented opener,including high uniformity of seedling depth,small working resistance,and soil disturbance for deep fertilizing and no-tillage.