In order to reduce working resistance of seeding opener and soil disturbance,the opener based on bionic sailfish head curve was designed.The two-dimensional (2D) drafting software of CATIA (computer aided three-dimensional interactive application) is used for getting the sailfish head profile curve.The head profile curve segments of sailfish is obtained based on the relative positional coordinates of points.Using the agronomic requirements and the parameters of the head profile curve segments of sailfish determine the structural parameters of opener.The main structure parameters of the opener are penetration angle of 30° and penetration clearance angle of 6°.Due to the interaction of the soil and the opener during movement is a complex process,the discrete element simulation from microscopic point of view is performed to study the interaction between the opener and the soil.The discrete element model of soil is established.In order to ensure the accuracy of test data,the related parameters are calibrated.Soil resistance is influenced by working depth and soil moisture content.At the same time,the relationship between working depth and soil disturbance is obtained.The software of EDEM (enhanced discrete element method) is used for the simulation analysis of working resistance and soil disturbance of the opener.Soil moisture content is 12％±1％,16％±1％,and 20％±1％,working depth is 30,60,and 90 mm,respectively,and forward speed of the opener is 0.5 m/s.Under these working conditions,the working resistance of the opener and its disturbance to soil are studied.Simulation results show that the working resistance of the opener increases with the increasing of soil moisture content,and also increases with the increasing of ditching depth,the horizontal resistance is between 19.70 and 74.60 N,the vertical resistance is between 9.37 and 26.90 N,the width of the disturbance in the opener is between 140 and 200 mm,and the soil returning depth is between 19 and 80 mm.In order to prove the credibility of the simulation results of the EDEM and the rationality of the opener,the experiments are carried out in the agricultural soil test laboratory of the northeast agricultural university.Simulation of work resistance and test results showed that the trend of change in work resistance was roughly the same,the relative error were between 5.04％ and 27.08％.Compared with the experimental results,the simulation results were almost the same as the experimental results,and the difference of the ditching depth was between-2.5 and 0.67 mm,but thesimulation results of the disturbance width were between 106.7 and 140 mm,smaller than the experimental results,which may be related to the larger particle size of the simulated particles.The trend was basically the same.The opener based on bionic sailfish head curve and the arc-type opener were selected for contrast experiment.The results showed that the performance of the opener based on bionic sailfish head curve was better than the arc-type opener.The research shows the feasibility of using the discrete element method to simulate opener's working resistance and soil disturbance,and provides a convenient method for the opener design.%为了减小播种开沟器的工作阻力,降低其对土壤的扰动,根据旗鱼头部的流线型曲线,建立了拟合曲线的数学模型,设计了仿旗鱼头部曲线型开沟器.为获得该开沟器工作时工作阻力及其对土壤扰动情况,进行离散元仿真和室内土槽试验.在前进速度为0.5 m/s时,分别以3种土壤含水率、3种开沟器开沟深度为因素进行仿真及室内试验.仿真结果:在含水率为12％±1％时,工作阻力、对土壤扰动宽度和回土深度随开沟深度的增加呈增加趋势;在开沟深度为60 mm时,工作阻力随含水率的增加而增加,但对土壤扰动宽度、回土深度影响不明显.工作阻力仿真与试验结果对比,两者变化趋势大致相同,相对误差在5.04％～27.08％之间.土壤扰动情况仿真与试验结果对比:回土深度的仿真与试验结果接近,而土壤扰动宽度的仿真与试验结果差别较大,可能是土壤颗粒粒径较大引起的,但变化趋势基本一致.由此说明了采用离散元法模拟开沟器的工作阻力及其对土壤扰动情况的可行性.该文可为开沟器的设计与优化提供参考.
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