基于EDEM软件的指夹式精量排种器排种性能数值模拟与试验

为研究玉米籽粒尺寸及工作转速对指夹式精量排种器排种性能的影响,对排种器工作原理进行阐述,建立了指夹夹持动力学模型,分析了充种夹持过程中玉米籽粒尺寸及工作转速对指夹夹持性能的影响。运用EDEM软件进行排种性能虚拟试验,分析了排种过程中造成不同尺寸等级籽粒产生重播、漏播问题的主要原因。仿真结果表明,当工作转速15~45 r/min时,排种器对中型尺寸籽粒的排种性能最优,其合格指数大于84%;对大型尺寸籽粒的排种性能次之;对小型尺寸籽粒的排种性能较差,其合格指数大于80%。随工作转速增加,排种器对各尺寸等级籽粒的排种性能皆呈下降趋势。在相同工况(15~45 r/min)下选取3种相应尺寸等级玉米籽粒,进行台架验证试验。结果表明,台架试验结果与仿真基本相同,合格指数最大误差为7.4%,且排种性能随玉米籽粒尺寸及工作转速的变化规律一致。田间试验表明,排种器对各尺寸等级籽粒的排种性能皆满足精密播种要求。该研究为指夹式精量排种器及其关键部件的优化设计提供了参考。

Numerical simulation and experiment on seeding performance of pickup finger precision seed-metering device based on EDEM

Abstract: Precision planting is the advanced technology that sows seeds in the predetermined position of soil accurately and quantitatively by precision planter. Precision metering device is the key component of precision planter, which is divided into 2 types according to the working principle. The one is mechanical metering device, and the other type is pneumatic metering device. Pickup finger precision seed-metering device is a kind of mechanical metering device, which has been increasingly widespread due to its advantages of high planting quality, low seed-injuring rate and good uniformity when sowing corn grains. Studies have shown that corn grain's size has a greater influence on the seeding performance. However, most corn grains are irregular in shape, which can cause the clamping performance of key component (pickup seed finger) to descend when operation at high speed. Therefore, studies on the motion characteristics of corn grains and the influences of rotational speed and size grade are meaningful to improve seeding performance. The pickup finger precision seed-metering device was studied in this paper based on the theory of discrete element method (DEM). The dynamical clamping models of pickup seed finger were established based on its working principle. On this basis, the optimization design of structural parameters of pickup seed finger was conducted. The DEM model of pickup finger precision seed-metering device was established by the discrete element software EDEM and the numerical simulation of seeding performance was carried out. The rotational speed and the size grade were selected as influencing factors, and the qualified index, the repeated index and the missing index were selected as experimental indices. The main causes of repeated seeding and missing seeding on different size grades of corn grains were researched. The simulation results showed that as the rotational speed was between 15 and 45 r/min, the seeding quantity of medium-size grains was the best, and the qualified index was greater than 84%, followed by that of large-size grains. The seeding quantity of small-size grains was the worst and its qualified index was greater than 80%. With the increase of the rotational speed, the seeding quantity had a decreasing trend to all size grades of corn grains. Under the same condition (15-45 r/min), 3 kinds of corn grains were selected and the bench test was done. The test results showed that the simulation results were consistent with the bench test results, the maximum error of qualified indices was 7.4%, and the changing trends of seeding performance with rotational speed and size grade between simulation experiments and bench tests were also consistent. The field test showed that, when the rotational speed was 35 r/min and the forward velocity was 7 km/h, the seeding performance of seed-metering device could meet the requirements of precision sowing for all size grades of corn grains. The results in this paper can provide the guidance and direction for the research of mechanical precision seed-metering device and its key parts.