正负气压组合油菜精量排种器锥孔盘排种性能

为进一步提升正负气压组合式油菜精量排种器性能，该研究提出了一种可增加种群扰动、降低被吸附种子运移阻力的圆锥型孔排种盘。通过理论分析和离散元仿真试验阐明倒角截顶圆锥孔排种盘排种性能提升机理，并通过台架试验对排种性能提升效果进行了验证。理论分析表明，在排种盘上采用圆周密布的圆锥型孔，排种盘型孔临近吸种区域种群横向扰动增大，型孔上被吸附种子随排种盘运移时的切向阻力降低，利于提高充种成功率和携种稳定性。离散元仿真分析表明，相同型孔数条件下倒角截顶圆锥孔盘较圆直孔盘在充种室种群平均速度增大66.72%；在型孔附近临近吸种区种子切向运移速度提高90.45%，轴向运移速度增加83.90%，径向运移速度提高165.60%，吸附在型孔上的种子运动阻力下降35.60%。台架试验表明，在工作负压800～4 800 Pa、转速10～50 r/min条件下，倒角截顶圆锥孔排种盘较圆直孔排种盘单粒排种合格指数提高5.49%、重播指数及漏播指数分别降低68.62%和3.79%，在卸种正压200 Pa、工作负压2 100 Pa、转速25 r/min条件下，其合格指数、重播指数、漏播指数最高可达98.13%、1.25%和0.62%。倒角截顶圆锥孔排种盘在不增加附属搅种和充种装置的基础上，可有效提高单粒排种性能，降低排种器重播指数和漏播指数，提升排种器作业性能，研究结果可为正负气压组合式油菜精量排种器结构优化提供参考。

Seeding performance of conical-hole seeding plate of the positive and negative pressure combination precision seed metering device for rapeseed

Abstract: A seed-metering device has been widely applied with the combined positive and negative pressure in various agricultural machinery for medium and small-size seeding. However, the hole-type of seeding plate in the traditional device cannot match the seed size during filling, leading to the low carrying performance. It is a high demand for the high precision and efficiency of equipment for rapeseed seeding. In this study, a conical-hole seeding plate was proposed to increase the local population disturbance in the seed filling area, and reduce the transport resistance of the adsorbed seeds, further improving the operational performance of the precision metering device combined with the positive and negative pressure for the rapeseed in the medium-high speed sowing. The conical suction holes were also circularly distributed in the seeding plate, in order to increase the disturbance of the seed population in the seeding chamber, and the velocity of seed particles in the seed filling area near the holes. A comparison was also made on the seeding performance of the seed metering device with two types of seeding plate, such as the conical and cylindrical suction holes. The seed filling success and carrying stability were greatly improved using the seeding plate with conical suction holes, compared with the cylindrical holes, due to the low tangential resistance of the adsorbed seeds on the holes, when migrating along with the seeding plat. Discrete element simulation and quantitative analysis were implemented to compare the seeding plate with conical suction holes and cylindrical holes under the same number of holes. It was found that the average velocity of seed populations in the seeding chamber increased by 66.72% with the conical holes. Meanwhile, the velocities of seed particles in the seed filling area along the tangential, axial, and radial directions increased by 90.45%, 83.90%, and 165.60%, respectively. Specifically, the tangential resistance in the seed motion decreased by 35.60%, when the seeds were adsorbed on the holes. The bench test showed that the seed metering device with the conical-hole seeding plate greatly promoted the qualified index by 5.49%, but reduced the multiple and missing index by 68.62% and 3.79%, respectively, when the work negative pressure of the air chamber in the range of 800~4 800 Pa, and the rotating speed of seeding plate within 10~50 r/min. More importantly, the qualified, multiple and missing index reached 98.13%, 1.25%, and 0.62%, with the conical-hole seeding plate, under the working conditions of positive pressure in 200 Pa, negative pressure in 2 100 kPa, and the rotating speed of seeding plate in 25 r/min. Consequently, the conical-hole plate effectively improved the seeding performance of the precision seed-metering device without wedge churning and filling, where the holding performance of single seeding was enhanced to reduce the multiple and missing index. The conical-hole plate presented a much greater effective depth and area of seed contact than those of the cylindrical holes plate. The movement of the seed particles was facilitated to effectively implement the single seeds and holding, further to accurately take the single seed from the population and disturb the population. The findings can provide a strong reference for the structural optimization of the combined positive and negative pressure precision seed-metering device for the medium and small-size seeds and medium-high speed sowing.