小麦气流辅助直线投种装置设计与试验

Design and Experiment of Air-assisted Linear Seeding Device for Wheat

摘要:

针对小麦精量匀播作业条件下气流辅助投种装置内部压力梯度变化方向与种子运动方向不一致、造成种子倒流或碰撞、降低粒距稳定性等问题，设计了一种小麦气流辅助直线投种装置。基于气-固两相流数学模型建立CFD-DEM单向耦合仿真模型模拟投种过程，仿真结果表明：入口气压与管道长度对总压损失及流场压力分布影响显著；投种装置内部流场压力分布均匀，压力梯度变化方向与种子运动方向一致；小麦种子运动轨迹为“直线-曲线-直线”，无倒流与碰撞现象。以入口气压、管道长度、作业速度为试验因素，以粒距变异系数为试验评价指标进行了响应曲面优化试验。试验结果表明：影响粒距变异系数因素的主次顺序为入口气压、作业速度、管道长度；入口气压与管道长度和作业速度均存在交互作用。通过参数优化得到较优参数组合为：入口气压5.1kPa、管道长度24.2cm、作业速度0.11m/s，经土槽试验验证，该条件下粒距变异系数为6.3%，平均粒距为5.3cm，满足小麦精量匀播农艺要求。采用气流辅助直线投种可解决小麦种子倒流与碰撞的问题，从而显著改善播种作业效果，为小麦精量匀播提供技术支撑。

Abstract:

An air-assisted linear seed seeding device for wheat was created in order to address the issue that the pressure gradient’s change direction in the air-assisted seed seeding device is inconsistent with the direction of seed movement, leading to seed backflow or collision and decreasing the stability of grain spacing. To simulate the seeding process, a CFD-DEM unidirectional coupling simulation model was developed, which was based on the mathematical model of gas-solid two-phase flow. According to the simulation results, the length of the pipeline and the inlet pressure had a big impact on the flow field’s pressure distribution and overall pressure loss. The seeding device’s flow field had a uniform pressure distribution, and the direction of the pressure gradient change corresponded with the direction in which the seeds migrated.Wheat seeds followed a “straight-curve-straight line” motion path that avoided collisions and backflow. Inlet pressure, pipeline length, and operating speed were used as test factors in the response surface optimization test, and the grain distance variation coefficient served as the test evaluation index. The test findings indicated that inlet pressure, operating speed, and pipeline length were the primary and secondary factors influencing the grain distance variation coefficient. Operating speed and pipe length were influenced by inlet pressure. Through parameter optimization, the following parameters were found to be the best combinations: operation speed of 0.11m/s, pipeline length of 24.2cm, and inlet pressure of 5.1kPa.The soil tank test confirmed that under these conditions, the average grain spacing was 5.3cm and the coefficient of grain spacing variation was 6.3%, meeting the agronomic requirements for precise, uniform wheat sowing. By addressing the issues of wheat seed backflow and collision, air-assisted linear seeding may greatly enhance seeding performance and offer technical assistance for accurate and consistent wheat sowing.