油菜气动射播排种器设计与试验

Design and Experiment of Pneumatic Shooting Seeder for Rapeseed

摘要:

针对常规油菜联合精量播种机触土部件易粘附土壤和双圆盘开沟器等导致开种沟装置开种沟深度不稳定、出苗不均匀等问题，本文设计了一种负压吸种、正压高速射种的油菜气动射播排种器。确定了喷嘴半径、加速管半径、加速管长度、加速管与喷嘴距离等关键参数，分析了喷射器结构与种子速度对流场总压力损失的影响因素;构建了种子与射播排种器第2次碰撞方程和动力学方程，分析了射播排种器混合腔内涡流面积对种子第2次碰撞后轨迹的影响;应用CFD-DEM耦合仿真开展了三因素三水平正交试验，分别构建喷射系数、射出平均速度、混合腔涡流面积比回归模型，得到最优结构参数为：喷嘴半径6.9 mm、嘴管距13.8 mm、加速管半径10.36 mm，此时喷射系数为0.314，种子射出平均速度为20.92 m/s，混合腔涡流面积比为21.15%;台架验证试验结果表明，较优结构参数下，未出现种子滞留现象，同时确定了土壤含水率为30%和45%时，风机速度为35 m/s、射播排种器距离土壤高度为150 mm时，排种性能较优;当土壤含水率为35%和40%时，风机速度为40 m/s和射播排种器距离土壤高度为150 mm，排种性能较优。田间试验结果表明，当土壤含水率为38.5%时，油菜各行植株分布在种行宽度为120 mm内的平均概率为80.12%，植株密度为66株/m2，满足油菜精量播种要求。

Abstract:

Considering the problem that the inconsistent furrow depths generated by soil contact parts plugging and double disc openers of existing precision planter for rapeseed in the furrows, resulting in uneven emergence, a pneumatic shooting seeder for rapeseed with seed extraction with negative pressure suction and positive pressure high-speed seeding was designed. The key parameter ranges of nozzle radius, accelerating pipe radius, accelerating pipe length and distance between accelerating pipe and nozzle were determined. The effects of seeder structure and seed velocity on the total pressure loss of flow field were also analyzed. The dynamic model and the corresponding collision equations for the second collision between seeds and seeder was established. The influence of the vortex area in the mixing chamber of the seeder on the trajectory of seeds after their second collision was analyzed. A three-factor and three-level orthogonal experimental study was conducted using CFD-DEM coupled simulation. Regression models were established for the ejection coefficient, seed average shooting velocity, and vortex area ratio in the mixing chamber. It was determined that when the nozzle radius was 6.9 mm, distance between accelerating pipe and nozzle was 13.8 mm, and accelerating pipe radius of 10.36 mm were the optimal structural parameters, The injection coefficient was 0.314, the seed average shooting velocity was 20.92 m/s, and the vortex area ratio in the mixing chamber was 21.15%. It was verified by bench test that there was no seed retention phenomenon under the optimal structural parameters of the seeder. And it also determined the following optimal operating conditions: with soil moisture contents of 30% and 45%, the fan speed was set to be 35 m/s and the height of the seeder above the soil surface was 150 mm;with soil moisture contents of 35% and 40%, the fan speed was set to be 40 m/s and the seeder height was maintained at 150 mm. Field experiment results showed that when the soil water content was 38.5%, the average probability of each line of rapeseed distributed within 120 mm seed row width was 80.12%, and the plant density was 66 plants/m2, which met the requirements of precision sowing of rapeseed.